[Qemu-devel] [PATCH] spapr: Correct compatibility mode setting for hotplugged CPUs

[Qemu-devel] [PATCH] spapr: Correct compatibility mode setting for hotplugged CPUs

[David Gibson]

Currently the pseries machine sets the compatibility mode for the
guest's cpus in two places: 1) at machine reset and 2) after CAS
negotiation.

This means that if we set or negotiate a compatiblity mode, then
hotplug a cpu, the hotplugged cpu doesn't get the right mode set and
will incorrectly have the full native features.

To correct this, we set the compatibility mode on a cpu when it is
brought online with the 'start-cpu' RTAS call.  Given that we no
longer need to set the compatibility mode on all CPUs at machine
reset, so we change that to only set the mode for the boot cpu.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
---
 hw/ppc/spapr.c      | 2 +-
 hw/ppc/spapr_rtas.c | 8 ++++++++
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index e22888ba06..d1acfe8858 100644
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -1510,7 +1510,7 @@ static void spapr_machine_reset(void)
         spapr_ovec_cleanup(spapr->ov5_cas);
         spapr->ov5_cas = spapr_ovec_new();
 
-        ppc_set_compat_all(spapr->max_compat_pvr, &error_fatal);
+        ppc_set_compat(first_ppc_cpu, spapr->max_compat_pvr, &error_fatal);
     }
 
     fdt = spapr_build_fdt(spapr, rtas_addr, spapr->rtas_size);
diff --git a/hw/ppc/spapr_rtas.c b/hw/ppc/spapr_rtas.c
index 4bb939d3d1..2ed00548c1 100644
--- a/hw/ppc/spapr_rtas.c
+++ b/hw/ppc/spapr_rtas.c
@@ -163,6 +163,7 @@ static void rtas_start_cpu(PowerPCCPU *cpu_, sPAPRMachineState *spapr,
         CPUState *cs = CPU(cpu);
         CPUPPCState *env = &cpu->env;
         PowerPCCPUClass *pcc = POWERPC_CPU_GET_CLASS(cpu);
+        Error *local_err = NULL;
 
         if (!cs->halted) {
             rtas_st(rets, 0, RTAS_OUT_HW_ERROR);
@@ -174,6 +175,13 @@ static void rtas_start_cpu(PowerPCCPU *cpu_, sPAPRMachineState *spapr,
          * new cpu enters */
         kvm_cpu_synchronize_state(cs);
 
+        /* Set compatibility mode to match existing cpus */
+        ppc_set_compat(cpu, POWERPC_CPU(first_cpu)->compat_pvr, &local_err);
+        if (local_err) {
+            rtas_st(rets, 0, RTAS_OUT_HW_ERROR);
+            return;
+        }
+
         env->msr = (1ULL << MSR_SF) | (1ULL << MSR_ME);
 
         /* Enable Power-saving mode Exit Cause exceptions for the new CPU */
-- 
2.14.3

Re: [Qemu-devel] [PATCH] spapr: Correct compatibility mode setting for hotplugged CPUs

[Alexey Kardashevskiy]

On 04/01/18 15:24, David Gibson wrote:
> Currently the pseries machine sets the compatibility mode for the
> guest's cpus in two places: 1) at machine reset and 2) after CAS
> negotiation.
> 
> This means that if we set or negotiate a compatiblity mode, then
> hotplug a cpu, the hotplugged cpu doesn't get the right mode set and
> will incorrectly have the full native features.
> 
> To correct this, we set the compatibility mode on a cpu when it is
> brought online with the 'start-cpu' RTAS call.  Given that we no
> longer need to set the compatibility mode on all CPUs at machine
> reset, so we change that to only set the mode for the boot cpu.
> 
> Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

