pc: acpi: revert back to 1 SRAT entry for hotpluggable area

Commit
  10efd7e108 "pc: acpi: fix memory hotplug regression by reducing stub SRAT entry size"
attemped to fix hotplug regression introduced by
  848a1cc1e "hw/acpi-build: build SRAT memory affinity structures for DIMM devices"

fixed issue for Windows/3.0+ linux kernels, however it regressed 2.6 based
kernels (RHEL6) to the point where guest might crash at boot.
Reason is that 2.6 kernel discards SRAT table due too small last entry
which down the road leads to crashes. Hack I've tried in 10efd7e108 is also
not ACPI spec compliant according to which whole possible RAM should be
described in SRAT. Revert 10efd7e108 to fix regression for 2.6 based kernels.

With 10efd7e108 reverted, I've also tried splitting SRAT table statically
in different ways %/node and %/slot but Windows still fails to online
2nd pc-dimm hot-plugged into node 0 (as described in 10efd7e108) and
sometimes even coldplugged pc-dimms where affected with static SRAT
partitioning.
The only known so far way where Windows stays happy is when we have 1
SRAT entry in the last node covering all hotplug area.

Revert 848a1cc1e until we come up with a way to avoid regression
on Windows with hotplug area split in several entries.
Tested this with 2.6/3.0 based kernels (RHEL6/7) and WS20[08/12/12R2/16]).

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
---
CC: haozhong.zhang@intel.com
CC: mst@redhat.com
CC: qemu-stable@nongnu.org
CC: ehabkost@redhat.com
CC: lersek@redhat.com
---
 hw/i386/acpi-build.c | 73 +++++++++-------------------------------------------
 1 file changed, 12 insertions(+), 61 deletions(-)

On 08/22/18 11:46, Igor Mammedov wrote:
> Commit
>   10efd7e108 "pc: acpi: fix memory hotplug regression by reducing stub SRAT entry size"
> attemped to fix hotplug regression introduced by
>   848a1cc1e "hw/acpi-build: build SRAT memory affinity structures for DIMM devices"
> 
> fixed issue for Windows/3.0+ linux kernels, however it regressed 2.6 based
> kernels (RHEL6) to the point where guest might crash at boot.
> Reason is that 2.6 kernel discards SRAT table due too small last entry
> which down the road leads to crashes. Hack I've tried in 10efd7e108 is also
> not ACPI spec compliant according to which whole possible RAM should be
> described in SRAT. Revert 10efd7e108 to fix regression for 2.6 based kernels.
> 
> With 10efd7e108 reverted, I've also tried splitting SRAT table statically
> in different ways %/node and %/slot but Windows still fails to online
> 2nd pc-dimm hot-plugged into node 0 (as described in 10efd7e108) and
> sometimes even coldplugged pc-dimms where affected with static SRAT
> partitioning.
> The only known so far way where Windows stays happy is when we have 1
> SRAT entry in the last node covering all hotplug area.
> 
> Revert 848a1cc1e until we come up with a way to avoid regression
> on Windows with hotplug area split in several entries.
> Tested this with 2.6/3.0 based kernels (RHEL6/7) and WS20[08/12/12R2/16]).
> 
> Signed-off-by: Igor Mammedov <imammedo@redhat.com>
> ---
> CC: haozhong.zhang@intel.com
> CC: mst@redhat.com
> CC: qemu-stable@nongnu.org
> CC: ehabkost@redhat.com
> CC: lersek@redhat.com
> ---
>  hw/i386/acpi-build.c | 73 +++++++++-------------------------------------------
>  1 file changed, 12 insertions(+), 61 deletions(-)
> 
> diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
> index e1ee8ae..1599caa 100644
> --- a/hw/i386/acpi-build.c
> +++ b/hw/i386/acpi-build.c
> @@ -2251,64 +2251,6 @@ build_tpm2(GArray *table_data, BIOSLinker *linker, GArray *tcpalog)
>  #define HOLE_640K_START  (640 * KiB)
>  #define HOLE_640K_END   (1 * MiB)
>  
> -static void build_srat_hotpluggable_memory(GArray *table_data, uint64_t base,
> -                                           uint64_t len, int default_node)
> -{
> -    MemoryDeviceInfoList *info_list = qmp_memory_device_list();
> -    MemoryDeviceInfoList *info;
> -    MemoryDeviceInfo *mi;
> -    PCDIMMDeviceInfo *di;
> -    uint64_t end = base + len, cur, size;
> -    bool is_nvdimm;
> -    AcpiSratMemoryAffinity *numamem;
> -    MemoryAffinityFlags flags;
> -
> -    for (cur = base, info = info_list;
> -         cur < end;
> -         cur += size, info = info->next) {
> -        numamem = acpi_data_push(table_data, sizeof *numamem);
> -
> -        if (!info) {
> -            /*
> -             * Entry is required for Windows to enable memory hotplug in OS
> -             * and for Linux to enable SWIOTLB when booted with less than
> -             * 4G of RAM. Windows works better if the entry sets proximity
> -             * to the highest NUMA node in the machine at the end of the
> -             * reserved space.
> -             * Memory devices may override proximity set by this entry,
> -             * providing _PXM method if necessary.
> -             */
> -            build_srat_memory(numamem, end - 1, 1, default_node,
> -                              MEM_AFFINITY_HOTPLUGGABLE | MEM_AFFINITY_ENABLED);
> -            break;
> -        }
> -
> -        mi = info->value;
> -        is_nvdimm = (mi->type == MEMORY_DEVICE_INFO_KIND_NVDIMM);
> -        di = !is_nvdimm ? mi->u.dimm.data : mi->u.nvdimm.data;
> -
> -        if (cur < di->addr) {
> -            build_srat_memory(numamem, cur, di->addr - cur, default_node,
> -                              MEM_AFFINITY_HOTPLUGGABLE | MEM_AFFINITY_ENABLED);
> -            numamem = acpi_data_push(table_data, sizeof *numamem);
> -        }
> -
> -        size = di->size;
> -
> -        flags = MEM_AFFINITY_ENABLED;
> -        if (di->hotpluggable) {
> -            flags |= MEM_AFFINITY_HOTPLUGGABLE;
> -        }
> -        if (is_nvdimm) {
> -            flags |= MEM_AFFINITY_NON_VOLATILE;
> -        }
> -
> -        build_srat_memory(numamem, di->addr, size, di->node, flags);
> -    }
> -
> -    qapi_free_MemoryDeviceInfoList(info_list);
> -}
> -
>  static void
>  build_srat(GArray *table_data, BIOSLinker *linker, MachineState *machine)
>  {
> @@ -2414,10 +2356,19 @@ build_srat(GArray *table_data, BIOSLinker *linker, MachineState *machine)
>          build_srat_memory(numamem, 0, 0, 0, MEM_AFFINITY_NOFLAGS);
>      }
>  
> +    /*
> +     * Entry is required for Windows to enable memory hotplug in OS
> +     * and for Linux to enable SWIOTLB when booted with less than
> +     * 4G of RAM. Windows works better if the entry sets proximity
> +     * to the highest NUMA node in the machine.
> +     * Memory devices may override proximity set by this entry,
> +     * providing _PXM method if necessary.
> +     */
>      if (hotplugabble_address_space_size) {
> -        build_srat_hotpluggable_memory(table_data, machine->device_memory->base,
> -                                       hotplugabble_address_space_size,
> -                                       pcms->numa_nodes - 1);
> +        numamem = acpi_data_push(table_data, sizeof *numamem);
> +        build_srat_memory(numamem, machine->device_memory->base,
> +                          hotplugabble_address_space_size, pcms->numa_nodes - 1,
> +                          MEM_AFFINITY_HOTPLUGGABLE | MEM_AFFINITY_ENABLED);
>      }
>  
>      build_header(linker, table_data,
> 

So this reverts both 10efd7e108 (which only moved the regression around)
and the earlier 848a1cc1e (which had introduced the regression in the
first place).

If I understand correctly, the issue that 848a1cc1e was meant to solve
was that "-device nvdimm,node=..." could be passed by the user such that
it lead to "proximity domain mismatch". (What was the higher-level goal
with that BTW?)

However, that mismatch could as well be avoided by simply not passing
such "node=..." properties. Is that right?

If so, should we perhaps add another patch (temporarily), beyond this
revert, that identifies the misconfig in question, and prints a warning
about it?

Anyway the revert seems justified to me.

Acked-by: Laszlo Ersek <lersek@redhat.com>

Thanks
Laszlo

On Wed, 22 Aug 2018 12:06:26 +0200
Laszlo Ersek <lersek@redhat.com> wrote:

