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[PULL,1/2] spapr: Error out when CPU hotplug is attempted on older pseries machines

Message ID 1470201951-19288-2-git-send-email-david@gibson.dropbear.id.au
State New
Headers show

Commit Message

David Gibson Aug. 3, 2016, 5:25 a.m. UTC 
From: Bharata B Rao <bharata@linux.vnet.ibm.com>

CPU hotplug and coldplug aren't supported prior to pseries-2.7.  Further,
earlier machine types don't use CPU core objects at all.  These mean that
query-hotpluggable-cpus and coldplug on older pseries machines will crash
QEMU.  It also means that hotpluggable_cpus flag in query-machines will
be incorrectly set to true for pseries < 2.7, since it is based on the
presence of the query_hotpluggable_cpus hook.

- Don't assign the query_hotpluggable_cpus hook for pseries < 2.7
- query_hotpluggable_cpus should therefore never be called on pseries <
  2.7, so add an assert
- spapr_core_pre_plug() should fail hot/cold plug attempts for pseries <
  2.7, since core objects are never used there
- spapr_core_plug() should therefore never be called for pseries < 2.7, so
  add an assert.

Signed-off-by: Bharata B Rao <bharata@linux.vnet.ibm.com>
[dwg: Change from query_hotpluggable_cpus returning NULL for pseries < 2.7
 to not being called at all, reword commit message for accuracy]
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
---
 hw/ppc/spapr.c          |  7 ++++++-
 hw/ppc/spapr_cpu_core.c | 19 ++++++-------------
 2 files changed, 12 insertions(+), 14 deletions(-)

Comments

Bharata B Rao Aug. 4, 2016, 10:44 a.m. UTC | #1 
On Wed, Aug 03, 2016 at 03:25:50PM +1000, David Gibson wrote:
> From: Bharata B Rao <bharata@linux.vnet.ibm.com>
> 
> CPU hotplug and coldplug aren't supported prior to pseries-2.7.  Further,
> earlier machine types don't use CPU core objects at all.  These mean that
> query-hotpluggable-cpus and coldplug on older pseries machines will crash
> QEMU.  It also means that hotpluggable_cpus flag in query-machines will
> be incorrectly set to true for pseries < 2.7, since it is based on the
> presence of the query_hotpluggable_cpus hook.
> 
> - Don't assign the query_hotpluggable_cpus hook for pseries < 2.7
> - query_hotpluggable_cpus should therefore never be called on pseries <
>   2.7, so add an assert
> - spapr_core_pre_plug() should fail hot/cold plug attempts for pseries <
>   2.7, since core objects are never used there
> - spapr_core_plug() should therefore never be called for pseries < 2.7, so
>   add an assert.
> 
> Signed-off-by: Bharata B Rao <bharata@linux.vnet.ibm.com>
> [dwg: Change from query_hotpluggable_cpus returning NULL for pseries < 2.7
>  to not being called at all, reword commit message for accuracy]
> Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
> ---
>  hw/ppc/spapr.c          |  7 ++++++-
>  hw/ppc/spapr_cpu_core.c | 19 ++++++-------------
>  2 files changed, 12 insertions(+), 14 deletions(-)
> 
> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> index fbbd051..bce2371 100644
> --- a/hw/ppc/spapr.c
> +++ b/hw/ppc/spapr.c
> @@ -2376,8 +2376,11 @@ static HotpluggableCPUList *spapr_query_hotpluggable_cpus(MachineState *machine)
>      int i;
>      HotpluggableCPUList *head = NULL;
>      sPAPRMachineState *spapr = SPAPR_MACHINE(machine);
> +    sPAPRMachineClass *smc = SPAPR_MACHINE_GET_CLASS(machine);
>      int spapr_max_cores = max_cpus / smp_threads;
> 
> +    g_assert(smc->dr_cpu_enabled);
> +
>      for (i = 0; i < spapr_max_cores; i++) {
>          HotpluggableCPUList *list_item = g_new0(typeof(*list_item), 1);
>          HotpluggableCPU *cpu_item = g_new0(typeof(*cpu_item), 1);
> @@ -2432,7 +2435,9 @@ static void spapr_machine_class_init(ObjectClass *oc, void *data)
>      hc->plug = spapr_machine_device_plug;
>      hc->unplug = spapr_machine_device_unplug;
>      mc->cpu_index_to_socket_id = spapr_cpu_index_to_socket_id;
> -    mc->query_hotpluggable_cpus = spapr_query_hotpluggable_cpus;
> +    if (smc->dr_cpu_enabled) {
> +        mc->query_hotpluggable_cpus = spapr_query_hotpluggable_cpus;
> +    }
> 
>      smc->dr_lmb_enabled = true;
>      smc->dr_cpu_enabled = true;

