| Message ID | 1502357028-27465-1-git-send-email-bharata@linux.vnet.ibm.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
On Thu, Aug 10, 2017 at 02:53:48PM +0530, Bharata B Rao wrote: >diff --git a/arch/powerpc/kernel/prom.c b/arch/powerpc/kernel/prom.c >index f830562..24ecf53 100644 >--- a/arch/powerpc/kernel/prom.c >+++ b/arch/powerpc/kernel/prom.c >@@ -524,6 +524,7 @@ static int __init early_init_dt_scan_drconf_memory(unsigned long node) > size = 0x80000000ul - base; > } > memblock_add(base, size); >+ memblock_mark_hotplug(base, size); > } while (--rngs); > } > memblock_dump_all(); Doing this has the effect of putting all the affected memory into ZONE_MOVABLE. See find_zone_movable_pfns_for_nodes(). This means no kernel allocations can occur there. Is that okay? >diff --git a/arch/powerpc/mm/pgtable-radix.c b/arch/powerpc/mm/pgtable-radix.c >index 671a45d..180d25a 100644 >--- a/arch/powerpc/mm/pgtable-radix.c >+++ b/arch/powerpc/mm/pgtable-radix.c >@@ -12,6 +12,7 @@ > #include <linux/memblock.h> > #include <linux/of_fdt.h> > #include <linux/mm.h> >+#include <linux/memory.h> > > #include <asm/pgtable.h> > #include <asm/pgalloc.h> >@@ -255,15 +256,25 @@ static void __init radix_init_pgtable(void) > { > unsigned long rts_field; > struct memblock_region *reg; >+ phys_addr_t addr; >+ u64 lmb_size = memory_block_size_bytes(); > > /* We don't support slb for radix */ > mmu_slb_size = 0; > /* > * Create the linear mapping, using standard page size for now > */ >- for_each_memblock(memory, reg) >- WARN_ON(create_physical_mapping(reg->base, >- reg->base + reg->size)); >+ for_each_memblock(memory, reg) { >+ if (memblock_is_hotpluggable(reg)) { >+ for (addr = reg->base; addr < (reg->base + reg->size); >+ addr += lmb_size) >+ WARN_ON(create_physical_mapping(addr, >+ addr + lmb_size)); >+ } else { >+ WARN_ON(create_physical_mapping(reg->base, >+ reg->base + reg->size)); >+ } >+ } > > /* Find out how many PID bits are supported */ > if (cpu_has_feature(CPU_FTR_HVMODE)) { >-- >2.7.4 >
On Thu, Aug 10, 2017 at 11:50:19AM -0500, Reza Arbab wrote: >On Thu, Aug 10, 2017 at 02:53:48PM +0530, Bharata B Rao wrote: >>diff --git a/arch/powerpc/kernel/prom.c b/arch/powerpc/kernel/prom.c >>index f830562..24ecf53 100644 >>--- a/arch/powerpc/kernel/prom.c >>+++ b/arch/powerpc/kernel/prom.c >>@@ -524,6 +524,7 @@ static int __init early_init_dt_scan_drconf_memory(unsigned long node) >> size = 0x80000000ul - base; >> } >> memblock_add(base, size); >>+ memblock_mark_hotplug(base, size); >> } while (--rngs); >> } >> memblock_dump_all(); > >Doing this has the effect of putting all the affected memory into >ZONE_MOVABLE. See find_zone_movable_pfns_for_nodes(). This means no >kernel allocations can occur there. Is that okay? I should clarify. The behavior change I mention applies when movable_node_is_enabled().