> On 08/22/18 11:46, Igor Mammedov wrote:
> > Commit
> >   10efd7e108 "pc: acpi: fix memory hotplug regression by reducing stub SRAT entry size"
> > attemped to fix hotplug regression introduced by
> >   848a1cc1e "hw/acpi-build: build SRAT memory affinity structures for DIMM devices"
> > 
> > fixed issue for Windows/3.0+ linux kernels, however it regressed 2.6 based
> > kernels (RHEL6) to the point where guest might crash at boot.
> > Reason is that 2.6 kernel discards SRAT table due too small last entry
> > which down the road leads to crashes. Hack I've tried in 10efd7e108 is also
> > not ACPI spec compliant according to which whole possible RAM should be
> > described in SRAT. Revert 10efd7e108 to fix regression for 2.6 based kernels.
> > 
> > With 10efd7e108 reverted, I've also tried splitting SRAT table statically
> > in different ways %/node and %/slot but Windows still fails to online
> > 2nd pc-dimm hot-plugged into node 0 (as described in 10efd7e108) and
> > sometimes even coldplugged pc-dimms where affected with static SRAT
> > partitioning.
> > The only known so far way where Windows stays happy is when we have 1
> > SRAT entry in the last node covering all hotplug area.
> > 
> > Revert 848a1cc1e until we come up with a way to avoid regression
> > on Windows with hotplug area split in several entries.
> > Tested this with 2.6/3.0 based kernels (RHEL6/7) and WS20[08/12/12R2/16]).
> > 
> > Signed-off-by: Igor Mammedov <imammedo@redhat.com>
> > ---
> > CC: haozhong.zhang@intel.com
> > CC: mst@redhat.com
> > CC: qemu-stable@nongnu.org
> > CC: ehabkost@redhat.com
> > CC: lersek@redhat.com
> > ---
> >  hw/i386/acpi-build.c | 73 +++++++++-------------------------------------------
> >  1 file changed, 12 insertions(+), 61 deletions(-)
> > 
> > diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
> > index e1ee8ae..1599caa 100644
> > --- a/hw/i386/acpi-build.c
> > +++ b/hw/i386/acpi-build.c
> > @@ -2251,64 +2251,6 @@ build_tpm2(GArray *table_data, BIOSLinker *linker, GArray *tcpalog)
> >  #define HOLE_640K_START  (640 * KiB)
> >  #define HOLE_640K_END   (1 * MiB)
> >  
> > -static void build_srat_hotpluggable_memory(GArray *table_data, uint64_t base,
> > -                                           uint64_t len, int default_node)
> > -{
> > -    MemoryDeviceInfoList *info_list = qmp_memory_device_list();
> > -    MemoryDeviceInfoList *info;
> > -    MemoryDeviceInfo *mi;
> > -    PCDIMMDeviceInfo *di;
> > -    uint64_t end = base + len, cur, size;
> > -    bool is_nvdimm;
> > -    AcpiSratMemoryAffinity *numamem;
> > -    MemoryAffinityFlags flags;
> > -
> > -    for (cur = base, info = info_list;
> > -         cur < end;
> > -         cur += size, info = info->next) {
> > -        numamem = acpi_data_push(table_data, sizeof *numamem);
> > -
> > -        if (!info) {
> > -            /*
> > -             * Entry is required for Windows to enable memory hotplug in OS
> > -             * and for Linux to enable SWIOTLB when booted with less than
> > -             * 4G of RAM. Windows works better if the entry sets proximity
> > -             * to the highest NUMA node in the machine at the end of the
> > -             * reserved space.
> > -             * Memory devices may override proximity set by this entry,
> > -             * providing _PXM method if necessary.
> > -             */
> > -            build_srat_memory(numamem, end - 1, 1, default_node,
> > -                              MEM_AFFINITY_HOTPLUGGABLE | MEM_AFFINITY_ENABLED);
> > -            break;
> > -        }
> > -
> > -        mi = info->value;
> > -        is_nvdimm = (mi->type == MEMORY_DEVICE_INFO_KIND_NVDIMM);
> > -        di = !is_nvdimm ? mi->u.dimm.data : mi->u.nvdimm.data;
> > -
> > -        if (cur < di->addr) {
> > -            build_srat_memory(numamem, cur, di->addr - cur, default_node,
> > -                              MEM_AFFINITY_HOTPLUGGABLE | MEM_AFFINITY_ENABLED);
> > -            numamem = acpi_data_push(table_data, sizeof *numamem);
> > -        }
> > -
> > -        size = di->size;
> > -
> > -        flags = MEM_AFFINITY_ENABLED;
> > -        if (di->hotpluggable) {
> > -            flags |= MEM_AFFINITY_HOTPLUGGABLE;
> > -        }
> > -        if (is_nvdimm) {
> > -            flags |= MEM_AFFINITY_NON_VOLATILE;
> > -        }
> > -
> > -        build_srat_memory(numamem, di->addr, size, di->node, flags);
> > -    }
> > -
> > -    qapi_free_MemoryDeviceInfoList(info_list);
> > -}
> > -
> >  static void
> >  build_srat(GArray *table_data, BIOSLinker *linker, MachineState *machine)
> >  {
> > @@ -2414,10 +2356,19 @@ build_srat(GArray *table_data, BIOSLinker *linker, MachineState *machine)
> >          build_srat_memory(numamem, 0, 0, 0, MEM_AFFINITY_NOFLAGS);
> >      }
> >  
> > +    /*
> > +     * Entry is required for Windows to enable memory hotplug in OS
> > +     * and for Linux to enable SWIOTLB when booted with less than
> > +     * 4G of RAM. Windows works better if the entry sets proximity
> > +     * to the highest NUMA node in the machine.
> > +     * Memory devices may override proximity set by this entry,
> > +     * providing _PXM method if necessary.
> > +     */
> >      if (hotplugabble_address_space_size) {
> > -        build_srat_hotpluggable_memory(table_data, machine->device_memory->base,
> > -                                       hotplugabble_address_space_size,
> > -                                       pcms->numa_nodes - 1);
> > +        numamem = acpi_data_push(table_data, sizeof *numamem);
> > +        build_srat_memory(numamem, machine->device_memory->base,
> > +                          hotplugabble_address_space_size, pcms->numa_nodes - 1,
> > +                          MEM_AFFINITY_HOTPLUGGABLE | MEM_AFFINITY_ENABLED);
> >      }
> >  
> >      build_header(linker, table_data,
> >   
> 
> So this reverts both 10efd7e108 (which only moved the regression around)
> and the earlier 848a1cc1e (which had introduced the regression in the
> first place).
> 
> If I understand correctly, the issue that 848a1cc1e was meant to solve
> was that "-device nvdimm,node=..." could be passed by the user such that
> it lead to "proximity domain mismatch". (What was the higher-level goal
> with that BTW?)
> 
> However, that mismatch could as well be avoided by simply not passing
> such "node=..." properties. Is that right?
>
> If so, should we perhaps add another patch (temporarily), beyond this
> revert, that identifies the misconfig in question, and prints a warning
> about it?
not exactly, before the patch node=... influenced only _PXM which is supposed
to be evaluated after SRAT table and override whatever was in static table.

The patch, as I understood it, was about ACPI spec compliance where nvdimm SPA
in NFIT table should have a corresponding entry in SRAT table with
MEM_AFFINITY_NON_VOLATILE flag set.
Whether it solves any real issues aren't known to me and typically for
Intel contributed patches, author's email doesn't exists anymore so ...
And even if it fixes some new nvdimm issue, I'd rather have it broken
than regress memory hotplug that worked fine so far and wait for another
nvdimm patch that won't break existing features.

> Anyway the revert seems justified to me.
I've killed quite enough time trying to find out a way to keep
everyone happy, but alas it's time to give up and let interested
party to deal with regressions while introducing new stuff for
nvdimm, hence this revert.

> Acked-by: Laszlo Ersek <lersek@redhat.com>
> Thanks
> Laszlo
>

On Wed, Aug 22, 2018 at 03:05:36PM +0200, Igor Mammedov wrote:
> On Wed, 22 Aug 2018 12:06:26 +0200
> Laszlo Ersek <lersek@redhat.com> wrote:
> 
> > On 08/22/18 11:46, Igor Mammedov wrote:
> > > Commit
> > >   10efd7e108 "pc: acpi: fix memory hotplug regression by reducing stub SRAT entry size"
> > > attemped to fix hotplug regression introduced by
> > >   848a1cc1e "hw/acpi-build: build SRAT memory affinity structures for DIMM devices"
> > > 
> > > fixed issue for Windows/3.0+ linux kernels, however it regressed 2.6 based
> > > kernels (RHEL6) to the point where guest might crash at boot.
> > > Reason is that 2.6 kernel discards SRAT table due too small last entry
> > > which down the road leads to crashes. Hack I've tried in 10efd7e108 is also
> > > not ACPI spec compliant according to which whole possible RAM should be
> > > described in SRAT. Revert 10efd7e108 to fix regression for 2.6 based kernels.
> > > 
> > > With 10efd7e108 reverted, I've also tried splitting SRAT table statically
> > > in different ways %/node and %/slot but Windows still fails to online
> > > 2nd pc-dimm hot-plugged into node 0 (as described in 10efd7e108) and
> > > sometimes even coldplugged pc-dimms where affected with static SRAT
> > > partitioning.
> > > The only known so far way where Windows stays happy is when we have 1
> > > SRAT entry in the last node covering all hotplug area.
> > > 
> > > Revert 848a1cc1e until we come up with a way to avoid regression
> > > on Windows with hotplug area split in several entries.
> > > Tested this with 2.6/3.0 based kernels (RHEL6/7) and WS20[08/12/12R2/16]).
> > > 
> > > Signed-off-by: Igor Mammedov <imammedo@redhat.com>
> > > ---
> > > CC: haozhong.zhang@intel.com
> > > CC: mst@redhat.com
> > > CC: qemu-stable@nongnu.org
> > > CC: ehabkost@redhat.com
> > > CC: lersek@redhat.com
> > > ---
> > >  hw/i386/acpi-build.c | 73 +++++++++-------------------------------------------
> > >  1 file changed, 12 insertions(+), 61 deletions(-)
> > > 
> > > diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
> > > index e1ee8ae..1599caa 100644
> > > --- a/hw/i386/acpi-build.c
> > > +++ b/hw/i386/acpi-build.c
> > > @@ -2251,64 +2251,6 @@ build_tpm2(GArray *table_data, BIOSLinker *linker, GArray *tcpalog)
> > >  #define HOLE_640K_START  (640 * KiB)
> > >  #define HOLE_640K_END   (1 * MiB)
> > >  
> > > -static void build_srat_hotpluggable_memory(GArray *table_data, uint64_t base,
> > > -                                           uint64_t len, int default_node)
> > > -{
> > > -    MemoryDeviceInfoList *info_list = qmp_memory_device_list();
> > > -    MemoryDeviceInfoList *info;
> > > -    MemoryDeviceInfo *mi;
> > > -    PCDIMMDeviceInfo *di;
> > > -    uint64_t end = base + len, cur, size;
> > > -    bool is_nvdimm;
> > > -    AcpiSratMemoryAffinity *numamem;
> > > -    MemoryAffinityFlags flags;
> > > -
> > > -    for (cur = base, info = info_list;
> > > -         cur < end;
> > > -         cur += size, info = info->next) {
> > > -        numamem = acpi_data_push(table_data, sizeof *numamem);
> > > -
> > > -        if (!info) {
> > > -            /*
> > > -             * Entry is required for Windows to enable memory hotplug in OS
> > > -             * and for Linux to enable SWIOTLB when booted with less than
> > > -             * 4G of RAM. Windows works better if the entry sets proximity
> > > -             * to the highest NUMA node in the machine at the end of the
> > > -             * reserved space.
> > > -             * Memory devices may override proximity set by this entry,
> > > -             * providing _PXM method if necessary.
> > > -             */
> > > -            build_srat_memory(numamem, end - 1, 1, default_node,
> > > -                              MEM_AFFINITY_HOTPLUGGABLE | MEM_AFFINITY_ENABLED);
> > > -            break;
> > > -        }
> > > -
> > > -        mi = info->value;
> > > -        is_nvdimm = (mi->type == MEMORY_DEVICE_INFO_KIND_NVDIMM);
> > > -        di = !is_nvdimm ? mi->u.dimm.data : mi->u.nvdimm.data;
> > > -
> > > -        if (cur < di->addr) {
> > > -            build_srat_memory(numamem, cur, di->addr - cur, default_node,
> > > -                              MEM_AFFINITY_HOTPLUGGABLE | MEM_AFFINITY_ENABLED);
> > > -            numamem = acpi_data_push(table_data, sizeof *numamem);
> > > -        }
> > > -
> > > -        size = di->size;
> > > -
> > > -        flags = MEM_AFFINITY_ENABLED;
> > > -        if (di->hotpluggable) {
> > > -            flags |= MEM_AFFINITY_HOTPLUGGABLE;
> > > -        }
> > > -        if (is_nvdimm) {
> > > -            flags |= MEM_AFFINITY_NON_VOLATILE;
> > > -        }
> > > -
> > > -        build_srat_memory(numamem, di->addr, size, di->node, flags);
> > > -    }
> > > -
> > > -    qapi_free_MemoryDeviceInfoList(info_list);
> > > -}
> > > -
> > >  static void
> > >  build_srat(GArray *table_data, BIOSLinker *linker, MachineState *machine)
> > >  {
> > > @@ -2414,10 +2356,19 @@ build_srat(GArray *table_data, BIOSLinker *linker, MachineState *machine)
> > >          build_srat_memory(numamem, 0, 0, 0, MEM_AFFINITY_NOFLAGS);
> > >      }
> > >  
> > > +    /*
> > > +     * Entry is required for Windows to enable memory hotplug in OS
> > > +     * and for Linux to enable SWIOTLB when booted with less than
> > > +     * 4G of RAM. Windows works better if the entry sets proximity
> > > +     * to the highest NUMA node in the machine.
> > > +     * Memory devices may override proximity set by this entry,
> > > +     * providing _PXM method if necessary.
> > > +     */
> > >      if (hotplugabble_address_space_size) {
> > > -        build_srat_hotpluggable_memory(table_data, machine->device_memory->base,
> > > -                                       hotplugabble_address_space_size,
> > > -                                       pcms->numa_nodes - 1);
> > > +        numamem = acpi_data_push(table_data, sizeof *numamem);
> > > +        build_srat_memory(numamem, machine->device_memory->base,
> > > +                          hotplugabble_address_space_size, pcms->numa_nodes - 1,
> > > +                          MEM_AFFINITY_HOTPLUGGABLE | MEM_AFFINITY_ENABLED);
> > >      }
> > >  
> > >      build_header(linker, table_data,
> > >   
> > 
> > So this reverts both 10efd7e108 (which only moved the regression around)
> > and the earlier 848a1cc1e (which had introduced the regression in the
> > first place).
> > 
> > If I understand correctly, the issue that 848a1cc1e was meant to solve
> > was that "-device nvdimm,node=..." could be passed by the user such that
> > it lead to "proximity domain mismatch". (What was the higher-level goal
> > with that BTW?)
> > 
> > However, that mismatch could as well be avoided by simply not passing
> > such "node=..." properties. Is that right?
> >
> > If so, should we perhaps add another patch (temporarily), beyond this
> > revert, that identifies the misconfig in question, and prints a warning
> > about it?
> not exactly, before the patch node=... influenced only _PXM which is supposed
> to be evaluated after SRAT table and override whatever was in static table.
> 
> The patch, as I understood it, was about ACPI spec compliance where nvdimm SPA
> in NFIT table should have a corresponding entry in SRAT table with
> MEM_AFFINITY_NON_VOLATILE flag set.
> Whether it solves any real issues aren't known to me and typically for
> Intel contributed patches, author's email doesn't exists anymore so ...
> And even if it fixes some new nvdimm issue, I'd rather have it broken
> than regress memory hotplug that worked fine so far and wait for another
> nvdimm patch that won't break existing features.
> 
> > Anyway the revert seems justified to me.
> I've killed quite enough time trying to find out a way to keep
> everyone happy, but alas it's time to give up and let interested
> party to deal with regressions while introducing new stuff for
> nvdimm, hence this revert.