Reviewed-by: Alexey Kardashevskiy <aik@ozlabs.ru>


> ---
>  hw/ppc/spapr.c      | 2 +-
>  hw/ppc/spapr_rtas.c | 8 ++++++++
>  2 files changed, 9 insertions(+), 1 deletion(-)
> 
> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> index e22888ba06..d1acfe8858 100644
> --- a/hw/ppc/spapr.c
> +++ b/hw/ppc/spapr.c
> @@ -1510,7 +1510,7 @@ static void spapr_machine_reset(void)
>          spapr_ovec_cleanup(spapr->ov5_cas);
>          spapr->ov5_cas = spapr_ovec_new();
>  
> -        ppc_set_compat_all(spapr->max_compat_pvr, &error_fatal);
> +        ppc_set_compat(first_ppc_cpu, spapr->max_compat_pvr, &error_fatal);
>      }
>  
>      fdt = spapr_build_fdt(spapr, rtas_addr, spapr->rtas_size);
> diff --git a/hw/ppc/spapr_rtas.c b/hw/ppc/spapr_rtas.c
> index 4bb939d3d1..2ed00548c1 100644
> --- a/hw/ppc/spapr_rtas.c
> +++ b/hw/ppc/spapr_rtas.c
> @@ -163,6 +163,7 @@ static void rtas_start_cpu(PowerPCCPU *cpu_, sPAPRMachineState *spapr,
>          CPUState *cs = CPU(cpu);
>          CPUPPCState *env = &cpu->env;
>          PowerPCCPUClass *pcc = POWERPC_CPU_GET_CLASS(cpu);
> +        Error *local_err = NULL;
>  
>          if (!cs->halted) {
>              rtas_st(rets, 0, RTAS_OUT_HW_ERROR);
> @@ -174,6 +175,13 @@ static void rtas_start_cpu(PowerPCCPU *cpu_, sPAPRMachineState *spapr,
>           * new cpu enters */
>          kvm_cpu_synchronize_state(cs);
>  
> +        /* Set compatibility mode to match existing cpus */
> +        ppc_set_compat(cpu, POWERPC_CPU(first_cpu)->compat_pvr, &local_err);
> +        if (local_err) {
> +            rtas_st(rets, 0, RTAS_OUT_HW_ERROR);
> +            return;
> +        }
> +
>          env->msr = (1ULL << MSR_SF) | (1ULL << MSR_ME);
>  
>          /* Enable Power-saving mode Exit Cause exceptions for the new CPU */
> 


-- 
Alexey

Re: [Qemu-devel] [PATCH] spapr: Correct compatibility mode setting for hotplugged CPUs

[Greg Kurz]

On Thu,  4 Jan 2018 15:24:05 +1100
David Gibson <david@gibson.dropbear.id.au> wrote:

> Currently the pseries machine sets the compatibility mode for the
> guest's cpus in two places: 1) at machine reset and 2) after CAS
> negotiation.
> 
> This means that if we set or negotiate a compatiblity mode, then
> hotplug a cpu, the hotplugged cpu doesn't get the right mode set and
> will incorrectly have the full native features.
> 
> To correct this, we set the compatibility mode on a cpu when it is
> brought online with the 'start-cpu' RTAS call.  Given that we no
> longer need to set the compatibility mode on all CPUs at machine
> reset, so we change that to only set the mode for the boot cpu.
> 
> Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
> ---
>  hw/ppc/spapr.c      | 2 +-
>  hw/ppc/spapr_rtas.c | 8 ++++++++
>  2 files changed, 9 insertions(+), 1 deletion(-)
> 
> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> index e22888ba06..d1acfe8858 100644
> --- a/hw/ppc/spapr.c
> +++ b/hw/ppc/spapr.c
> @@ -1510,7 +1510,7 @@ static void spapr_machine_reset(void)
>          spapr_ovec_cleanup(spapr->ov5_cas);
>          spapr->ov5_cas = spapr_ovec_new();
>  
> -        ppc_set_compat_all(spapr->max_compat_pvr, &error_fatal);
> +        ppc_set_compat(first_ppc_cpu, spapr->max_compat_pvr, &error_fatal);
>      }
>  
>      fdt = spapr_build_fdt(spapr, rtas_addr, spapr->rtas_size);
> diff --git a/hw/ppc/spapr_rtas.c b/hw/ppc/spapr_rtas.c
> index 4bb939d3d1..2ed00548c1 100644
> --- a/hw/ppc/spapr_rtas.c
> +++ b/hw/ppc/spapr_rtas.c
> @@ -163,6 +163,7 @@ static void rtas_start_cpu(PowerPCCPU *cpu_, sPAPRMachineState *spapr,
>          CPUState *cs = CPU(cpu);
>          CPUPPCState *env = &cpu->env;
>          PowerPCCPUClass *pcc = POWERPC_CPU_GET_CLASS(cpu);
> +        Error *local_err = NULL;
>  
>          if (!cs->halted) {
>              rtas_st(rets, 0, RTAS_OUT_HW_ERROR);
> @@ -174,6 +175,13 @@ static void rtas_start_cpu(PowerPCCPU *cpu_, sPAPRMachineState *spapr,
>           * new cpu enters */
>          kvm_cpu_synchronize_state(cs);
>  
> +        /* Set compatibility mode to match existing cpus */
> +        ppc_set_compat(cpu, POWERPC_CPU(first_cpu)->compat_pvr, &local_err);