Reza Arbab <arbab@linux.vnet.ibm.com> writes: > On Thu, Aug 10, 2017 at 02:53:48PM +0530, Bharata B Rao wrote: >>diff --git a/arch/powerpc/kernel/prom.c b/arch/powerpc/kernel/prom.c >>index f830562..24ecf53 100644 >>--- a/arch/powerpc/kernel/prom.c >>+++ b/arch/powerpc/kernel/prom.c >>@@ -524,6 +524,7 @@ static int __init early_init_dt_scan_drconf_memory(unsigned long node) >> size = 0x80000000ul - base; >> } >> memblock_add(base, size); >>+ memblock_mark_hotplug(base, size); >> } while (--rngs); >> } >> memblock_dump_all(); > > Doing this has the effect of putting all the affected memory into > ZONE_MOVABLE. See find_zone_movable_pfns_for_nodes(). This means no > kernel allocations can occur there. Is that okay? > So the thinking here is any memory identified via ibm,dynamic-memory can be hot removed later. Hence the need to add them lmb size, because our hotplug framework remove them in lmb size. If we want to support hotunplug, then we will have to make sure kernel allocation doesn't happen in that region right ? With the above i would consider not marking it hotplug was a bug before ? -aneesh
Bharata B Rao <bharata@linux.vnet.ibm.com> writes: > For a PowerKVM guest, it is possible to specify a DIMM device in > addition to the system RAM at boot time. When such a cold plugged DIMM > device is removed from a radix guest, we hit the following warning in the > guest kernel resulting in the eventual failure of memory unplug: > > remove_pud_table: unaligned range > WARNING: CPU: 3 PID: 164 at arch/powerpc/mm/pgtable-radix.c:597 remove_pagetable+0x468/0xca0 > Call Trace: > remove_pagetable+0x464/0xca0 (unreliable) > radix__remove_section_mapping+0x24/0x40 > remove_section_mapping+0x28/0x60 > arch_remove_memory+0xcc/0x120 > remove_memory+0x1ac/0x270 > dlpar_remove_lmb+0x1ac/0x210 > dlpar_memory+0xbc4/0xeb0 > pseries_hp_work_fn+0x1a4/0x230 > process_one_work+0x1cc/0x660 > worker_thread+0xac/0x6d0 > kthread+0x16c/0x1b0 > ret_from_kernel_thread+0x5c/0x74 > > The DIMM memory that is cold plugged gets merged to the same memblock > region as RAM and hence gets mapped at 1G alignment. However since the > removal is done for one LMB (lmb size 256MB) at a time, the address > of the LMB (which is 256MB aligned) would get flagged as unaligned > in remove_pud_table() resulting in the above failure. > > This problem is not seen for hot plugged memory because for the > hot plugged memory, the mappings are created separately for each > LMB and hence they all get aligned at 256MB. > > To fix this problem for the cold plugged memory, let us mark the > cold plugged memblock region explicitly as HOTPLUGGED so that the > region doesn't get merged with RAM. All the memory that is discovered > via ibm,dynamic-memory-configuration is marked so(1). Next identify > such regions in radix_init_pgtable() and create separate mappings > within that region for each LMB so that they get don't get aligned > like RAM region at 1G (2). > > (1) For PowerKVM guests, all boot time memory is represented via > memory@XXXX nodes and hot plugged/pluggable memory is represented via > ibm,dynamic-memory-reconfiguration property. We are marking all > hotplugged memory that is in ASSIGNED state during boot as HOTPLUGGED. > With this only cold plugged memory gets marked for PowerKVM but > need to check how this will affect PowerVM guests. Can you verify this on PowerVM too ? ie we should in most case not find anything under ibm,dynamic-memory-reconfiguration ? -aneesh
On Fri, Aug 11, 2017 at 02:07:51PM +0530, Aneesh Kumar K.V wrote: >Reza Arbab <arbab@linux.vnet.ibm.com> writes: > >> On Thu, Aug 10, 2017 at 02:53:48PM +0530, Bharata B Rao wrote: >>>diff --git a/arch/powerpc/kernel/prom.c b/arch/powerpc/kernel/prom.c >>>index f830562..24ecf53 100644 >>>--- a/arch/powerpc/kernel/prom.c >>>+++ b/arch/powerpc/kernel/prom.c >>>@@ -524,6 +524,7 @@ static int __init early_init_dt_scan_drconf_memory(unsigned long node) >>> size = 0x80000000ul - base; >>> } >>> memblock_add(base, size); >>>+ memblock_mark_hotplug(base, size); >>> } while (--rngs); >>> } >>> memblock_dump_all(); >> >> Doing this has the effect of putting all the affected memory into >> ZONE_MOVABLE. See find_zone_movable_pfns_for_nodes(). This means no >> kernel allocations can occur there. Is that okay? >> > >So the thinking here is any memory identified via ibm,dynamic-memory can >be hot removed later. Hence the need to add them lmb size, because our >hotplug framework remove them in lmb size. If we want to support >hotunplug, then we will have to make sure kernel allocation doesn't >happen in that region right ? Yes, the net result is that this memory can now be hotremoved. I just wanted to point out that the patch doesn't only change the granularity of addition--it also causes the memory to end up in a different zone (when using movable_node). >With the above i would consider not marking it hotplug was a bug before >? Sure, that's reasonable.