If the original author isn't available, I agree the best option
is to revert it to avoid the regression by now.

Reviewed-by: Eduardo Habkost <ehabkost@redhat.com>

However, have you considered keeping adding separate entries for
NVDIMM devices only (so we follow the spec), but add a single
(numa_nodes-1, MEM_AFFINITY_HOTPLUGGABLE|MEM_AFFINITY_ENABLED)
entry to the rest?

This way both use cases should still work as expected.  If
Windows break if using NVDIMM + Memory Hotplug at the same time,
maybe that's just a Windows bug we can't work around.

CCing NVDIMM maintainer, and Intel people who may be able to
help.

Summary: SRAT changes added for NVDIMM break memory hotplug on
Windows, and our best option right now is to revert the changes.


On Wed, Aug 22, 2018 at 11:46:44AM +0200, Igor Mammedov wrote:
> Commit
>   10efd7e108 "pc: acpi: fix memory hotplug regression by reducing stub SRAT entry size"
> attemped to fix hotplug regression introduced by
>   848a1cc1e "hw/acpi-build: build SRAT memory affinity structures for DIMM devices"
> 
> fixed issue for Windows/3.0+ linux kernels, however it regressed 2.6 based
> kernels (RHEL6) to the point where guest might crash at boot.
> Reason is that 2.6 kernel discards SRAT table due too small last entry
> which down the road leads to crashes. Hack I've tried in 10efd7e108 is also
> not ACPI spec compliant according to which whole possible RAM should be
> described in SRAT. Revert 10efd7e108 to fix regression for 2.6 based kernels.
> 
> With 10efd7e108 reverted, I've also tried splitting SRAT table statically
> in different ways %/node and %/slot but Windows still fails to online
> 2nd pc-dimm hot-plugged into node 0 (as described in 10efd7e108) and
> sometimes even coldplugged pc-dimms where affected with static SRAT
> partitioning.
> The only known so far way where Windows stays happy is when we have 1
> SRAT entry in the last node covering all hotplug area.
> 
> Revert 848a1cc1e until we come up with a way to avoid regression
> on Windows with hotplug area split in several entries.
> Tested this with 2.6/3.0 based kernels (RHEL6/7) and WS20[08/12/12R2/16]).
> 
> Signed-off-by: Igor Mammedov <imammedo@redhat.com>
> ---
> CC: haozhong.zhang@intel.com
> CC: mst@redhat.com
> CC: qemu-stable@nongnu.org
> CC: ehabkost@redhat.com
> CC: lersek@redhat.com
> ---
>  hw/i386/acpi-build.c | 73 +++++++++-------------------------------------------
>  1 file changed, 12 insertions(+), 61 deletions(-)
> 
> diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
> index e1ee8ae..1599caa 100644
> --- a/hw/i386/acpi-build.c
> +++ b/hw/i386/acpi-build.c
> @@ -2251,64 +2251,6 @@ build_tpm2(GArray *table_data, BIOSLinker *linker, GArray *tcpalog)
>  #define HOLE_640K_START  (640 * KiB)
>  #define HOLE_640K_END   (1 * MiB)
>  
> -static void build_srat_hotpluggable_memory(GArray *table_data, uint64_t base,
> -                                           uint64_t len, int default_node)
> -{
> -    MemoryDeviceInfoList *info_list = qmp_memory_device_list();
> -    MemoryDeviceInfoList *info;
> -    MemoryDeviceInfo *mi;
> -    PCDIMMDeviceInfo *di;
> -    uint64_t end = base + len, cur, size;
> -    bool is_nvdimm;
> -    AcpiSratMemoryAffinity *numamem;
> -    MemoryAffinityFlags flags;
> -
> -    for (cur = base, info = info_list;
> -         cur < end;
> -         cur += size, info = info->next) {
> -        numamem = acpi_data_push(table_data, sizeof *numamem);
> -
> -        if (!info) {
> -            /*
> -             * Entry is required for Windows to enable memory hotplug in OS
> -             * and for Linux to enable SWIOTLB when booted with less than
> -             * 4G of RAM. Windows works better if the entry sets proximity
> -             * to the highest NUMA node in the machine at the end of the
> -             * reserved space.
> -             * Memory devices may override proximity set by this entry,
> -             * providing _PXM method if necessary.
> -             */
> -            build_srat_memory(numamem, end - 1, 1, default_node,
> -                              MEM_AFFINITY_HOTPLUGGABLE | MEM_AFFINITY_ENABLED);
> -            break;
> -        }
> -
> -        mi = info->value;
> -        is_nvdimm = (mi->type == MEMORY_DEVICE_INFO_KIND_NVDIMM);
> -        di = !is_nvdimm ? mi->u.dimm.data : mi->u.nvdimm.data;
> -
> -        if (cur < di->addr) {
> -            build_srat_memory(numamem, cur, di->addr - cur, default_node,
> -                              MEM_AFFINITY_HOTPLUGGABLE | MEM_AFFINITY_ENABLED);
> -            numamem = acpi_data_push(table_data, sizeof *numamem);
> -        }
> -
> -        size = di->size;
> -
> -        flags = MEM_AFFINITY_ENABLED;
> -        if (di->hotpluggable) {
> -            flags |= MEM_AFFINITY_HOTPLUGGABLE;
> -        }
> -        if (is_nvdimm) {
> -            flags |= MEM_AFFINITY_NON_VOLATILE;
> -        }
> -
> -        build_srat_memory(numamem, di->addr, size, di->node, flags);
> -    }
> -
> -    qapi_free_MemoryDeviceInfoList(info_list);
> -}
> -
>  static void
>  build_srat(GArray *table_data, BIOSLinker *linker, MachineState *machine)
>  {
> @@ -2414,10 +2356,19 @@ build_srat(GArray *table_data, BIOSLinker *linker, MachineState *machine)
>          build_srat_memory(numamem, 0, 0, 0, MEM_AFFINITY_NOFLAGS);
>      }
>  
> +    /*
> +     * Entry is required for Windows to enable memory hotplug in OS
> +     * and for Linux to enable SWIOTLB when booted with less than
> +     * 4G of RAM. Windows works better if the entry sets proximity
> +     * to the highest NUMA node in the machine.
> +     * Memory devices may override proximity set by this entry,
> +     * providing _PXM method if necessary.
> +     */
>      if (hotplugabble_address_space_size) {
> -        build_srat_hotpluggable_memory(table_data, machine->device_memory->base,
> -                                       hotplugabble_address_space_size,
> -                                       pcms->numa_nodes - 1);
> +        numamem = acpi_data_push(table_data, sizeof *numamem);
> +        build_srat_memory(numamem, machine->device_memory->base,
> +                          hotplugabble_address_space_size, pcms->numa_nodes - 1,
> +                          MEM_AFFINITY_HOTPLUGGABLE | MEM_AFFINITY_ENABLED);
>      }
>  
>      build_header(linker, table_data,
> -- 
> 2.7.4
>

On Wed, 22 Aug 2018 15:01:12 -0300
Eduardo Habkost <ehabkost@redhat.com> wrote:

> On Wed, Aug 22, 2018 at 03:05:36PM +0200, Igor Mammedov wrote:
> > On Wed, 22 Aug 2018 12:06:26 +0200
> > Laszlo Ersek <lersek@redhat.com> wrote:
> >   
> > > On 08/22/18 11:46, Igor Mammedov wrote:  
> > > > Commit
> > > >   10efd7e108 "pc: acpi: fix memory hotplug regression by reducing stub SRAT entry size"
> > > > attemped to fix hotplug regression introduced by
> > > >   848a1cc1e "hw/acpi-build: build SRAT memory affinity structures for DIMM devices"
> > > > 
> > > > fixed issue for Windows/3.0+ linux kernels, however it regressed 2.6 based
> > > > kernels (RHEL6) to the point where guest might crash at boot.
> > > > Reason is that 2.6 kernel discards SRAT table due too small last entry
> > > > which down the road leads to crashes. Hack I've tried in 10efd7e108 is also
> > > > not ACPI spec compliant according to which whole possible RAM should be
> > > > described in SRAT. Revert 10efd7e108 to fix regression for 2.6 based kernels.
> > > > 
> > > > With 10efd7e108 reverted, I've also tried splitting SRAT table statically
> > > > in different ways %/node and %/slot but Windows still fails to online
> > > > 2nd pc-dimm hot-plugged into node 0 (as described in 10efd7e108) and
> > > > sometimes even coldplugged pc-dimms where affected with static SRAT
> > > > partitioning.
> > > > The only known so far way where Windows stays happy is when we have 1
> > > > SRAT entry in the last node covering all hotplug area.
> > > > 
> > > > Revert 848a1cc1e until we come up with a way to avoid regression
> > > > on Windows with hotplug area split in several entries.
> > > > Tested this with 2.6/3.0 based kernels (RHEL6/7) and WS20[08/12/12R2/16]).
> > > > 
> > > > Signed-off-by: Igor Mammedov <imammedo@redhat.com>
> > > > ---
> > > > CC: haozhong.zhang@intel.com
> > > > CC: mst@redhat.com
> > > > CC: qemu-stable@nongnu.org
> > > > CC: ehabkost@redhat.com
> > > > CC: lersek@redhat.com
> > > > ---
> > > >  hw/i386/acpi-build.c | 73 +++++++++-------------------------------------------
> > > >  1 file changed, 12 insertions(+), 61 deletions(-)
> > > > 
> > > > diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
> > > > index e1ee8ae..1599caa 100644
> > > > --- a/hw/i386/acpi-build.c
> > > > +++ b/hw/i386/acpi-build.c
> > > > @@ -2251,64 +2251,6 @@ build_tpm2(GArray *table_data, BIOSLinker *linker, GArray *tcpalog)
> > > >  #define HOLE_640K_START  (640 * KiB)
> > > >  #define HOLE_640K_END   (1 * MiB)
> > > >  
> > > > -static void build_srat_hotpluggable_memory(GArray *table_data, uint64_t base,
> > > > -                                           uint64_t len, int default_node)
> > > > -{
> > > > -    MemoryDeviceInfoList *info_list = qmp_memory_device_list();
> > > > -    MemoryDeviceInfoList *info;
> > > > -    MemoryDeviceInfo *mi;
> > > > -    PCDIMMDeviceInfo *di;
> > > > -    uint64_t end = base + len, cur, size;
> > > > -    bool is_nvdimm;
> > > > -    AcpiSratMemoryAffinity *numamem;
> > > > -    MemoryAffinityFlags flags;
> > > > -
> > > > -    for (cur = base, info = info_list;
> > > > -         cur < end;
> > > > -         cur += size, info = info->next) {
> > > > -        numamem = acpi_data_push(table_data, sizeof *numamem);
> > > > -
> > > > -        if (!info) {
> > > > -            /*
> > > > -             * Entry is required for Windows to enable memory hotplug in OS
> > > > -             * and for Linux to enable SWIOTLB when booted with less than
> > > > -             * 4G of RAM. Windows works better if the entry sets proximity
> > > > -             * to the highest NUMA node in the machine at the end of the
> > > > -             * reserved space.
> > > > -             * Memory devices may override proximity set by this entry,
> > > > -             * providing _PXM method if necessary.
> > > > -             */
> > > > -            build_srat_memory(numamem, end - 1, 1, default_node,
> > > > -                              MEM_AFFINITY_HOTPLUGGABLE | MEM_AFFINITY_ENABLED);
> > > > -            break;
> > > > -        }
> > > > -
> > > > -        mi = info->value;
> > > > -        is_nvdimm = (mi->type == MEMORY_DEVICE_INFO_KIND_NVDIMM);
> > > > -        di = !is_nvdimm ? mi->u.dimm.data : mi->u.nvdimm.data;
> > > > -
> > > > -        if (cur < di->addr) {
> > > > -            build_srat_memory(numamem, cur, di->addr - cur, default_node,
> > > > -                              MEM_AFFINITY_HOTPLUGGABLE | MEM_AFFINITY_ENABLED);
> > > > -            numamem = acpi_data_push(table_data, sizeof *numamem);
> > > > -        }
> > > > -
> > > > -        size = di->size;
> > > > -
> > > > -        flags = MEM_AFFINITY_ENABLED;
> > > > -        if (di->hotpluggable) {
> > > > -            flags |= MEM_AFFINITY_HOTPLUGGABLE;
> > > > -        }
> > > > -        if (is_nvdimm) {
> > > > -            flags |= MEM_AFFINITY_NON_VOLATILE;
> > > > -        }
> > > > -
> > > > -        build_srat_memory(numamem, di->addr, size, di->node, flags);
> > > > -    }
> > > > -
> > > > -    qapi_free_MemoryDeviceInfoList(info_list);
> > > > -}
> > > > -
> > > >  static void
> > > >  build_srat(GArray *table_data, BIOSLinker *linker, MachineState *machine)
> > > >  {
> > > > @@ -2414,10 +2356,19 @@ build_srat(GArray *table_data, BIOSLinker *linker, MachineState *machine)
> > > >          build_srat_memory(numamem, 0, 0, 0, MEM_AFFINITY_NOFLAGS);
> > > >      }
> > > >  
> > > > +    /*
> > > > +     * Entry is required for Windows to enable memory hotplug in OS
> > > > +     * and for Linux to enable SWIOTLB when booted with less than
> > > > +     * 4G of RAM. Windows works better if the entry sets proximity
> > > > +     * to the highest NUMA node in the machine.
> > > > +     * Memory devices may override proximity set by this entry,
> > > > +     * providing _PXM method if necessary.
> > > > +     */
> > > >      if (hotplugabble_address_space_size) {
> > > > -        build_srat_hotpluggable_memory(table_data, machine->device_memory->base,
> > > > -                                       hotplugabble_address_space_size,
> > > > -                                       pcms->numa_nodes - 1);
> > > > +        numamem = acpi_data_push(table_data, sizeof *numamem);
> > > > +        build_srat_memory(numamem, machine->device_memory->base,
> > > > +                          hotplugabble_address_space_size, pcms->numa_nodes - 1,
> > > > +                          MEM_AFFINITY_HOTPLUGGABLE | MEM_AFFINITY_ENABLED);
> > > >      }
> > > >  
> > > >      build_header(linker, table_data,
> > > >     
> > > 
> > > So this reverts both 10efd7e108 (which only moved the regression around)
> > > and the earlier 848a1cc1e (which had introduced the regression in the
> > > first place).
> > > 
> > > If I understand correctly, the issue that 848a1cc1e was meant to solve
> > > was that "-device nvdimm,node=..." could be passed by the user such that
> > > it lead to "proximity domain mismatch". (What was the higher-level goal
> > > with that BTW?)
> > > 
> > > However, that mismatch could as well be avoided by simply not passing
> > > such "node=..." properties. Is that right?
> > >
> > > If so, should we perhaps add another patch (temporarily), beyond this
> > > revert, that identifies the misconfig in question, and prints a warning
> > > about it?  
> > not exactly, before the patch node=... influenced only _PXM which is supposed
> > to be evaluated after SRAT table and override whatever was in static table.
> > 
> > The patch, as I understood it, was about ACPI spec compliance where nvdimm SPA
> > in NFIT table should have a corresponding entry in SRAT table with
> > MEM_AFFINITY_NON_VOLATILE flag set.
> > Whether it solves any real issues aren't known to me and typically for
> > Intel contributed patches, author's email doesn't exists anymore so ...
> > And even if it fixes some new nvdimm issue, I'd rather have it broken
> > than regress memory hotplug that worked fine so far and wait for another
> > nvdimm patch that won't break existing features.
> >   
> > > Anyway the revert seems justified to me.  
> > I've killed quite enough time trying to find out a way to keep
> > everyone happy, but alas it's time to give up and let interested
> > party to deal with regressions while introducing new stuff for
> > nvdimm, hence this revert.  
> 
> If the original author isn't available, I agree the best option
> is to revert it to avoid the regression by now.
> 
> Reviewed-by: Eduardo Habkost <ehabkost@redhat.com>
> 
> However, have you considered keeping adding separate entries for
> NVDIMM devices only (so we follow the spec), but add a single
> (numa_nodes-1, MEM_AFFINITY_HOTPLUGGABLE|MEM_AFFINITY_ENABLED)
> entry to the rest?
Indeed, I did. It doesn't work either.

> This way both use cases should still work as expected.  If
> Windows break if using NVDIMM + Memory Hotplug at the same time,
> maybe that's just a Windows bug we can't work around.
>

On 8/23/2018 2:01 AM, Eduardo Habkost wrote:
> On Wed, Aug 22, 2018 at 03:05:36PM +0200, Igor Mammedov wrote:
>> On Wed, 22 Aug 2018 12:06:26 +0200
>> Laszlo Ersek <lersek@redhat.com> wrote:
>>
>>> On 08/22/18 11:46, Igor Mammedov wrote:
>>>> Commit
>>>>    10efd7e108 "pc: acpi: fix memory hotplug regression by reducing stub SRAT entry size"
>>>> attemped to fix hotplug regression introduced by
>>>>    848a1cc1e "hw/acpi-build: build SRAT memory affinity structures for DIMM devices"
>>>>
>>>> fixed issue for Windows/3.0+ linux kernels, however it regressed 2.6 based
>>>> kernels (RHEL6) to the point where guest might crash at boot.
>>>> Reason is that 2.6 kernel discards SRAT table due too small last entry
>>>> which down the road leads to crashes. Hack I've tried in 10efd7e108 is also
>>>> not ACPI spec compliant according to which whole possible RAM should be
>>>> described in SRAT. Revert 10efd7e108 to fix regression for 2.6 based kernels.
>>>>
>>>> With 10efd7e108 reverted, I've also tried splitting SRAT table statically
>>>> in different ways %/node and %/slot but Windows still fails to online
>>>> 2nd pc-dimm hot-plugged into node 0 (as described in 10efd7e108) and
>>>> sometimes even coldplugged pc-dimms where affected with static SRAT
>>>> partitioning.
>>>> The only known so far way where Windows stays happy is when we have 1
>>>> SRAT entry in the last node covering all hotplug area.
>>>>
>>>> Revert 848a1cc1e until we come up with a way to avoid regression
>>>> on Windows with hotplug area split in several entries.
>>>> Tested this with 2.6/3.0 based kernels (RHEL6/7) and WS20[08/12/12R2/16]).
>>>>
>>>> Signed-off-by: Igor Mammedov <imammedo@redhat.com>
>>>> ---
>>>> CC: haozhong.zhang@intel.com
>>>> CC: mst@redhat.com
>>>> CC: qemu-stable@nongnu.org
>>>> CC: ehabkost@redhat.com
>>>> CC: lersek@redhat.com
>>>> ---
>>>>   hw/i386/acpi-build.c | 73 +++++++++-------------------------------------------
>>>>   1 file changed, 12 insertions(+), 61 deletions(-)
>>>>
>>>> diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
>>>> index e1ee8ae..1599caa 100644
>>>> --- a/hw/i386/acpi-build.c
>>>> +++ b/hw/i386/acpi-build.c
>>>> @@ -2251,64 +2251,6 @@ build_tpm2(GArray *table_data, BIOSLinker *linker, GArray *tcpalog)
>>>>   #define HOLE_640K_START  (640 * KiB)
>>>>   #define HOLE_640K_END   (1 * MiB)
>>>>   
>>>> -static void build_srat_hotpluggable_memory(GArray *table_data, uint64_t base,
>>>> -                                           uint64_t len, int default_node)
>>>> -{
>>>> -    MemoryDeviceInfoList *info_list = qmp_memory_device_list();
>>>> -    MemoryDeviceInfoList *info;
>>>> -    MemoryDeviceInfo *mi;
>>>> -    PCDIMMDeviceInfo *di;
>>>> -    uint64_t end = base + len, cur, size;
>>>> -    bool is_nvdimm;
>>>> -    AcpiSratMemoryAffinity *numamem;
>>>> -    MemoryAffinityFlags flags;
>>>> -
>>>> -    for (cur = base, info = info_list;
>>>> -         cur < end;
>>>> -         cur += size, info = info->next) {
>>>> -        numamem = acpi_data_push(table_data, sizeof *numamem);
>>>> -
>>>> -        if (!info) {
>>>> -            /*
>>>> -             * Entry is required for Windows to enable memory hotplug in OS
>>>> -             * and for Linux to enable SWIOTLB when booted with less than
>>>> -             * 4G of RAM. Windows works better if the entry sets proximity
>>>> -             * to the highest NUMA node in the machine at the end of the
>>>> -             * reserved space.
>>>> -             * Memory devices may override proximity set by this entry,
>>>> -             * providing _PXM method if necessary.
>>>> -             */
>>>> -            build_srat_memory(numamem, end - 1, 1, default_node,
>>>> -                              MEM_AFFINITY_HOTPLUGGABLE | MEM_AFFINITY_ENABLED);
>>>> -            break;
>>>> -        }
>>>> -
>>>> -        mi = info->value;
>>>> -        is_nvdimm = (mi->type == MEMORY_DEVICE_INFO_KIND_NVDIMM);
>>>> -        di = !is_nvdimm ? mi->u.dimm.data : mi->u.nvdimm.data;
>>>> -
>>>> -        if (cur < di->addr) {
>>>> -            build_srat_memory(numamem, cur, di->addr - cur, default_node,
>>>> -                              MEM_AFFINITY_HOTPLUGGABLE | MEM_AFFINITY_ENABLED);
>>>> -            numamem = acpi_data_push(table_data, sizeof *numamem);
>>>> -        }
>>>> -
>>>> -        size = di->size;
>>>> -
>>>> -        flags = MEM_AFFINITY_ENABLED;
>>>> -        if (di->hotpluggable) {
>>>> -            flags |= MEM_AFFINITY_HOTPLUGGABLE;
>>>> -        }
>>>> -        if (is_nvdimm) {
>>>> -            flags |= MEM_AFFINITY_NON_VOLATILE;
>>>> -        }
>>>> -
>>>> -        build_srat_memory(numamem, di->addr, size, di->node, flags);
>>>> -    }
>>>> -
>>>> -    qapi_free_MemoryDeviceInfoList(info_list);
>>>> -}
>>>> -
>>>>   static void
>>>>   build_srat(GArray *table_data, BIOSLinker *linker, MachineState *machine)
>>>>   {
>>>> @@ -2414,10 +2356,19 @@ build_srat(GArray *table_data, BIOSLinker *linker, MachineState *machine)
>>>>           build_srat_memory(numamem, 0, 0, 0, MEM_AFFINITY_NOFLAGS);
>>>>       }
>>>>   
>>>> +    /*
>>>> +     * Entry is required for Windows to enable memory hotplug in OS
>>>> +     * and for Linux to enable SWIOTLB when booted with less than
>>>> +     * 4G of RAM. Windows works better if the entry sets proximity
>>>> +     * to the highest NUMA node in the machine.
>>>> +     * Memory devices may override proximity set by this entry,
>>>> +     * providing _PXM method if necessary.
>>>> +     */
>>>>       if (hotplugabble_address_space_size) {
>>>> -        build_srat_hotpluggable_memory(table_data, machine->device_memory->base,
>>>> -                                       hotplugabble_address_space_size,
>>>> -                                       pcms->numa_nodes - 1);
>>>> +        numamem = acpi_data_push(table_data, sizeof *numamem);
>>>> +        build_srat_memory(numamem, machine->device_memory->base,
>>>> +                          hotplugabble_address_space_size, pcms->numa_nodes - 1,
>>>> +                          MEM_AFFINITY_HOTPLUGGABLE | MEM_AFFINITY_ENABLED);
>>>>       }
>>>>   
>>>>       build_header(linker, table_data,
>>>>    
>>> So this reverts both 10efd7e108 (which only moved the regression around)
>>> and the earlier 848a1cc1e (which had introduced the regression in the
>>> first place).
>>>
>>> If I understand correctly, the issue that 848a1cc1e was meant to solve
>>> was that "-device nvdimm,node=..." could be passed by the user such that
>>> it lead to "proximity domain mismatch". (What was the higher-level goal
>>> with that BTW?)
>>>
>>> However, that mismatch could as well be avoided by simply not passing
>>> such "node=..." properties. Is that right?
>>>
>>> If so, should we perhaps add another patch (temporarily), beyond this
>>> revert, that identifies the misconfig in question, and prints a warning
>>> about it?
>> not exactly, before the patch node=... influenced only _PXM which is supposed
>> to be evaluated after SRAT table and override whatever was in static table.
>>
>> The patch, as I understood it, was about ACPI spec compliance where nvdimm SPA
>> in NFIT table should have a corresponding entry in SRAT table with
>> MEM_AFFINITY_NON_VOLATILE flag set.
>> Whether it solves any real issues aren't known to me and typically for
>> Intel contributed patches, author's email doesn't exists anymore so ...
>> And even if it fixes some new nvdimm issue, I'd rather have it broken
>> than regress memory hotplug that worked fine so far and wait for another
>> nvdimm patch that won't break existing features.
>>
>>> Anyway the revert seems justified to me.
>> I've killed quite enough time trying to find out a way to keep
>> everyone happy, but alas it's time to give up and let interested
>> party to deal with regressions while introducing new stuff for
>> nvdimm, hence this revert.
> If the original author isn't available, I agree the best option
> is to revert it to avoid the regression by now.

