[Qemu-devel] [PATCHv2] spapr: Correct compatibility mode setting for hotplugged CPUs

[Qemu-devel] [PATCHv2] 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>
Reviewed-by: Alexey Kardashevskiy <aik@ozlabs.ru>
---

Changes since v1:
 * Add an error_report_err() to display and free the error from
   ppc_set_compat() in rtas_start_cpu().
 

 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] [PATCHv2] spapr: Correct compatibility mode setting for hotplugged CPUs

[Greg Kurz]

On Fri,  5 Jan 2018 14:38:06 +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>
> Reviewed-by: Alexey Kardashevskiy <aik@ozlabs.ru>
> ---
> 
> Changes since v1:
>  * Add an error_report_err() to display and free the error from
>    ppc_set_compat() in rtas_start_cpu().
>  

It looks like this change wasn't committed when git-send-email was
invoked, and you missed Daniel's comment (typo in commit message)
and R-b...

> 
>  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) {

With a call to error_report_err() here, you can add:

Reviewed-by: Greg Kurz <groug@kaod.org>

> +            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] [PATCHv2] spapr: Correct compatibility mode setting for hotplugged CPUs

[satheesh rajendran]

On Fri, Jan 05, 2018 at 12:19:14PM +0100, Greg Kurz wrote:
> On Fri,  5 Jan 2018 14:38:06 +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>
> > Reviewed-by: Alexey Kardashevskiy <aik@ozlabs.ru>
> > ---

Tested in upstream with this patch and found fixed.
./ppc64-softmmu/qemu-system-ppc64 -M pseries,max-cpu-compat=power8,accel=kvm \
                                  -smp 1,cores=1,threads=1,sockets=1,maxcpus=2 \
                                  -m 2048 -nographic -enable-kvm /home/sath/images/hostos-ppc64le.qcow2 \
                                  -monitor stdio -serial /dev/pts/7
QEMU 2.11.50 monitor - type 'help' for more information
(qemu) device_add host-spapr-cpu-core,id=core1,core-id=1
(qemu) 

inside guest:
# taskset -c 1 ./a.out 
Illegal instruction


Reported-and-tested-by: Satheesh Rajendran <sathnaga@linux.vnet.ibm.com>

Regards,
-Satheesh


> > 
> > Changes since v1:
> >  * Add an error_report_err() to display and free the error from
> >    ppc_set_compat() in rtas_start_cpu().
> >  
> 
> It looks like this change wasn't committed when git-send-email was
> invoked, and you missed Daniel's comment (typo in commit message)
> and R-b...
> 
> > 
> >  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) {
> 
> With a call to error_report_err() here, you can add:
> 
> Reviewed-by: Greg Kurz <groug@kaod.org>
> 
> > +            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 */
> 
>