Is it okay to report a simple HW error to the guest here instead of aborting
like we do with first_cpu at reset time ?

> +        if (local_err) {
> +            rtas_st(rets, 0, RTAS_OUT_HW_ERROR);
> +            return;
> +        }
> +
>          env->msr = (1ULL << MSR_SF) | (1ULL << MSR_ME);
>  
>          /* Enable Power-saving mode Exit Cause exceptions for the new CPU */

Re: [Qemu-devel] [Qemu-ppc] [PATCH] spapr: Correct compatibility mode setting for hotplugged CPUs

[Daniel Henrique Barboza]

On 01/04/2018 02:24 AM, David Gibson wrote:
> Currently the pseries machine sets the compatibility mode for the
> guest's cpus in two places: 1) at machine reset and 2) after CAS
> negotiation.
>
> This means that if we set or negotiate a compatiblity mode, then

s/compatiblity/compatibility

> hotplug a cpu, the hotplugged cpu doesn't get the right mode set and
> will incorrectly have the full native features.
>
> To correct this, we set the compatibility mode on a cpu when it is
> brought online with the 'start-cpu' RTAS call.  Given that we no
> longer need to set the compatibility mode on all CPUs at machine
> reset, so we change that to only set the mode for the boot cpu.
>
> Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
> ---
Reviewed-by: Daniel Henrique Barboza <danielhb@linux.vnet.ibm.com>
>   hw/ppc/spapr.c      | 2 +-
>   hw/ppc/spapr_rtas.c | 8 ++++++++
>   2 files changed, 9 insertions(+), 1 deletion(-)
>
> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> index e22888ba06..d1acfe8858 100644
> --- a/hw/ppc/spapr.c
> +++ b/hw/ppc/spapr.c
> @@ -1510,7 +1510,7 @@ static void spapr_machine_reset(void)
>           spapr_ovec_cleanup(spapr->ov5_cas);
>           spapr->ov5_cas = spapr_ovec_new();
>
> -        ppc_set_compat_all(spapr->max_compat_pvr, &error_fatal);
> +        ppc_set_compat(first_ppc_cpu, spapr->max_compat_pvr, &error_fatal);
>       }
>
>       fdt = spapr_build_fdt(spapr, rtas_addr, spapr->rtas_size);
> diff --git a/hw/ppc/spapr_rtas.c b/hw/ppc/spapr_rtas.c
> index 4bb939d3d1..2ed00548c1 100644
> --- a/hw/ppc/spapr_rtas.c
> +++ b/hw/ppc/spapr_rtas.c
> @@ -163,6 +163,7 @@ static void rtas_start_cpu(PowerPCCPU *cpu_, sPAPRMachineState *spapr,
>           CPUState *cs = CPU(cpu);
>           CPUPPCState *env = &cpu->env;
>           PowerPCCPUClass *pcc = POWERPC_CPU_GET_CLASS(cpu);
> +        Error *local_err = NULL;
>
>           if (!cs->halted) {
>               rtas_st(rets, 0, RTAS_OUT_HW_ERROR);
> @@ -174,6 +175,13 @@ static void rtas_start_cpu(PowerPCCPU *cpu_, sPAPRMachineState *spapr,
>            * new cpu enters */
>           kvm_cpu_synchronize_state(cs);
>
> +        /* Set compatibility mode to match existing cpus */
> +        ppc_set_compat(cpu, POWERPC_CPU(first_cpu)->compat_pvr, &local_err);
> +        if (local_err) {
> +            rtas_st(rets, 0, RTAS_OUT_HW_ERROR);
> +            return;
> +        }
> +
>           env->msr = (1ULL << MSR_SF) | (1ULL << MSR_ME);
>
>           /* Enable Power-saving mode Exit Cause exceptions for the new CPU */