Thanks Edurado, for informing us, and sorry for the delayed reply.
I'm not the author of the original patch(848a1cc1e), and is just trying 
to understand
this part now...

And my understanding is that the patch was cooked to make sure data in SRAT
align with the ones in NFIT.

> Reviewed-by: Eduardo Habkost <ehabkost@redhat.com>
>
> However, have you considered keeping adding separate entries for
> NVDIMM devices only (so we follow the spec), but add a single
> (numa_nodes-1, MEM_AFFINITY_HOTPLUGGABLE|MEM_AFFINITY_ENABLED)
> entry to the rest?

And I think that is what Igor did in patch 10efd7e108.

But I feel puzzled why windows has such requirement. And I am also 
curious, is
this a windows specific issue?

Reverting 848a1cc1e will lead the VM not able to figure out the correct 
NUMA info,
e.g. when we are trying to assign different regions from NVDIMMs 
residing on different
NUMA node.

B.R.
Yu

> This way both use cases should still work as expected.  If
> Windows break if using NVDIMM + Memory Hotplug at the same time,
> maybe that's just a Windows bug we can't work around.
>

On Thu, 23 Aug 2018 17:01:33 +0800
Yu Zhang <yu.c.zhang@linux.intel.com> wrote:

> On 8/23/2018 2:01 AM, Eduardo Habkost wrote:
> > On Wed, Aug 22, 2018 at 03:05:36PM +0200, Igor Mammedov wrote:  
> >> On Wed, 22 Aug 2018 12:06:26 +0200
> >> Laszlo Ersek <lersek@redhat.com> wrote:
> >>  
> >>> On 08/22/18 11:46, Igor Mammedov wrote:  
> >>>> Commit
> >>>>    10efd7e108 "pc: acpi: fix memory hotplug regression by reducing stub SRAT entry size"
> >>>> attemped to fix hotplug regression introduced by
> >>>>    848a1cc1e "hw/acpi-build: build SRAT memory affinity structures for DIMM devices"
> >>>>
> >>>> fixed issue for Windows/3.0+ linux kernels, however it regressed 2.6 based
> >>>> kernels (RHEL6) to the point where guest might crash at boot.
> >>>> Reason is that 2.6 kernel discards SRAT table due too small last entry
> >>>> which down the road leads to crashes. Hack I've tried in 10efd7e108 is also
> >>>> not ACPI spec compliant according to which whole possible RAM should be
> >>>> described in SRAT. Revert 10efd7e108 to fix regression for 2.6 based kernels.
> >>>>
> >>>> With 10efd7e108 reverted, I've also tried splitting SRAT table statically
> >>>> in different ways %/node and %/slot but Windows still fails to online
> >>>> 2nd pc-dimm hot-plugged into node 0 (as described in 10efd7e108) and
> >>>> sometimes even coldplugged pc-dimms where affected with static SRAT
> >>>> partitioning.
> >>>> The only known so far way where Windows stays happy is when we have 1
> >>>> SRAT entry in the last node covering all hotplug area.
> >>>>
> >>>> Revert 848a1cc1e until we come up with a way to avoid regression
> >>>> on Windows with hotplug area split in several entries.
> >>>> Tested this with 2.6/3.0 based kernels (RHEL6/7) and WS20[08/12/12R2/16]).
> >>>>
> >>>> Signed-off-by: Igor Mammedov <imammedo@redhat.com>
> >>>> ---
> >>>> CC: haozhong.zhang@intel.com
> >>>> CC: mst@redhat.com
> >>>> CC: qemu-stable@nongnu.org
> >>>> CC: ehabkost@redhat.com
> >>>> CC: lersek@redhat.com
> >>>> ---
> >>>>   hw/i386/acpi-build.c | 73 +++++++++-------------------------------------------
> >>>>   1 file changed, 12 insertions(+), 61 deletions(-)
> >>>>
> >>>> diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
> >>>> index e1ee8ae..1599caa 100644
> >>>> --- a/hw/i386/acpi-build.c
> >>>> +++ b/hw/i386/acpi-build.c
> >>>> @@ -2251,64 +2251,6 @@ build_tpm2(GArray *table_data, BIOSLinker *linker, GArray *tcpalog)
> >>>>   #define HOLE_640K_START  (640 * KiB)
> >>>>   #define HOLE_640K_END   (1 * MiB)
> >>>>   
> >>>> -static void build_srat_hotpluggable_memory(GArray *table_data, uint64_t base,
> >>>> -                                           uint64_t len, int default_node)
> >>>> -{
> >>>> -    MemoryDeviceInfoList *info_list = qmp_memory_device_list();
> >>>> -    MemoryDeviceInfoList *info;
> >>>> -    MemoryDeviceInfo *mi;
> >>>> -    PCDIMMDeviceInfo *di;
> >>>> -    uint64_t end = base + len, cur, size;
> >>>> -    bool is_nvdimm;
> >>>> -    AcpiSratMemoryAffinity *numamem;
> >>>> -    MemoryAffinityFlags flags;
> >>>> -
> >>>> -    for (cur = base, info = info_list;
> >>>> -         cur < end;
> >>>> -         cur += size, info = info->next) {
> >>>> -        numamem = acpi_data_push(table_data, sizeof *numamem);
> >>>> -
> >>>> -        if (!info) {
> >>>> -            /*
> >>>> -             * Entry is required for Windows to enable memory hotplug in OS
> >>>> -             * and for Linux to enable SWIOTLB when booted with less than
> >>>> -             * 4G of RAM. Windows works better if the entry sets proximity
> >>>> -             * to the highest NUMA node in the machine at the end of the
> >>>> -             * reserved space.
> >>>> -             * Memory devices may override proximity set by this entry,
> >>>> -             * providing _PXM method if necessary.
> >>>> -             */
> >>>> -            build_srat_memory(numamem, end - 1, 1, default_node,
> >>>> -                              MEM_AFFINITY_HOTPLUGGABLE | MEM_AFFINITY_ENABLED);
> >>>> -            break;
> >>>> -        }
> >>>> -
> >>>> -        mi = info->value;
> >>>> -        is_nvdimm = (mi->type == MEMORY_DEVICE_INFO_KIND_NVDIMM);
> >>>> -        di = !is_nvdimm ? mi->u.dimm.data : mi->u.nvdimm.data;
> >>>> -
> >>>> -        if (cur < di->addr) {
> >>>> -            build_srat_memory(numamem, cur, di->addr - cur, default_node,
> >>>> -                              MEM_AFFINITY_HOTPLUGGABLE | MEM_AFFINITY_ENABLED);
> >>>> -            numamem = acpi_data_push(table_data, sizeof *numamem);
> >>>> -        }
> >>>> -
> >>>> -        size = di->size;
> >>>> -
> >>>> -        flags = MEM_AFFINITY_ENABLED;
> >>>> -        if (di->hotpluggable) {
> >>>> -            flags |= MEM_AFFINITY_HOTPLUGGABLE;
> >>>> -        }
> >>>> -        if (is_nvdimm) {
> >>>> -            flags |= MEM_AFFINITY_NON_VOLATILE;
> >>>> -        }
> >>>> -
> >>>> -        build_srat_memory(numamem, di->addr, size, di->node, flags);
> >>>> -    }
> >>>> -
> >>>> -    qapi_free_MemoryDeviceInfoList(info_list);
> >>>> -}
> >>>> -
> >>>>   static void
> >>>>   build_srat(GArray *table_data, BIOSLinker *linker, MachineState *machine)
> >>>>   {
> >>>> @@ -2414,10 +2356,19 @@ build_srat(GArray *table_data, BIOSLinker *linker, MachineState *machine)
> >>>>           build_srat_memory(numamem, 0, 0, 0, MEM_AFFINITY_NOFLAGS);
> >>>>       }
> >>>>   
> >>>> +    /*
> >>>> +     * Entry is required for Windows to enable memory hotplug in OS
> >>>> +     * and for Linux to enable SWIOTLB when booted with less than
> >>>> +     * 4G of RAM. Windows works better if the entry sets proximity
> >>>> +     * to the highest NUMA node in the machine.
> >>>> +     * Memory devices may override proximity set by this entry,
> >>>> +     * providing _PXM method if necessary.
> >>>> +     */
> >>>>       if (hotplugabble_address_space_size) {
> >>>> -        build_srat_hotpluggable_memory(table_data, machine->device_memory->base,
> >>>> -                                       hotplugabble_address_space_size,
> >>>> -                                       pcms->numa_nodes - 1);
> >>>> +        numamem = acpi_data_push(table_data, sizeof *numamem);
> >>>> +        build_srat_memory(numamem, machine->device_memory->base,
> >>>> +                          hotplugabble_address_space_size, pcms->numa_nodes - 1,
> >>>> +                          MEM_AFFINITY_HOTPLUGGABLE | MEM_AFFINITY_ENABLED);
> >>>>       }
> >>>>   
> >>>>       build_header(linker, table_data,
> >>>>      
> >>> So this reverts both 10efd7e108 (which only moved the regression around)
> >>> and the earlier 848a1cc1e (which had introduced the regression in the
> >>> first place).
> >>>
> >>> If I understand correctly, the issue that 848a1cc1e was meant to solve
> >>> was that "-device nvdimm,node=..." could be passed by the user such that
> >>> it lead to "proximity domain mismatch". (What was the higher-level goal
> >>> with that BTW?)
> >>>
> >>> However, that mismatch could as well be avoided by simply not passing
> >>> such "node=..." properties. Is that right?
> >>>
> >>> If so, should we perhaps add another patch (temporarily), beyond this
> >>> revert, that identifies the misconfig in question, and prints a warning
> >>> about it?  
> >> not exactly, before the patch node=... influenced only _PXM which is supposed
> >> to be evaluated after SRAT table and override whatever was in static table.
> >>
> >> The patch, as I understood it, was about ACPI spec compliance where nvdimm SPA
> >> in NFIT table should have a corresponding entry in SRAT table with
> >> MEM_AFFINITY_NON_VOLATILE flag set.
> >> Whether it solves any real issues aren't known to me and typically for
> >> Intel contributed patches, author's email doesn't exists anymore so ...
> >> And even if it fixes some new nvdimm issue, I'd rather have it broken
> >> than regress memory hotplug that worked fine so far and wait for another
> >> nvdimm patch that won't break existing features.
> >>  
> >>> Anyway the revert seems justified to me.  
> >> I've killed quite enough time trying to find out a way to keep
> >> everyone happy, but alas it's time to give up and let interested
> >> party to deal with regressions while introducing new stuff for
> >> nvdimm, hence this revert.  
> > If the original author isn't available, I agree the best option
> > is to revert it to avoid the regression by now.  
> 
> Thanks Edurado, for informing us, and sorry for the delayed reply.
> I'm not the author of the original patch(848a1cc1e), and is just trying 
> to understand
> this part now...
> 
> And my understanding is that the patch was cooked to make sure data in SRAT
> align with the ones in NFIT.
> 
> > Reviewed-by: Eduardo Habkost <ehabkost@redhat.com>
> >
> > However, have you considered keeping adding separate entries for
> > NVDIMM devices only (so we follow the spec), but add a single
> > (numa_nodes-1, MEM_AFFINITY_HOTPLUGGABLE|MEM_AFFINITY_ENABLED)
> > entry to the rest?  
> 
> And I think that is what Igor did in patch 10efd7e108.
> 
> But I feel puzzled why windows has such requirement. And I am also 
> curious, is
> this a windows specific issue?
It's is a Windows issue, but QEMU doesn't differentiate between guests
OSes so in general it should work for all of them or at least do not break
existing features.