Unfortunately smc->dr_cpu_enabled is always false when you set
mc->query_hotpluggable_cpus and will be set to true immediately
afterwards as seen in above hunk.

This leads to query-hotpluggable-cpus being unavailable for all
machine type versions. Your first version of setting
mc->query_hotpluggable_cpus to NULL explicitly for 2.6 and downwards
was correct.

Regards,
Bharata.
David Gibson Aug. 5, 2016, 2:16 a.m. UTC | #2 
On Thu, Aug 04, 2016 at 04:14:53PM +0530, Bharata B Rao wrote:
> On Wed, Aug 03, 2016 at 03:25:50PM +1000, David Gibson wrote:
> > From: Bharata B Rao <bharata@linux.vnet.ibm.com>
> > 
> > CPU hotplug and coldplug aren't supported prior to pseries-2.7.  Further,
> > earlier machine types don't use CPU core objects at all.  These mean that
> > query-hotpluggable-cpus and coldplug on older pseries machines will crash
> > QEMU.  It also means that hotpluggable_cpus flag in query-machines will
> > be incorrectly set to true for pseries < 2.7, since it is based on the
> > presence of the query_hotpluggable_cpus hook.
> > 
> > - Don't assign the query_hotpluggable_cpus hook for pseries < 2.7
> > - query_hotpluggable_cpus should therefore never be called on pseries <
> >   2.7, so add an assert
> > - spapr_core_pre_plug() should fail hot/cold plug attempts for pseries <
> >   2.7, since core objects are never used there
> > - spapr_core_plug() should therefore never be called for pseries < 2.7, so
> >   add an assert.
> > 
> > Signed-off-by: Bharata B Rao <bharata@linux.vnet.ibm.com>
> > [dwg: Change from query_hotpluggable_cpus returning NULL for pseries < 2.7
> >  to not being called at all, reword commit message for accuracy]
> > Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
> > ---
> >  hw/ppc/spapr.c          |  7 ++++++-
> >  hw/ppc/spapr_cpu_core.c | 19 ++++++-------------
> >  2 files changed, 12 insertions(+), 14 deletions(-)
> > 
> > diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> > index fbbd051..bce2371 100644
> > --- a/hw/ppc/spapr.c
> > +++ b/hw/ppc/spapr.c
> > @@ -2376,8 +2376,11 @@ static HotpluggableCPUList *spapr_query_hotpluggable_cpus(MachineState *machine)
> >      int i;
> >      HotpluggableCPUList *head = NULL;
> >      sPAPRMachineState *spapr = SPAPR_MACHINE(machine);
> > +    sPAPRMachineClass *smc = SPAPR_MACHINE_GET_CLASS(machine);
> >      int spapr_max_cores = max_cpus / smp_threads;
> > 
> > +    g_assert(smc->dr_cpu_enabled);
> > +
> >      for (i = 0; i < spapr_max_cores; i++) {
> >          HotpluggableCPUList *list_item = g_new0(typeof(*list_item), 1);
> >          HotpluggableCPU *cpu_item = g_new0(typeof(*cpu_item), 1);
> > @@ -2432,7 +2435,9 @@ static void spapr_machine_class_init(ObjectClass *oc, void *data)
> >      hc->plug = spapr_machine_device_plug;
> >      hc->unplug = spapr_machine_device_unplug;
> >      mc->cpu_index_to_socket_id = spapr_cpu_index_to_socket_id;
> > -    mc->query_hotpluggable_cpus = spapr_query_hotpluggable_cpus;
> > +    if (smc->dr_cpu_enabled) {
> > +        mc->query_hotpluggable_cpus = spapr_query_hotpluggable_cpus;
> > +    }
> > 
> >      smc->dr_lmb_enabled = true;
> >      smc->dr_cpu_enabled = true;
> 
> Unfortunately smc->dr_cpu_enabled is always false when you set
> mc->query_hotpluggable_cpus and will be set to true immediately
> afterwards as seen in above hunk.
> 
> This leads to query-hotpluggable-cpus being unavailable for all
> machine type versions. Your first version of setting
> mc->query_hotpluggable_cpus to NULL explicitly for 2.6 and downwards
> was correct.