Re: [Qemu-devel] [PATCH] spapr: Correct compatibility mode setting for hotplugged CPUs

[Michael Roth]

Quoting Greg Kurz (2018-01-04 11:47:18)
> On Thu,  4 Jan 2018 15:24:05 +1100
> David Gibson <david@gibson.dropbear.id.au> wrote:
> 
> > Currently the pseries machine sets the compatibility mode for the
> > guest's cpus in two places: 1) at machine reset and 2) after CAS
> > negotiation.
> > 
> > This means that if we set or negotiate a compatiblity mode, then
> > hotplug a cpu, the hotplugged cpu doesn't get the right mode set and
> > will incorrectly have the full native features.
> > 
> > To correct this, we set the compatibility mode on a cpu when it is
> > brought online with the 'start-cpu' RTAS call.  Given that we no
> > longer need to set the compatibility mode on all CPUs at machine
> > reset, so we change that to only set the mode for the boot cpu.
> > 
> > Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
> > ---
> >  hw/ppc/spapr.c      | 2 +-
> >  hw/ppc/spapr_rtas.c | 8 ++++++++
> >  2 files changed, 9 insertions(+), 1 deletion(-)
> > 
> > diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> > index e22888ba06..d1acfe8858 100644
> > --- a/hw/ppc/spapr.c
> > +++ b/hw/ppc/spapr.c
> > @@ -1510,7 +1510,7 @@ static void spapr_machine_reset(void)
> >          spapr_ovec_cleanup(spapr->ov5_cas);
> >          spapr->ov5_cas = spapr_ovec_new();
> >  
> > -        ppc_set_compat_all(spapr->max_compat_pvr, &error_fatal);
> > +        ppc_set_compat(first_ppc_cpu, spapr->max_compat_pvr, &error_fatal);
> >      }
> >  
> >      fdt = spapr_build_fdt(spapr, rtas_addr, spapr->rtas_size);
> > diff --git a/hw/ppc/spapr_rtas.c b/hw/ppc/spapr_rtas.c
> > index 4bb939d3d1..2ed00548c1 100644
> > --- a/hw/ppc/spapr_rtas.c
> > +++ b/hw/ppc/spapr_rtas.c
> > @@ -163,6 +163,7 @@ static void rtas_start_cpu(PowerPCCPU *cpu_, sPAPRMachineState *spapr,
> >          CPUState *cs = CPU(cpu);
> >          CPUPPCState *env = &cpu->env;
> >          PowerPCCPUClass *pcc = POWERPC_CPU_GET_CLASS(cpu);
> > +        Error *local_err = NULL;
> >  
> >          if (!cs->halted) {
> >              rtas_st(rets, 0, RTAS_OUT_HW_ERROR);
> > @@ -174,6 +175,13 @@ static void rtas_start_cpu(PowerPCCPU *cpu_, sPAPRMachineState *spapr,
> >           * new cpu enters */
> >          kvm_cpu_synchronize_state(cs);
> >  
> > +        /* Set compatibility mode to match existing cpus */
> > +        ppc_set_compat(cpu, POWERPC_CPU(first_cpu)->compat_pvr, &local_err);
> 
> Is it okay to report a simple HW error to the guest here instead of aborting
> like we do with first_cpu at reset time ?

And if we don't opt for &error_fatal, we need an error_free() below.