> Reverting 848a1cc1e will lead the VM not able to figure out the correct 
> NUMA info,
> e.g. when we are trying to assign different regions from NVDIMMs 
> residing on different
> NUMA node.
that's probably non issue as QEMU's impl. supports only 1:1 mapping,
i.e. SPA for whole nvdimm goes to 1 node and SPA record already
contains node ID it belongs to.

The reason why I've acked 848a1cc1e is that it's correct per ACPI spec,
but unfortunately QE found a test case where it regresses memory hotplug,
hence a revert. We should find out a way to be spec compliant and
not to break existing features.

Perhaps you'd be able to figure out how to accomplish both goals,
I'd be happy to help you out if you'd need some assistance.


> 
> B.R.
> Yu
> 
> > This way both use cases should still work as expected.  If
> > Windows break if using NVDIMM + Memory Hotplug at the same time,
> > maybe that's just a Windows bug we can't work around.
> >

On Thu, Aug 23, 2018 at 10:14:06AM +0200, Igor Mammedov wrote:
> On Wed, 22 Aug 2018 15:01:12 -0300
> Eduardo Habkost <ehabkost@redhat.com> wrote:
[...]
> > However, have you considered keeping adding separate entries for
> > NVDIMM devices only (so we follow the spec), but add a single
> > (numa_nodes-1, MEM_AFFINITY_HOTPLUGGABLE|MEM_AFFINITY_ENABLED)
> > entry to the rest?
> Indeed, I did. It doesn't work either.

When exactly it didn't work?  Did nvdimm + memory hotplug ever
worked together on Windows guests?

For all the other cases there should be absolutely no difference:

nvdimm users would still get a spec-compliant SRAT table (like on
QEMU 3.0).

Memory hotplug users w/o nvdimm would get the same ACPI table
that they would get after applying this patch (i.e. the one we
had before commit 848a1cc1e ("hw/acpi-build: build SRAT memory
affinity structures for DIMM devices").

On Thu, Aug 23, 2018 at 02:34:31PM +0200, Igor Mammedov wrote:
> On Thu, 23 Aug 2018 17:01:33 +0800
> Yu Zhang <yu.c.zhang@linux.intel.com> wrote:
> 
> > On 8/23/2018 2:01 AM, Eduardo Habkost wrote:
> > > On Wed, Aug 22, 2018 at 03:05:36PM +0200, Igor Mammedov wrote:  
> > >> On Wed, 22 Aug 2018 12:06:26 +0200
> > >> Laszlo Ersek <lersek@redhat.com> wrote:
> > >>  
> > >>> On 08/22/18 11:46, Igor Mammedov wrote:  
> > >>>> Commit
> > >>>>    10efd7e108 "pc: acpi: fix memory hotplug regression by reducing stub SRAT entry size"
> > >>>> attemped to fix hotplug regression introduced by
> > >>>>    848a1cc1e "hw/acpi-build: build SRAT memory affinity structures for DIMM devices"
> > >>>>
> > >>>> fixed issue for Windows/3.0+ linux kernels, however it regressed 2.6 based
> > >>>> kernels (RHEL6) to the point where guest might crash at boot.
> > >>>> Reason is that 2.6 kernel discards SRAT table due too small last entry
> > >>>> which down the road leads to crashes. Hack I've tried in 10efd7e108 is also
> > >>>> not ACPI spec compliant according to which whole possible RAM should be
> > >>>> described in SRAT. Revert 10efd7e108 to fix regression for 2.6 based kernels.
> > >>>>
> > >>>> With 10efd7e108 reverted, I've also tried splitting SRAT table statically
> > >>>> in different ways %/node and %/slot but Windows still fails to online
> > >>>> 2nd pc-dimm hot-plugged into node 0 (as described in 10efd7e108) and
> > >>>> sometimes even coldplugged pc-dimms where affected with static SRAT
> > >>>> partitioning.
> > >>>> The only known so far way where Windows stays happy is when we have 1
> > >>>> SRAT entry in the last node covering all hotplug area.
> > >>>>
> > >>>> Revert 848a1cc1e until we come up with a way to avoid regression
> > >>>> on Windows with hotplug area split in several entries.
> > >>>> Tested this with 2.6/3.0 based kernels (RHEL6/7) and WS20[08/12/12R2/16]).
> > >>>>
> > >>>> Signed-off-by: Igor Mammedov <imammedo@redhat.com>
> > >>>> ---
> > >>>> CC: haozhong.zhang@intel.com
> > >>>> CC: mst@redhat.com
> > >>>> CC: qemu-stable@nongnu.org
> > >>>> CC: ehabkost@redhat.com
> > >>>> CC: lersek@redhat.com
> > >>>> ---
> > >>>>   hw/i386/acpi-build.c | 73 +++++++++-------------------------------------------
> > >>>>   1 file changed, 12 insertions(+), 61 deletions(-)
> > >>>>
> > >>>> diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
> > >>>> index e1ee8ae..1599caa 100644
> > >>>> --- a/hw/i386/acpi-build.c
> > >>>> +++ b/hw/i386/acpi-build.c
> > >>>> @@ -2251,64 +2251,6 @@ build_tpm2(GArray *table_data, BIOSLinker *linker, GArray *tcpalog)
> > >>>>   #define HOLE_640K_START  (640 * KiB)
> > >>>>   #define HOLE_640K_END   (1 * MiB)
> > >>>>   
> > >>>> -static void build_srat_hotpluggable_memory(GArray *table_data, uint64_t base,
> > >>>> -                                           uint64_t len, int default_node)
> > >>>> -{
> > >>>> -    MemoryDeviceInfoList *info_list = qmp_memory_device_list();
> > >>>> -    MemoryDeviceInfoList *info;
> > >>>> -    MemoryDeviceInfo *mi;
> > >>>> -    PCDIMMDeviceInfo *di;
> > >>>> -    uint64_t end = base + len, cur, size;
> > >>>> -    bool is_nvdimm;
> > >>>> -    AcpiSratMemoryAffinity *numamem;
> > >>>> -    MemoryAffinityFlags flags;
> > >>>> -
> > >>>> -    for (cur = base, info = info_list;
> > >>>> -         cur < end;
> > >>>> -         cur += size, info = info->next) {
> > >>>> -        numamem = acpi_data_push(table_data, sizeof *numamem);
> > >>>> -
> > >>>> -        if (!info) {
> > >>>> -            /*
> > >>>> -             * Entry is required for Windows to enable memory hotplug in OS
> > >>>> -             * and for Linux to enable SWIOTLB when booted with less than
> > >>>> -             * 4G of RAM. Windows works better if the entry sets proximity
> > >>>> -             * to the highest NUMA node in the machine at the end of the
> > >>>> -             * reserved space.
> > >>>> -             * Memory devices may override proximity set by this entry,
> > >>>> -             * providing _PXM method if necessary.
> > >>>> -             */
> > >>>> -            build_srat_memory(numamem, end - 1, 1, default_node,
> > >>>> -                              MEM_AFFINITY_HOTPLUGGABLE | MEM_AFFINITY_ENABLED);
> > >>>> -            break;
> > >>>> -        }
> > >>>> -
> > >>>> -        mi = info->value;
> > >>>> -        is_nvdimm = (mi->type == MEMORY_DEVICE_INFO_KIND_NVDIMM);
> > >>>> -        di = !is_nvdimm ? mi->u.dimm.data : mi->u.nvdimm.data;
> > >>>> -
> > >>>> -        if (cur < di->addr) {
> > >>>> -            build_srat_memory(numamem, cur, di->addr - cur, default_node,
> > >>>> -                              MEM_AFFINITY_HOTPLUGGABLE | MEM_AFFINITY_ENABLED);
> > >>>> -            numamem = acpi_data_push(table_data, sizeof *numamem);
> > >>>> -        }
> > >>>> -
> > >>>> -        size = di->size;
> > >>>> -
> > >>>> -        flags = MEM_AFFINITY_ENABLED;
> > >>>> -        if (di->hotpluggable) {
> > >>>> -            flags |= MEM_AFFINITY_HOTPLUGGABLE;
> > >>>> -        }
> > >>>> -        if (is_nvdimm) {
> > >>>> -            flags |= MEM_AFFINITY_NON_VOLATILE;
> > >>>> -        }
> > >>>> -
> > >>>> -        build_srat_memory(numamem, di->addr, size, di->node, flags);
> > >>>> -    }
> > >>>> -
> > >>>> -    qapi_free_MemoryDeviceInfoList(info_list);
> > >>>> -}
> > >>>> -
> > >>>>   static void
> > >>>>   build_srat(GArray *table_data, BIOSLinker *linker, MachineState *machine)
> > >>>>   {
> > >>>> @@ -2414,10 +2356,19 @@ build_srat(GArray *table_data, BIOSLinker *linker, MachineState *machine)
> > >>>>           build_srat_memory(numamem, 0, 0, 0, MEM_AFFINITY_NOFLAGS);
> > >>>>       }
> > >>>>   
> > >>>> +    /*
> > >>>> +     * Entry is required for Windows to enable memory hotplug in OS
> > >>>> +     * and for Linux to enable SWIOTLB when booted with less than
> > >>>> +     * 4G of RAM. Windows works better if the entry sets proximity
> > >>>> +     * to the highest NUMA node in the machine.
> > >>>> +     * Memory devices may override proximity set by this entry,
> > >>>> +     * providing _PXM method if necessary.
> > >>>> +     */
> > >>>>       if (hotplugabble_address_space_size) {
> > >>>> -        build_srat_hotpluggable_memory(table_data, machine->device_memory->base,
> > >>>> -                                       hotplugabble_address_space_size,
> > >>>> -                                       pcms->numa_nodes - 1);
> > >>>> +        numamem = acpi_data_push(table_data, sizeof *numamem);
> > >>>> +        build_srat_memory(numamem, machine->device_memory->base,
> > >>>> +                          hotplugabble_address_space_size, pcms->numa_nodes - 1,
> > >>>> +                          MEM_AFFINITY_HOTPLUGGABLE | MEM_AFFINITY_ENABLED);
> > >>>>       }
> > >>>>   
> > >>>>       build_header(linker, table_data,
> > >>>>      
> > >>> So this reverts both 10efd7e108 (which only moved the regression around)
> > >>> and the earlier 848a1cc1e (which had introduced the regression in the
> > >>> first place).
> > >>>
> > >>> If I understand correctly, the issue that 848a1cc1e was meant to solve
> > >>> was that "-device nvdimm,node=..." could be passed by the user such that
> > >>> it lead to "proximity domain mismatch". (What was the higher-level goal
> > >>> with that BTW?)
> > >>>
> > >>> However, that mismatch could as well be avoided by simply not passing
> > >>> such "node=..." properties. Is that right?
> > >>>
> > >>> If so, should we perhaps add another patch (temporarily), beyond this
> > >>> revert, that identifies the misconfig in question, and prints a warning
> > >>> about it?  
> > >> not exactly, before the patch node=... influenced only _PXM which is supposed
> > >> to be evaluated after SRAT table and override whatever was in static table.
> > >>
> > >> The patch, as I understood it, was about ACPI spec compliance where nvdimm SPA
> > >> in NFIT table should have a corresponding entry in SRAT table with
> > >> MEM_AFFINITY_NON_VOLATILE flag set.
> > >> Whether it solves any real issues aren't known to me and typically for
> > >> Intel contributed patches, author's email doesn't exists anymore so ...
> > >> And even if it fixes some new nvdimm issue, I'd rather have it broken
> > >> than regress memory hotplug that worked fine so far and wait for another
> > >> nvdimm patch that won't break existing features.
> > >>  
> > >>> Anyway the revert seems justified to me.  
> > >> I've killed quite enough time trying to find out a way to keep
> > >> everyone happy, but alas it's time to give up and let interested
> > >> party to deal with regressions while introducing new stuff for
> > >> nvdimm, hence this revert.  
> > > If the original author isn't available, I agree the best option
> > > is to revert it to avoid the regression by now.  
> > 
> > Thanks Edurado, for informing us, and sorry for the delayed reply.
> > I'm not the author of the original patch(848a1cc1e), and is just trying 
> > to understand
> > this part now...
> > 
> > And my understanding is that the patch was cooked to make sure data in SRAT
> > align with the ones in NFIT.
> > 
> > > Reviewed-by: Eduardo Habkost <ehabkost@redhat.com>
> > >
> > > However, have you considered keeping adding separate entries for
> > > NVDIMM devices only (so we follow the spec), but add a single
> > > (numa_nodes-1, MEM_AFFINITY_HOTPLUGGABLE|MEM_AFFINITY_ENABLED)
> > > entry to the rest?  
> > 
> > And I think that is what Igor did in patch 10efd7e108.
> > 
> > But I feel puzzled why windows has such requirement. And I am also 
> > curious, is
> > this a windows specific issue?
> It's is a Windows issue, but QEMU doesn't differentiate between guests
> OSes so in general it should work for all of them or at least do not break
> existing features.
> 