On Fri, Aug 11, 2017 at 02:12:04PM +0530, Aneesh Kumar K.V wrote: > Bharata B Rao <bharata@linux.vnet.ibm.com> writes: > > > For a PowerKVM guest, it is possible to specify a DIMM device in > > addition to the system RAM at boot time. When such a cold plugged DIMM > > device is removed from a radix guest, we hit the following warning in the > > guest kernel resulting in the eventual failure of memory unplug: > > > > remove_pud_table: unaligned range > > WARNING: CPU: 3 PID: 164 at arch/powerpc/mm/pgtable-radix.c:597 remove_pagetable+0x468/0xca0 > > Call Trace: > > remove_pagetable+0x464/0xca0 (unreliable) > > radix__remove_section_mapping+0x24/0x40 > > remove_section_mapping+0x28/0x60 > > arch_remove_memory+0xcc/0x120 > > remove_memory+0x1ac/0x270 > > dlpar_remove_lmb+0x1ac/0x210 > > dlpar_memory+0xbc4/0xeb0 > > pseries_hp_work_fn+0x1a4/0x230 > > process_one_work+0x1cc/0x660 > > worker_thread+0xac/0x6d0 > > kthread+0x16c/0x1b0 > > ret_from_kernel_thread+0x5c/0x74 > > > > The DIMM memory that is cold plugged gets merged to the same memblock > > region as RAM and hence gets mapped at 1G alignment. However since the > > removal is done for one LMB (lmb size 256MB) at a time, the address > > of the LMB (which is 256MB aligned) would get flagged as unaligned > > in remove_pud_table() resulting in the above failure. > > > > This problem is not seen for hot plugged memory because for the > > hot plugged memory, the mappings are created separately for each > > LMB and hence they all get aligned at 256MB. > > > > To fix this problem for the cold plugged memory, let us mark the > > cold plugged memblock region explicitly as HOTPLUGGED so that the > > region doesn't get merged with RAM. All the memory that is discovered > > via ibm,dynamic-memory-configuration is marked so(1). Next identify > > such regions in radix_init_pgtable() and create separate mappings > > within that region for each LMB so that they get don't get aligned > > like RAM region at 1G (2). > > > > (1) For PowerKVM guests, all boot time memory is represented via > > memory@XXXX nodes and hot plugged/pluggable memory is represented via > > ibm,dynamic-memory-reconfiguration property. We are marking all > > hotplugged memory that is in ASSIGNED state during boot as HOTPLUGGED. > > With this only cold plugged memory gets marked for PowerKVM but > > need to check how this will affect PowerVM guests. > > Can you verify this on PowerVM too ? ie we should in most case not find > anything under ibm,dynamic-memory-reconfiguration ? Checked with a couple of PowerVM systems. Look like except for RMA which is represented by memory@0, rest of the memory is coming under ibm,dynamic-memory-reconfiguration. So the approach I have taken in this fix wouldn't be optimal on PowerVM ? Regards, Bharata.