> 
> > +        if (local_err) {
> > +            rtas_st(rets, 0, RTAS_OUT_HW_ERROR);
> > +            return;
> > +        }
> > +
> >          env->msr = (1ULL << MSR_SF) | (1ULL << MSR_ME);
> >  
> >          /* Enable Power-saving mode Exit Cause exceptions for the new CPU */
> 

Re: [Qemu-devel] [PATCH] spapr: Correct compatibility mode setting for hotplugged CPUs

[David Gibson]

[-- Attachment #1: Type: text/plain, Size: 3262 bytes --]

On Thu, Jan 04, 2018 at 06:47:18PM +0100, Greg Kurz wrote:
> On Thu,  4 Jan 2018 15:24:05 +1100
> David Gibson <david@gibson.dropbear.id.au> wrote:
> 
> > Currently the pseries machine sets the compatibility mode for the
> > guest's cpus in two places: 1) at machine reset and 2) after CAS
> > negotiation.
> > 
> > This means that if we set or negotiate a compatiblity mode, then
> > hotplug a cpu, the hotplugged cpu doesn't get the right mode set and
> > will incorrectly have the full native features.
> > 
> > To correct this, we set the compatibility mode on a cpu when it is
> > brought online with the 'start-cpu' RTAS call.  Given that we no
> > longer need to set the compatibility mode on all CPUs at machine
> > reset, so we change that to only set the mode for the boot cpu.
> > 
> > Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
> > ---
> >  hw/ppc/spapr.c      | 2 +-
> >  hw/ppc/spapr_rtas.c | 8 ++++++++
> >  2 files changed, 9 insertions(+), 1 deletion(-)
> > 
> > diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> > index e22888ba06..d1acfe8858 100644
> > --- a/hw/ppc/spapr.c
> > +++ b/hw/ppc/spapr.c
> > @@ -1510,7 +1510,7 @@ static void spapr_machine_reset(void)
> >          spapr_ovec_cleanup(spapr->ov5_cas);
> >          spapr->ov5_cas = spapr_ovec_new();
> >  
> > -        ppc_set_compat_all(spapr->max_compat_pvr, &error_fatal);
> > +        ppc_set_compat(first_ppc_cpu, spapr->max_compat_pvr, &error_fatal);
> >      }
> >  
> >      fdt = spapr_build_fdt(spapr, rtas_addr, spapr->rtas_size);
> > diff --git a/hw/ppc/spapr_rtas.c b/hw/ppc/spapr_rtas.c
> > index 4bb939d3d1..2ed00548c1 100644
> > --- a/hw/ppc/spapr_rtas.c
> > +++ b/hw/ppc/spapr_rtas.c
> > @@ -163,6 +163,7 @@ static void rtas_start_cpu(PowerPCCPU *cpu_, sPAPRMachineState *spapr,
> >          CPUState *cs = CPU(cpu);
> >          CPUPPCState *env = &cpu->env;
> >          PowerPCCPUClass *pcc = POWERPC_CPU_GET_CLASS(cpu);
> > +        Error *local_err = NULL;
> >  
> >          if (!cs->halted) {
> >              rtas_st(rets, 0, RTAS_OUT_HW_ERROR);
> > @@ -174,6 +175,13 @@ static void rtas_start_cpu(PowerPCCPU *cpu_, sPAPRMachineState *spapr,
> >           * new cpu enters */
> >          kvm_cpu_synchronize_state(cs);
> >  
> > +        /* Set compatibility mode to match existing cpus */
> > +        ppc_set_compat(cpu, POWERPC_CPU(first_cpu)->compat_pvr, &local_err);
> 
> Is it okay to report a simple HW error to the guest here instead of aborting
> like we do with first_cpu at reset time ?

Should be: this happens before we turn the cpu on, so the effect will
be that the guest fails to online the cpu.  That seems like a better
failure mode than killing the already running guest.

> 
> > +        if (local_err) {
> > +            rtas_st(rets, 0, RTAS_OUT_HW_ERROR);
> > +            return;
> > +        }
> > +
> >          env->msr = (1ULL << MSR_SF) | (1ULL << MSR_ME);
> >  
> >          /* Enable Power-saving mode Exit Cause exceptions for the new CPU */
> 

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

[-- Attachment #2: signature.asc --]
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Re: [Qemu-devel] [PATCH] spapr: Correct compatibility mode setting for hotplugged CPUs

[David Gibson]

[-- Attachment #1: Type: text/plain, Size: 3428 bytes --]