Yes, agreed.

> 
> > Reverting 848a1cc1e will lead the VM not able to figure out the correct 
> > NUMA info,
> > e.g. when we are trying to assign different regions from NVDIMMs 
> > residing on different
> > NUMA node.
> that's probably non issue as QEMU's impl. supports only 1:1 mapping,
> i.e. SPA for whole nvdimm goes to 1 node and SPA record already
> contains node ID it belongs to.
> 
> The reason why I've acked 848a1cc1e is that it's correct per ACPI spec,
> but unfortunately QE found a test case where it regresses memory hotplug,
> hence a revert. We should find out a way to be spec compliant and
> not to break existing features.
> 

I agree it's not easy to match all the requirements. So let's revert this
first. :)

B.R.
Yu

> Perhaps you'd be able to figure out how to accomplish both goals,
> I'd be happy to help you out if you'd need some assistance.
> 
> 
> > 
> > B.R.
> > Yu
> > 
> > > This way both use cases should still work as expected.  If
> > > Windows break if using NVDIMM + Memory Hotplug at the same time,
> > > maybe that's just a Windows bug we can't work around.
> > >  
> 
>

On Thu, 23 Aug 2018 14:25:01 -0300
Eduardo Habkost <ehabkost@redhat.com> wrote:

> On Thu, Aug 23, 2018 at 10:14:06AM +0200, Igor Mammedov wrote:
> > On Wed, 22 Aug 2018 15:01:12 -0300
> > Eduardo Habkost <ehabkost@redhat.com> wrote:  
> [...]
> > > However, have you considered keeping adding separate entries for
> > > NVDIMM devices only (so we follow the spec), but add a single
> > > (numa_nodes-1, MEM_AFFINITY_HOTPLUGGABLE|MEM_AFFINITY_ENABLED)
> > > entry to the rest?  
> > Indeed, I did. It doesn't work either.  
> 
> When exactly it didn't work?  Did nvdimm + memory hotplug ever
> worked together on Windows guests?
before 848a1cc1e QEMU CLI with nvdimm + memory hotplug worked
as expected for Windows.
With approach you suggested, it would create several SRAT entries
X for nvdimm and Y for the rest (1 in the best case or many if
nvdimms/pc-dimms are interleaved) and that breaks memory hotplug.
 
> For all the other cases there should be absolutely no difference:
> 
> nvdimm users would still get a spec-compliant SRAT table (like on
> QEMU 3.0).
> 
> Memory hotplug users w/o nvdimm would get the same ACPI table
> that they would get after applying this patch (i.e. the one we
> had before commit 848a1cc1e ("hw/acpi-build: build SRAT memory
> affinity structures for DIMM devices").
I did consider it. It still would be a regression but a minor one
(only Windows nvdimm enabled cases will have regressed memory
hotplug). I even have a patch for it, but it's still a regression,
that's why I've posted full 848a1cc1e revert.

If it were a bug in the newest version of windows (assuming it's
proven Windows bug), I'd be inclined towards being spec compliant
and let MS fix Windows as it was with CPU hotplug (hijacked ACPI0010
container) which they eventually fixed, but in this case it affects
all guests versions and there is no proof that's a Windows bug.

So my hope here is that Intel has resources to figure out what
Windows expectations are wrt SRAT/memory layout and memory hotplug.

On Fri, Aug 24, 2018 at 10:03:05AM +0200, Igor Mammedov wrote:
> On Thu, 23 Aug 2018 14:25:01 -0300
> Eduardo Habkost <ehabkost@redhat.com> wrote:
> 
> > On Thu, Aug 23, 2018 at 10:14:06AM +0200, Igor Mammedov wrote:
> > > On Wed, 22 Aug 2018 15:01:12 -0300
> > > Eduardo Habkost <ehabkost@redhat.com> wrote:  
> > [...]
> > > > However, have you considered keeping adding separate entries for
> > > > NVDIMM devices only (so we follow the spec), but add a single
> > > > (numa_nodes-1, MEM_AFFINITY_HOTPLUGGABLE|MEM_AFFINITY_ENABLED)
> > > > entry to the rest?  
> > > Indeed, I did. It doesn't work either.  
> > 
> > When exactly it didn't work?  Did nvdimm + memory hotplug ever
> > worked together on Windows guests?
> before 848a1cc1e QEMU CLI with nvdimm + memory hotplug worked
> as expected for Windows.

OK, so my suggestion would still have a regression.  Nevermind.

> With approach you suggested, it would create several SRAT entries
> X for nvdimm and Y for the rest (1 in the best case or many if
> nvdimms/pc-dimms are interleaved) and that breaks memory hotplug.
>  
> > For all the other cases there should be absolutely no difference:
> > 
> > nvdimm users would still get a spec-compliant SRAT table (like on
> > QEMU 3.0).
> > 
> > Memory hotplug users w/o nvdimm would get the same ACPI table
> > that they would get after applying this patch (i.e. the one we
> > had before commit 848a1cc1e ("hw/acpi-build: build SRAT memory
> > affinity structures for DIMM devices").
> I did consider it. It still would be a regression but a minor one
> (only Windows nvdimm enabled cases will have regressed memory
> hotplug). I even have a patch for it, but it's still a regression,
> that's why I've posted full 848a1cc1e revert.
> 
> If it were a bug in the newest version of windows (assuming it's
> proven Windows bug), I'd be inclined towards being spec compliant
> and let MS fix Windows as it was with CPU hotplug (hijacked ACPI0010
> container) which they eventually fixed, but in this case it affects
> all guests versions and there is no proof that's a Windows bug.
> 
> So my hope here is that Intel has resources to figure out what
> Windows expectations are wrt SRAT/memory layout and memory hotplug.

Agreed.

On Wed, Aug 22, 2018 at 11:46:44AM +0200, Igor Mammedov wrote:
> Commit
>   10efd7e108 "pc: acpi: fix memory hotplug regression by reducing stub SRAT entry size"
> attemped to fix hotplug regression introduced by
>   848a1cc1e "hw/acpi-build: build SRAT memory affinity structures for DIMM devices"
> 
> fixed issue for Windows/3.0+ linux kernels, however it regressed 2.6 based
> kernels (RHEL6) to the point where guest might crash at boot.
> Reason is that 2.6 kernel discards SRAT table due too small last entry
> which down the road leads to crashes. Hack I've tried in 10efd7e108 is also
> not ACPI spec compliant according to which whole possible RAM should be
> described in SRAT. Revert 10efd7e108 to fix regression for 2.6 based kernels.
> 
> With 10efd7e108 reverted, I've also tried splitting SRAT table statically
> in different ways %/node and %/slot but Windows still fails to online
> 2nd pc-dimm hot-plugged into node 0 (as described in 10efd7e108) and
> sometimes even coldplugged pc-dimms where affected with static SRAT
> partitioning.
> The only known so far way where Windows stays happy is when we have 1
> SRAT entry in the last node covering all hotplug area.
> 
> Revert 848a1cc1e until we come up with a way to avoid regression
> on Windows with hotplug area split in several entries.
> Tested this with 2.6/3.0 based kernels (RHEL6/7) and WS20[08/12/12R2/16]).
> 
> Signed-off-by: Igor Mammedov <imammedo@redhat.com>

BTW should this cause any aml test blobs to change?
Does not seem to ...