On Thu, Aug 10, 2017 at 02:53:48PM +0530, Bharata B Rao wrote: > For a PowerKVM guest, it is possible to specify a DIMM device in > addition to the system RAM at boot time. When such a cold plugged DIMM > device is removed from a radix guest, we hit the following warning in the > guest kernel resulting in the eventual failure of memory unplug: > > remove_pud_table: unaligned range > WARNING: CPU: 3 PID: 164 at arch/powerpc/mm/pgtable-radix.c:597 remove_pagetable+0x468/0xca0 > Call Trace: > remove_pagetable+0x464/0xca0 (unreliable) > radix__remove_section_mapping+0x24/0x40 > remove_section_mapping+0x28/0x60 > arch_remove_memory+0xcc/0x120 > remove_memory+0x1ac/0x270 > dlpar_remove_lmb+0x1ac/0x210 > dlpar_memory+0xbc4/0xeb0 > pseries_hp_work_fn+0x1a4/0x230 > process_one_work+0x1cc/0x660 > worker_thread+0xac/0x6d0 > kthread+0x16c/0x1b0 > ret_from_kernel_thread+0x5c/0x74 > > The DIMM memory that is cold plugged gets merged to the same memblock > region as RAM and hence gets mapped at 1G alignment. However since the > removal is done for one LMB (lmb size 256MB) at a time, the address > of the LMB (which is 256MB aligned) would get flagged as unaligned > in remove_pud_table() resulting in the above failure. > > This problem is not seen for hot plugged memory because for the > hot plugged memory, the mappings are created separately for each > LMB and hence they all get aligned at 256MB. > > To fix this problem for the cold plugged memory, let us mark the > cold plugged memblock region explicitly as HOTPLUGGED so that the > region doesn't get merged with RAM. All the memory that is discovered > via ibm,dynamic-memory-configuration is marked so(1). Next identify > such regions in radix_init_pgtable() and create separate mappings > within that region for each LMB so that they get don't get aligned > like RAM region at 1G (2). > > (1) For PowerKVM guests, all boot time memory is represented via > memory@XXXX nodes and hot plugged/pluggable memory is represented via > ibm,dynamic-memory-reconfiguration property. We are marking all > hotplugged memory that is in ASSIGNED state during boot as HOTPLUGGED. > With this only cold plugged memory gets marked for PowerKVM but > need to check how this will affect PowerVM guests. > > (2) To create separate mappings for every LMB in the hot plugged > region, we need lmb-size. I am currently using memory_block_size_bytes() > API to get the lmb-size. Since this is early init time code, the > machine type isn't probed yet and hence memory_block_size_bytes() > would return the default LMB size as 16MB. Hence we end up creating > separate mappings at much lower granularity than what we can ideally > do for pseries machine. > > Signed-off-by: Bharata B Rao <bharata@linux.vnet.ibm.com> > --- > arch/powerpc/kernel/prom.c | 1 + > arch/powerpc/mm/pgtable-radix.c | 17 ++++++++++++++--- > 2 files changed, 15 insertions(+), 3 deletions(-) > > diff --git a/arch/powerpc/kernel/prom.c b/arch/powerpc/kernel/prom.c > index f830562..24ecf53 100644 > --- a/arch/powerpc/kernel/prom.c > +++ b/arch/powerpc/kernel/prom.c > @@ -524,6 +524,7 @@ static int __init early_init_dt_scan_drconf_memory(unsigned long node) > size = 0x80000000ul - base; > } > memblock_add(base, size); > + memblock_mark_hotplug(base, size); One of the suggestions was to make the above conditional to radix so that PowerVM doesn't get affected by this. However early_radix_enabled() check isn't usable yet at this point and MMU_FTR_TYPE_RADIX will get set only a bit later in early_init_devtree(). Regards, Bharata.