*facepalm* I can't believe I forgot to check that.


In fact.. we could just replace dr_lmb_enabled with the NULL or
not-NULL status of query_hotpluggable_cpus.

I'll send a fix shortly.
diff mbox

Patch

diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index fbbd051..bce2371 100644
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -2376,8 +2376,11 @@  static HotpluggableCPUList *spapr_query_hotpluggable_cpus(MachineState *machine)
     int i;
     HotpluggableCPUList *head = NULL;
     sPAPRMachineState *spapr = SPAPR_MACHINE(machine);
+    sPAPRMachineClass *smc = SPAPR_MACHINE_GET_CLASS(machine);
     int spapr_max_cores = max_cpus / smp_threads;
 
+    g_assert(smc->dr_cpu_enabled);
+
     for (i = 0; i < spapr_max_cores; i++) {
         HotpluggableCPUList *list_item = g_new0(typeof(*list_item), 1);
         HotpluggableCPU *cpu_item = g_new0(typeof(*cpu_item), 1);
@@ -2432,7 +2435,9 @@  static void spapr_machine_class_init(ObjectClass *oc, void *data)
     hc->plug = spapr_machine_device_plug;
     hc->unplug = spapr_machine_device_unplug;
     mc->cpu_index_to_socket_id = spapr_cpu_index_to_socket_id;
-    mc->query_hotpluggable_cpus = spapr_query_hotpluggable_cpus;
+    if (smc->dr_cpu_enabled) {
+        mc->query_hotpluggable_cpus = spapr_query_hotpluggable_cpus;
+    }
 
     smc->dr_lmb_enabled = true;
     smc->dr_cpu_enabled = true;
diff --git a/hw/ppc/spapr_cpu_core.c b/hw/ppc/spapr_cpu_core.c
index ec81ee6..170ed15 100644
--- a/hw/ppc/spapr_cpu_core.c
+++ b/hw/ppc/spapr_cpu_core.c
@@ -166,18 +166,11 @@  void spapr_core_plug(HotplugHandler *hotplug_dev, DeviceState *dev,
     int index = cc->core_id / smp_threads;
     int smt = kvmppc_smt_threads();
 
+    g_assert(smc->dr_cpu_enabled);
+
     drc = spapr_dr_connector_by_id(SPAPR_DR_CONNECTOR_TYPE_CPU, index * smt);
     spapr->cores[index] = OBJECT(dev);
 
-    if (!smc->dr_cpu_enabled) {
-        /*
-         * This is a cold plugged CPU core but the machine doesn't support
-         * DR. So skip the hotplug path ensuring that the core is brought
-         * up online with out an associated DR connector.
-         */
-        return;
-    }
-
     g_assert(drc);
 
     /*
@@ -225,13 +218,13 @@  void spapr_core_pre_plug(HotplugHandler *hotplug_dev, DeviceState *dev,
     char *base_core_type = spapr_get_cpu_core_type(machine->cpu_model);
     const char *type = object_get_typename(OBJECT(dev));
 
-    if (strcmp(base_core_type, type)) {
-        error_setg(&local_err, "CPU core type should be %s", base_core_type);
+    if (!smc->dr_cpu_enabled) {
+        error_setg(&local_err, "CPU hotplug not supported for this machine");
         goto out;
     }
 
-    if (!smc->dr_cpu_enabled && dev->hotplugged) {
-        error_setg(&local_err, "CPU hotplug not supported for this machine");
+    if (strcmp(base_core_type, type)) {
+        error_setg(&local_err, "CPU core type should be %s", base_core_type);
         goto out;
     }