> ---
> CC: haozhong.zhang@intel.com
> CC: mst@redhat.com
> CC: qemu-stable@nongnu.org
> CC: ehabkost@redhat.com
> CC: lersek@redhat.com
> ---
>  hw/i386/acpi-build.c | 73 +++++++++-------------------------------------------
>  1 file changed, 12 insertions(+), 61 deletions(-)
> 
> diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
> index e1ee8ae..1599caa 100644
> --- a/hw/i386/acpi-build.c
> +++ b/hw/i386/acpi-build.c
> @@ -2251,64 +2251,6 @@ build_tpm2(GArray *table_data, BIOSLinker *linker, GArray *tcpalog)
>  #define HOLE_640K_START  (640 * KiB)
>  #define HOLE_640K_END   (1 * MiB)
>  
> -static void build_srat_hotpluggable_memory(GArray *table_data, uint64_t base,
> -                                           uint64_t len, int default_node)
> -{
> -    MemoryDeviceInfoList *info_list = qmp_memory_device_list();
> -    MemoryDeviceInfoList *info;
> -    MemoryDeviceInfo *mi;
> -    PCDIMMDeviceInfo *di;
> -    uint64_t end = base + len, cur, size;
> -    bool is_nvdimm;
> -    AcpiSratMemoryAffinity *numamem;
> -    MemoryAffinityFlags flags;
> -
> -    for (cur = base, info = info_list;
> -         cur < end;
> -         cur += size, info = info->next) {
> -        numamem = acpi_data_push(table_data, sizeof *numamem);
> -
> -        if (!info) {
> -            /*
> -             * Entry is required for Windows to enable memory hotplug in OS
> -             * and for Linux to enable SWIOTLB when booted with less than
> -             * 4G of RAM. Windows works better if the entry sets proximity
> -             * to the highest NUMA node in the machine at the end of the
> -             * reserved space.
> -             * Memory devices may override proximity set by this entry,
> -             * providing _PXM method if necessary.
> -             */
> -            build_srat_memory(numamem, end - 1, 1, default_node,
> -                              MEM_AFFINITY_HOTPLUGGABLE | MEM_AFFINITY_ENABLED);
> -            break;
> -        }
> -
> -        mi = info->value;
> -        is_nvdimm = (mi->type == MEMORY_DEVICE_INFO_KIND_NVDIMM);
> -        di = !is_nvdimm ? mi->u.dimm.data : mi->u.nvdimm.data;
> -
> -        if (cur < di->addr) {
> -            build_srat_memory(numamem, cur, di->addr - cur, default_node,
> -                              MEM_AFFINITY_HOTPLUGGABLE | MEM_AFFINITY_ENABLED);
> -            numamem = acpi_data_push(table_data, sizeof *numamem);
> -        }
> -
> -        size = di->size;
> -
> -        flags = MEM_AFFINITY_ENABLED;
> -        if (di->hotpluggable) {
> -            flags |= MEM_AFFINITY_HOTPLUGGABLE;
> -        }
> -        if (is_nvdimm) {
> -            flags |= MEM_AFFINITY_NON_VOLATILE;
> -        }
> -
> -        build_srat_memory(numamem, di->addr, size, di->node, flags);
> -    }
> -
> -    qapi_free_MemoryDeviceInfoList(info_list);
> -}
> -
>  static void
>  build_srat(GArray *table_data, BIOSLinker *linker, MachineState *machine)
>  {
> @@ -2414,10 +2356,19 @@ build_srat(GArray *table_data, BIOSLinker *linker, MachineState *machine)
>          build_srat_memory(numamem, 0, 0, 0, MEM_AFFINITY_NOFLAGS);
>      }
>  
> +    /*
> +     * Entry is required for Windows to enable memory hotplug in OS
> +     * and for Linux to enable SWIOTLB when booted with less than
> +     * 4G of RAM. Windows works better if the entry sets proximity
> +     * to the highest NUMA node in the machine.
> +     * Memory devices may override proximity set by this entry,
> +     * providing _PXM method if necessary.
> +     */
>      if (hotplugabble_address_space_size) {
> -        build_srat_hotpluggable_memory(table_data, machine->device_memory->base,
> -                                       hotplugabble_address_space_size,
> -                                       pcms->numa_nodes - 1);
> +        numamem = acpi_data_push(table_data, sizeof *numamem);
> +        build_srat_memory(numamem, machine->device_memory->base,
> +                          hotplugabble_address_space_size, pcms->numa_nodes - 1,
> +                          MEM_AFFINITY_HOTPLUGGABLE | MEM_AFFINITY_ENABLED);
>      }
>  
>      build_header(linker, table_data,
> -- 
> 2.7.4

On Fri, 7 Sep 2018 16:44:34 -0400
"Michael S. Tsirkin" <mst@redhat.com> wrote:

> On Wed, Aug 22, 2018 at 11:46:44AM +0200, Igor Mammedov wrote:
> > Commit
> >   10efd7e108 "pc: acpi: fix memory hotplug regression by reducing stub SRAT entry size"
> > attemped to fix hotplug regression introduced by
> >   848a1cc1e "hw/acpi-build: build SRAT memory affinity structures for DIMM devices"
> > 
> > fixed issue for Windows/3.0+ linux kernels, however it regressed 2.6 based
> > kernels (RHEL6) to the point where guest might crash at boot.
> > Reason is that 2.6 kernel discards SRAT table due too small last entry
> > which down the road leads to crashes. Hack I've tried in 10efd7e108 is also
> > not ACPI spec compliant according to which whole possible RAM should be
> > described in SRAT. Revert 10efd7e108 to fix regression for 2.6 based kernels.
> > 
> > With 10efd7e108 reverted, I've also tried splitting SRAT table statically
> > in different ways %/node and %/slot but Windows still fails to online
> > 2nd pc-dimm hot-plugged into node 0 (as described in 10efd7e108) and
> > sometimes even coldplugged pc-dimms where affected with static SRAT
> > partitioning.
> > The only known so far way where Windows stays happy is when we have 1
> > SRAT entry in the last node covering all hotplug area.
> > 
> > Revert 848a1cc1e until we come up with a way to avoid regression
> > on Windows with hotplug area split in several entries.
> > Tested this with 2.6/3.0 based kernels (RHEL6/7) and WS20[08/12/12R2/16]).
> > 
> > Signed-off-by: Igor Mammedov <imammedo@redhat.com>  
> 
> BTW should this cause any aml test blobs to change?
> Does not seem to ...
test variants memhp and dimmpxm should be affected by this
(I see your pull req has relevant updates to reference SRAT tables)

> 
> > ---
> > CC: haozhong.zhang@intel.com
> > CC: mst@redhat.com
> > CC: qemu-stable@nongnu.org
> > CC: ehabkost@redhat.com
> > CC: lersek@redhat.com
> > ---
> >  hw/i386/acpi-build.c | 73 +++++++++-------------------------------------------
> >  1 file changed, 12 insertions(+), 61 deletions(-)
> > 
> > diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
> > index e1ee8ae..1599caa 100644
> > --- a/hw/i386/acpi-build.c
> > +++ b/hw/i386/acpi-build.c
> > @@ -2251,64 +2251,6 @@ build_tpm2(GArray *table_data, BIOSLinker *linker, GArray *tcpalog)
> >  #define HOLE_640K_START  (640 * KiB)
> >  #define HOLE_640K_END   (1 * MiB)
> >  
> > -static void build_srat_hotpluggable_memory(GArray *table_data, uint64_t base,
> > -                                           uint64_t len, int default_node)
> > -{
> > -    MemoryDeviceInfoList *info_list = qmp_memory_device_list();
> > -    MemoryDeviceInfoList *info;
> > -    MemoryDeviceInfo *mi;
> > -    PCDIMMDeviceInfo *di;
> > -    uint64_t end = base + len, cur, size;
> > -    bool is_nvdimm;
> > -    AcpiSratMemoryAffinity *numamem;
> > -    MemoryAffinityFlags flags;
> > -
> > -    for (cur = base, info = info_list;
> > -         cur < end;
> > -         cur += size, info = info->next) {
> > -        numamem = acpi_data_push(table_data, sizeof *numamem);
> > -
> > -        if (!info) {
> > -            /*
> > -             * Entry is required for Windows to enable memory hotplug in OS
> > -             * and for Linux to enable SWIOTLB when booted with less than
> > -             * 4G of RAM. Windows works better if the entry sets proximity
> > -             * to the highest NUMA node in the machine at the end of the
> > -             * reserved space.
> > -             * Memory devices may override proximity set by this entry,
> > -             * providing _PXM method if necessary.
> > -             */
> > -            build_srat_memory(numamem, end - 1, 1, default_node,
> > -                              MEM_AFFINITY_HOTPLUGGABLE | MEM_AFFINITY_ENABLED);
> > -            break;
> > -        }
> > -
> > -        mi = info->value;
> > -        is_nvdimm = (mi->type == MEMORY_DEVICE_INFO_KIND_NVDIMM);
> > -        di = !is_nvdimm ? mi->u.dimm.data : mi->u.nvdimm.data;
> > -
> > -        if (cur < di->addr) {
> > -            build_srat_memory(numamem, cur, di->addr - cur, default_node,
> > -                              MEM_AFFINITY_HOTPLUGGABLE | MEM_AFFINITY_ENABLED);
> > -            numamem = acpi_data_push(table_data, sizeof *numamem);
> > -        }
> > -
> > -        size = di->size;
> > -
> > -        flags = MEM_AFFINITY_ENABLED;
> > -        if (di->hotpluggable) {
> > -            flags |= MEM_AFFINITY_HOTPLUGGABLE;
> > -        }
> > -        if (is_nvdimm) {
> > -            flags |= MEM_AFFINITY_NON_VOLATILE;
> > -        }
> > -
> > -        build_srat_memory(numamem, di->addr, size, di->node, flags);
> > -    }
> > -
> > -    qapi_free_MemoryDeviceInfoList(info_list);
> > -}
> > -
> >  static void
> >  build_srat(GArray *table_data, BIOSLinker *linker, MachineState *machine)
> >  {
> > @@ -2414,10 +2356,19 @@ build_srat(GArray *table_data, BIOSLinker *linker, MachineState *machine)
> >          build_srat_memory(numamem, 0, 0, 0, MEM_AFFINITY_NOFLAGS);
> >      }
> >  
> > +    /*
> > +     * Entry is required for Windows to enable memory hotplug in OS
> > +     * and for Linux to enable SWIOTLB when booted with less than
> > +     * 4G of RAM. Windows works better if the entry sets proximity
> > +     * to the highest NUMA node in the machine.
> > +     * Memory devices may override proximity set by this entry,
> > +     * providing _PXM method if necessary.
> > +     */
> >      if (hotplugabble_address_space_size) {
> > -        build_srat_hotpluggable_memory(table_data, machine->device_memory->base,
> > -                                       hotplugabble_address_space_size,
> > -                                       pcms->numa_nodes - 1);
> > +        numamem = acpi_data_push(table_data, sizeof *numamem);
> > +        build_srat_memory(numamem, machine->device_memory->base,
> > +                          hotplugabble_address_space_size, pcms->numa_nodes - 1,
> > +                          MEM_AFFINITY_HOTPLUGGABLE | MEM_AFFINITY_ENABLED);
> >      }
> >  
> >      build_header(linker, table_data,
> > -- 
> > 2.7.4  
>