On 09/01/2017 01:53 AM, Bharata B Rao wrote: > On Thu, Aug 10, 2017 at 02:53:48PM +0530, Bharata B Rao wrote: >> For a PowerKVM guest, it is possible to specify a DIMM device in >> addition to the system RAM at boot time. When such a cold plugged DIMM >> device is removed from a radix guest, we hit the following warning in the >> guest kernel resulting in the eventual failure of memory unplug: >> >> remove_pud_table: unaligned range >> WARNING: CPU: 3 PID: 164 at arch/powerpc/mm/pgtable-radix.c:597 remove_pagetable+0x468/0xca0 >> Call Trace: >> remove_pagetable+0x464/0xca0 (unreliable) >> radix__remove_section_mapping+0x24/0x40 >> remove_section_mapping+0x28/0x60 >> arch_remove_memory+0xcc/0x120 >> remove_memory+0x1ac/0x270 >> dlpar_remove_lmb+0x1ac/0x210 >> dlpar_memory+0xbc4/0xeb0 >> pseries_hp_work_fn+0x1a4/0x230 >> process_one_work+0x1cc/0x660 >> worker_thread+0xac/0x6d0 >> kthread+0x16c/0x1b0 >> ret_from_kernel_thread+0x5c/0x74 >> >> The DIMM memory that is cold plugged gets merged to the same memblock >> region as RAM and hence gets mapped at 1G alignment. However since the >> removal is done for one LMB (lmb size 256MB) at a time, the address >> of the LMB (which is 256MB aligned) would get flagged as unaligned >> in remove_pud_table() resulting in the above failure. >> >> This problem is not seen for hot plugged memory because for the >> hot plugged memory, the mappings are created separately for each >> LMB and hence they all get aligned at 256MB. >> >> To fix this problem for the cold plugged memory, let us mark the >> cold plugged memblock region explicitly as HOTPLUGGED so that the >> region doesn't get merged with RAM. All the memory that is discovered >> via ibm,dynamic-memory-configuration is marked so(1). Next identify >> such regions in radix_init_pgtable() and create separate mappings >> within that region for each LMB so that they get don't get aligned >> like RAM region at 1G (2). >> >> (1) For PowerKVM guests, all boot time memory is represented via >> memory@XXXX nodes and hot plugged/pluggable memory is represented via >> ibm,dynamic-memory-reconfiguration property. We are marking all >> hotplugged memory that is in ASSIGNED state during boot as HOTPLUGGED. >> With this only cold plugged memory gets marked for PowerKVM but >> need to check how this will affect PowerVM guests. >> >> (2) To create separate mappings for every LMB in the hot plugged >> region, we need lmb-size. I am currently using memory_block_size_bytes() >> API to get the lmb-size. Since this is early init time code, the >> machine type isn't probed yet and hence memory_block_size_bytes() >> would return the default LMB size as 16MB. Hence we end up creating >> separate mappings at much lower granularity than what we can ideally >> do for pseries machine. >> >> Signed-off-by: Bharata B Rao <bharata@linux.vnet.ibm.com> >> --- >> arch/powerpc/kernel/prom.c | 1 + >> arch/powerpc/mm/pgtable-radix.c | 17 ++++++++++++++--- >> 2 files changed, 15 insertions(+), 3 deletions(-) >> >> diff --git a/arch/powerpc/kernel/prom.c b/arch/powerpc/kernel/prom.c >> index f830562..24ecf53 100644 >> --- a/arch/powerpc/kernel/prom.c >> +++ b/arch/powerpc/kernel/prom.c >> @@ -524,6 +524,7 @@ static int __init early_init_dt_scan_drconf_memory(unsigned long node) >> size = 0x80000000ul - base; >> } >> memblock_add(base, size); >> + memblock_mark_hotplug(base, size); > > One of the suggestions was to make the above conditional to radix so > that PowerVM doesn't get affected by this. However early_radix_enabled() > check isn't usable yet at this point and MMU_FTR_TYPE_RADIX will get set > only a bit later in early_init_devtree(). We do walk the dynamic reconfiguration memory again in the numa code, see parse_drconf_memory() in numa.c, would it far enough along in boot to use early_radix_enabled() and mark the memory hotplug at this point? This may not be the ideal place to mark hotplug memory for radix but it may be nicer than adding another walk of the device tree property somewhere else. -Nathan > > Regards, > Bharata. >