On Thu, Jan 04, 2018 at 03:11:03PM -0600, Michael Roth wrote:
> Quoting Greg Kurz (2018-01-04 11:47:18)
> > On Thu,  4 Jan 2018 15:24:05 +1100
> > David Gibson <david@gibson.dropbear.id.au> wrote:
> > 
> > > Currently the pseries machine sets the compatibility mode for the
> > > guest's cpus in two places: 1) at machine reset and 2) after CAS
> > > negotiation.
> > > 
> > > This means that if we set or negotiate a compatiblity mode, then
> > > hotplug a cpu, the hotplugged cpu doesn't get the right mode set and
> > > will incorrectly have the full native features.
> > > 
> > > To correct this, we set the compatibility mode on a cpu when it is
> > > brought online with the 'start-cpu' RTAS call.  Given that we no
> > > longer need to set the compatibility mode on all CPUs at machine
> > > reset, so we change that to only set the mode for the boot cpu.
> > > 
> > > Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
> > > ---
> > >  hw/ppc/spapr.c      | 2 +-
> > >  hw/ppc/spapr_rtas.c | 8 ++++++++
> > >  2 files changed, 9 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> > > index e22888ba06..d1acfe8858 100644
> > > --- a/hw/ppc/spapr.c
> > > +++ b/hw/ppc/spapr.c
> > > @@ -1510,7 +1510,7 @@ static void spapr_machine_reset(void)
> > >          spapr_ovec_cleanup(spapr->ov5_cas);
> > >          spapr->ov5_cas = spapr_ovec_new();
> > >  
> > > -        ppc_set_compat_all(spapr->max_compat_pvr, &error_fatal);
> > > +        ppc_set_compat(first_ppc_cpu, spapr->max_compat_pvr, &error_fatal);
> > >      }
> > >  
> > >      fdt = spapr_build_fdt(spapr, rtas_addr, spapr->rtas_size);
> > > diff --git a/hw/ppc/spapr_rtas.c b/hw/ppc/spapr_rtas.c
> > > index 4bb939d3d1..2ed00548c1 100644
> > > --- a/hw/ppc/spapr_rtas.c
> > > +++ b/hw/ppc/spapr_rtas.c
> > > @@ -163,6 +163,7 @@ static void rtas_start_cpu(PowerPCCPU *cpu_, sPAPRMachineState *spapr,
> > >          CPUState *cs = CPU(cpu);
> > >          CPUPPCState *env = &cpu->env;
> > >          PowerPCCPUClass *pcc = POWERPC_CPU_GET_CLASS(cpu);
> > > +        Error *local_err = NULL;
> > >  
> > >          if (!cs->halted) {
> > >              rtas_st(rets, 0, RTAS_OUT_HW_ERROR);
> > > @@ -174,6 +175,13 @@ static void rtas_start_cpu(PowerPCCPU *cpu_, sPAPRMachineState *spapr,
> > >           * new cpu enters */
> > >          kvm_cpu_synchronize_state(cs);
> > >  
> > > +        /* Set compatibility mode to match existing cpus */
> > > +        ppc_set_compat(cpu, POWERPC_CPU(first_cpu)->compat_pvr, &local_err);
> > 
> > Is it okay to report a simple HW error to the guest here instead of aborting
> > like we do with first_cpu at reset time ?
> 
> And if we don't opt for &error_fatal, we need an error_free() below.

Or better yet an error_report_err() which will display it and free
it.  I'll make that change.


> 
> > 
> > > +        if (local_err) {
> > > +            rtas_st(rets, 0, RTAS_OUT_HW_ERROR);
> > > +            return;
> > > +        }
> > > +
> > >          env->msr = (1ULL << MSR_SF) | (1ULL << MSR_ME);
> > >  
> > >          /* Enable Power-saving mode Exit Cause exceptions for the new CPU */
> > 
> 

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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Re: [Qemu-devel] [PATCH] spapr: Correct compatibility mode setting for hotplugged CPUs

[Greg Kurz]

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On Fri, 5 Jan 2018 14:07:29 +1100
David Gibson <david@gibson.dropbear.id.au> wrote:

> On Thu, Jan 04, 2018 at 06:47:18PM +0100, Greg Kurz wrote:
> > On Thu,  4 Jan 2018 15:24:05 +1100
> > David Gibson <david@gibson.dropbear.id.au> wrote:
> >   
> > > Currently the pseries machine sets the compatibility mode for the
> > > guest's cpus in two places: 1) at machine reset and 2) after CAS
> > > negotiation.
> > > 
> > > This means that if we set or negotiate a compatiblity mode, then
> > > hotplug a cpu, the hotplugged cpu doesn't get the right mode set and
> > > will incorrectly have the full native features.
> > > 
> > > To correct this, we set the compatibility mode on a cpu when it is
> > > brought online with the 'start-cpu' RTAS call.  Given that we no
> > > longer need to set the compatibility mode on all CPUs at machine
> > > reset, so we change that to only set the mode for the boot cpu.
> > > 
> > > Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
> > > ---
> > >  hw/ppc/spapr.c      | 2 +-
> > >  hw/ppc/spapr_rtas.c | 8 ++++++++
> > >  2 files changed, 9 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> > > index e22888ba06..d1acfe8858 100644
> > > --- a/hw/ppc/spapr.c
> > > +++ b/hw/ppc/spapr.c
> > > @@ -1510,7 +1510,7 @@ static void spapr_machine_reset(void)
> > >          spapr_ovec_cleanup(spapr->ov5_cas);
> > >          spapr->ov5_cas = spapr_ovec_new();
> > >  
> > > -        ppc_set_compat_all(spapr->max_compat_pvr, &error_fatal);
> > > +        ppc_set_compat(first_ppc_cpu, spapr->max_compat_pvr, &error_fatal);
> > >      }
> > >  
> > >      fdt = spapr_build_fdt(spapr, rtas_addr, spapr->rtas_size);
> > > diff --git a/hw/ppc/spapr_rtas.c b/hw/ppc/spapr_rtas.c
> > > index 4bb939d3d1..2ed00548c1 100644
> > > --- a/hw/ppc/spapr_rtas.c
> > > +++ b/hw/ppc/spapr_rtas.c
> > > @@ -163,6 +163,7 @@ static void rtas_start_cpu(PowerPCCPU *cpu_, sPAPRMachineState *spapr,
> > >          CPUState *cs = CPU(cpu);
> > >          CPUPPCState *env = &cpu->env;
> > >          PowerPCCPUClass *pcc = POWERPC_CPU_GET_CLASS(cpu);
> > > +        Error *local_err = NULL;
> > >  
> > >          if (!cs->halted) {
> > >              rtas_st(rets, 0, RTAS_OUT_HW_ERROR);
> > > @@ -174,6 +175,13 @@ static void rtas_start_cpu(PowerPCCPU *cpu_, sPAPRMachineState *spapr,
> > >           * new cpu enters */
> > >          kvm_cpu_synchronize_state(cs);
> > >  
> > > +        /* Set compatibility mode to match existing cpus */
> > > +        ppc_set_compat(cpu, POWERPC_CPU(first_cpu)->compat_pvr, &local_err);  
> > 
> > Is it okay to report a simple HW error to the guest here instead of aborting
> > like we do with first_cpu at reset time ?  
> 
> Should be: this happens before we turn the cpu on, so the effect will
> be that the guest fails to online the cpu.  That seems like a better
> failure mode than killing the already running guest.
> 

Of course, I generally agree with the "better failure mode". My point was
just that if we managed to set the compat mode with the first cpu but we
fail to propagate the same compat mode to subsequent cpus, then this is
a bug in QEMU or KVM.

> >   
> > > +        if (local_err) {
> > > +            rtas_st(rets, 0, RTAS_OUT_HW_ERROR);
> > > +            return;
> > > +        }
> > > +
> > >          env->msr = (1ULL << MSR_SF) | (1ULL << MSR_ME);
> > >  
> > >          /* Enable Power-saving mode Exit Cause exceptions for the new CPU */  
> >   
> 


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Re: [Qemu-devel] [PATCH] spapr: Correct compatibility mode setting for hotplugged CPUs

[David Gibson]