On Fri, Sep 01, 2017 at 09:11:18AM -0500, Nathan Fontenot wrote: > On 09/01/2017 01:53 AM, Bharata B Rao wrote: > > On Thu, Aug 10, 2017 at 02:53:48PM +0530, Bharata B Rao wrote: > >> For a PowerKVM guest, it is possible to specify a DIMM device in > >> addition to the system RAM at boot time. When such a cold plugged DIMM > >> device is removed from a radix guest, we hit the following warning in the > >> guest kernel resulting in the eventual failure of memory unplug: > >> > >> remove_pud_table: unaligned range > >> WARNING: CPU: 3 PID: 164 at arch/powerpc/mm/pgtable-radix.c:597 remove_pagetable+0x468/0xca0 > >> Call Trace: > >> remove_pagetable+0x464/0xca0 (unreliable) > >> radix__remove_section_mapping+0x24/0x40 > >> remove_section_mapping+0x28/0x60 > >> arch_remove_memory+0xcc/0x120 > >> remove_memory+0x1ac/0x270 > >> dlpar_remove_lmb+0x1ac/0x210 > >> dlpar_memory+0xbc4/0xeb0 > >> pseries_hp_work_fn+0x1a4/0x230 > >> process_one_work+0x1cc/0x660 > >> worker_thread+0xac/0x6d0 > >> kthread+0x16c/0x1b0 > >> ret_from_kernel_thread+0x5c/0x74 > >> > >> The DIMM memory that is cold plugged gets merged to the same memblock > >> region as RAM and hence gets mapped at 1G alignment. However since the > >> removal is done for one LMB (lmb size 256MB) at a time, the address > >> of the LMB (which is 256MB aligned) would get flagged as unaligned > >> in remove_pud_table() resulting in the above failure. > >> > >> This problem is not seen for hot plugged memory because for the > >> hot plugged memory, the mappings are created separately for each > >> LMB and hence they all get aligned at 256MB. > >> > >> To fix this problem for the cold plugged memory, let us mark the > >> cold plugged memblock region explicitly as HOTPLUGGED so that the > >> region doesn't get merged with RAM. All the memory that is discovered > >> via ibm,dynamic-memory-configuration is marked so(1). Next identify > >> such regions in radix_init_pgtable() and create separate mappings > >> within that region for each LMB so that they get don't get aligned > >> like RAM region at 1G (2). > >> > >> (1) For PowerKVM guests, all boot time memory is represented via > >> memory@XXXX nodes and hot plugged/pluggable memory is represented via > >> ibm,dynamic-memory-reconfiguration property. We are marking all > >> hotplugged memory that is in ASSIGNED state during boot as HOTPLUGGED. > >> With this only cold plugged memory gets marked for PowerKVM but > >> need to check how this will affect PowerVM guests. > >> > >> (2) To create separate mappings for every LMB in the hot plugged > >> region, we need lmb-size. I am currently using memory_block_size_bytes() > >> API to get the lmb-size. Since this is early init time code, the > >> machine type isn't probed yet and hence memory_block_size_bytes() > >> would return the default LMB size as 16MB. Hence we end up creating > >> separate mappings at much lower granularity than what we can ideally > >> do for pseries machine. > >> > >> Signed-off-by: Bharata B Rao <bharata@linux.vnet.ibm.com> > >> --- > >> arch/powerpc/kernel/prom.c | 1 + > >> arch/powerpc/mm/pgtable-radix.c | 17 ++++++++++++++--- > >> 2 files changed, 15 insertions(+), 3 deletions(-) > >> > >> diff --git a/arch/powerpc/kernel/prom.c b/arch/powerpc/kernel/prom.c > >> index f830562..24ecf53 100644 > >> --- a/arch/powerpc/kernel/prom.c > >> +++ b/arch/powerpc/kernel/prom.c > >> @@ -524,6 +524,7 @@ static int __init early_init_dt_scan_drconf_memory(unsigned long node) > >> size = 0x80000000ul - base; > >> } > >> memblock_add(base, size); > >> + memblock_mark_hotplug(base, size); > > > > One of the suggestions was to make the above conditional to radix so > > that PowerVM doesn't get affected by this. However early_radix_enabled() > > check isn't usable yet at this point and MMU_FTR_TYPE_RADIX will get set > > only a bit later in early_init_devtree(). > > We do walk the dynamic reconfiguration memory again in the numa code, see > parse_drconf_memory() in numa.c, would it far enough along in boot to use > early_radix_enabled() and mark the memory hotplug at this point? parse_drconf_memory() in numa.c happens after radix page tables are setup. Hence setting the hotplugged state from it will not help. Regards, Bharata.
diff --git a/arch/powerpc/kernel/prom.c b/arch/powerpc/kernel/prom.c index f830562..24ecf53 100644 --- a/arch/powerpc/kernel/prom.c +++ b/arch/powerpc/kernel/prom.c @@ -524,6 +524,7 @@ static int __init early_init_dt_scan_drconf_memory(unsigned long node) size = 0x80000000ul - base; } memblock_add(base, size); + memblock_mark_hotplug(base, size); } while (--rngs); } memblock_dump_all(); diff --git a/arch/powerpc/mm/pgtable-radix.c b/arch/powerpc/mm/pgtable-radix.c index 671a45d..180d25a 100644 --- a/arch/powerpc/mm/pgtable-radix.c +++ b/arch/powerpc/mm/pgtable-radix.c @@ -12,6 +12,7 @@ #include <linux/memblock.h> #include <linux/of_fdt.h> #include <linux/mm.h> +#include <linux/memory.h> #include <asm/pgtable.h> #include <asm/pgalloc.h> @@ -255,15 +256,25 @@ static void __init radix_init_pgtable(void) { unsigned long rts_field; struct memblock_region *reg; + phys_addr_t addr; + u64 lmb_size = memory_block_size_bytes(); /* We don't support slb for radix */ mmu_slb_size = 0; /* * Create the linear mapping, using standard page size for now */ - for_each_memblock(memory, reg) - WARN_ON(create_physical_mapping(reg->base, - reg->base + reg->size)); + for_each_memblock(memory, reg) { + if (memblock_is_hotpluggable(reg)) { + for (addr = reg->base; addr < (reg->base + reg->size); + addr += lmb_size) + WARN_ON(create_physical_mapping(addr, + addr + lmb_size)); + } else { + WARN_ON(create_physical_mapping(reg->base, + reg->base + reg->size)); + } + } /* Find out how many PID bits are supported */ if (cpu_has_feature(CPU_FTR_HVMODE)) {
For a PowerKVM guest, it is possible to specify a DIMM device in addition to the system RAM at boot time. When such a cold plugged DIMM device is removed from a radix guest, we hit the following warning in the guest kernel resulting in the eventual failure of memory unplug: remove_pud_table: unaligned range WARNING: CPU: 3 PID: 164 at arch/powerpc/mm/pgtable-radix.c:597 remove_pagetable+0x468/0xca0 Call Trace: remove_pagetable+0x464/0xca0 (unreliable) radix__remove_section_mapping+0x24/0x40 remove_section_mapping+0x28/0x60 arch_remove_memory+0xcc/0x120 remove_memory+0x1ac/0x270 dlpar_remove_lmb+0x1ac/0x210 dlpar_memory+0xbc4/0xeb0 pseries_hp_work_fn+0x1a4/0x230 process_one_work+0x1cc/0x660 worker_thread+0xac/0x6d0 kthread+0x16c/0x1b0 ret_from_kernel_thread+0x5c/0x74 The DIMM memory that is cold plugged gets merged to the same memblock region as RAM and hence gets mapped at 1G alignment. However since the removal is done for one LMB (lmb size 256MB) at a time, the address of the LMB (which is 256MB aligned) would get flagged as unaligned in remove_pud_table() resulting in the above failure. This problem is not seen for hot plugged memory because for the hot plugged memory, the mappings are created separately for each LMB and hence they all get aligned at 256MB. To fix this problem for the cold plugged memory, let us mark the cold plugged memblock region explicitly as HOTPLUGGED so that the region doesn't get merged with RAM. All the memory that is discovered via ibm,dynamic-memory-configuration is marked so(1). Next identify such regions in radix_init_pgtable() and create separate mappings within that region for each LMB so that they get don't get aligned like RAM region at 1G (2). (1) For PowerKVM guests, all boot time memory is represented via memory@XXXX nodes and hot plugged/pluggable memory is represented via ibm,dynamic-memory-reconfiguration property. We are marking all hotplugged memory that is in ASSIGNED state during boot as HOTPLUGGED. With this only cold plugged memory gets marked for PowerKVM but need to check how this will affect PowerVM guests. (2) To create separate mappings for every LMB in the hot plugged region, we need lmb-size. I am currently using memory_block_size_bytes() API to get the lmb-size. Since this is early init time code, the machine type isn't probed yet and hence memory_block_size_bytes() would return the default LMB size as 16MB. Hence we end up creating separate mappings at much lower granularity than what we can ideally do for pseries machine. Signed-off-by: Bharata B Rao <bharata@linux.vnet.ibm.com> --- arch/powerpc/kernel/prom.c | 1 + arch/powerpc/mm/pgtable-radix.c | 17 ++++++++++++++--- 2 files changed, 15 insertions(+), 3 deletions(-)