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On Thu, Jan 11, 2018 at 01:24:30PM +0100, Greg Kurz wrote:
> On Fri, 5 Jan 2018 14:07:29 +1100
> David Gibson <david@gibson.dropbear.id.au> wrote:
> 
> > On Thu, Jan 04, 2018 at 06:47:18PM +0100, Greg Kurz wrote:
> > > On Thu,  4 Jan 2018 15:24:05 +1100
> > > David Gibson <david@gibson.dropbear.id.au> wrote:
> > >   
> > > > Currently the pseries machine sets the compatibility mode for the
> > > > guest's cpus in two places: 1) at machine reset and 2) after CAS
> > > > negotiation.
> > > > 
> > > > This means that if we set or negotiate a compatiblity mode, then
> > > > hotplug a cpu, the hotplugged cpu doesn't get the right mode set and
> > > > will incorrectly have the full native features.
> > > > 
> > > > To correct this, we set the compatibility mode on a cpu when it is
> > > > brought online with the 'start-cpu' RTAS call.  Given that we no
> > > > longer need to set the compatibility mode on all CPUs at machine
> > > > reset, so we change that to only set the mode for the boot cpu.
> > > > 
> > > > Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
> > > > ---
> > > >  hw/ppc/spapr.c      | 2 +-
> > > >  hw/ppc/spapr_rtas.c | 8 ++++++++
> > > >  2 files changed, 9 insertions(+), 1 deletion(-)
> > > > 
> > > > diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> > > > index e22888ba06..d1acfe8858 100644
> > > > --- a/hw/ppc/spapr.c
> > > > +++ b/hw/ppc/spapr.c
> > > > @@ -1510,7 +1510,7 @@ static void spapr_machine_reset(void)
> > > >          spapr_ovec_cleanup(spapr->ov5_cas);
> > > >          spapr->ov5_cas = spapr_ovec_new();
> > > >  
> > > > -        ppc_set_compat_all(spapr->max_compat_pvr, &error_fatal);
> > > > +        ppc_set_compat(first_ppc_cpu, spapr->max_compat_pvr, &error_fatal);
> > > >      }
> > > >  
> > > >      fdt = spapr_build_fdt(spapr, rtas_addr, spapr->rtas_size);
> > > > diff --git a/hw/ppc/spapr_rtas.c b/hw/ppc/spapr_rtas.c
> > > > index 4bb939d3d1..2ed00548c1 100644
> > > > --- a/hw/ppc/spapr_rtas.c
> > > > +++ b/hw/ppc/spapr_rtas.c
> > > > @@ -163,6 +163,7 @@ static void rtas_start_cpu(PowerPCCPU *cpu_, sPAPRMachineState *spapr,
> > > >          CPUState *cs = CPU(cpu);
> > > >          CPUPPCState *env = &cpu->env;
> > > >          PowerPCCPUClass *pcc = POWERPC_CPU_GET_CLASS(cpu);
> > > > +        Error *local_err = NULL;
> > > >  
> > > >          if (!cs->halted) {
> > > >              rtas_st(rets, 0, RTAS_OUT_HW_ERROR);
> > > > @@ -174,6 +175,13 @@ static void rtas_start_cpu(PowerPCCPU *cpu_, sPAPRMachineState *spapr,
> > > >           * new cpu enters */
> > > >          kvm_cpu_synchronize_state(cs);
> > > >  
> > > > +        /* Set compatibility mode to match existing cpus */
> > > > +        ppc_set_compat(cpu, POWERPC_CPU(first_cpu)->compat_pvr, &local_err);  
> > > 
> > > Is it okay to report a simple HW error to the guest here instead of aborting
> > > like we do with first_cpu at reset time ?  
> > 
> > Should be: this happens before we turn the cpu on, so the effect will
> > be that the guest fails to online the cpu.  That seems like a better
> > failure mode than killing the already running guest.
> > 
> 
> Of course, I generally agree with the "better failure mode". My point was
> just that if we managed to set the compat mode with the first cpu but we
> fail to propagate the same compat mode to subsequent cpus, then this is
> a bug in QEMU or KVM.

Ah, I see your point.  Yes, I guess that's true.  Nonetheless, I think
the better failure mode is still a better idea, even if something goes
wrong elsewhere.

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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