Re: [Qemu-devel] [Qemu-ppc] [PATCH] spapr/ppc: fix backward migration to QEMU 2.9

[Greg Kurz]

On Tue, 20 Jun 2017 15:08:47 +0200
Laurent Vivier <address@hidden> wrote:

> On 19/06/2017 19:05, Greg Kurz wrote:
> > Commit c783b0012708 ("ppc: Rework CPU compatibility testing across
> > migration") added a subsection to the vmstate description of CPUs.
> > This subsection is sent when the CPU compat_pvr field is non-zero,
> > which is likely to happen after CAS negociation (since QEMU 2.9) or
> > even before CAS negociation if the user explicitely asked for compat
> > mode.
> > 
> > This breaks backward migration of existing pseries-2.9 machine types
> > since they don't know about this "compat" subsection:
> > 
> > qemu-system-ppc64: error while loading state for instance 0x0 of
> >  device 'cpu'
> > 
> > This patch reverts to the behavior of simply ignoring the PVR when
> > migrating older machines (ie, let the migration succeed if the user
> > is sure that the CPU on the destination is close enough to work).
> > 
> > Signed-off-by: Greg Kurz <address@hidden>  
> 
> Reviewed-by: Laurent Vivier <address@hidden>
> 
> but I think it should be merged with patch ("ppc: Rework CPU
> compatibility testing across migration") that is not merged and in the
> maintainer tree.
> 

I agree this would be better for bisect.

Cheers,

--
Greg

> thanks,
> Laurent
> 
> > ---
> >  hw/ppc/spapr.c              |    7 ++++++-
> >  target/ppc/cpu.h            |    1 +
> >  target/ppc/machine.c        |    2 +-
> >  target/ppc/translate_init.c |    2 ++
> >  4 files changed, 10 insertions(+), 2 deletions(-)
> > 
> > diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> > index d4d781876b27..265d49bbcd7f 100644
> > --- a/hw/ppc/spapr.c
> > +++ b/hw/ppc/spapr.c
> > @@ -3474,7 +3474,12 @@ DEFINE_SPAPR_MACHINE(2_10, "2.10", true);
> >   * pseries-2.9
> >   */
> >  #define SPAPR_COMPAT_2_9                                               \
> > -    HW_COMPAT_2_9
> > +    HW_COMPAT_2_9                                                      \
> > +    {                                                                  \
> > +        .driver = TYPE_POWERPC_CPU,                                    \
> > +        .property = "pre-2.10-migration",                              \
> > +        .value    = "on",                                              \
> > +    },                                                                 \
> >  
> >  static void spapr_machine_2_9_instance_options(MachineState *machine)
> >  {
> > diff --git a/target/ppc/cpu.h b/target/ppc/cpu.h
> > index 09393e601fd9..6ee2a26a963d 100644
> > --- a/target/ppc/cpu.h
> > +++ b/target/ppc/cpu.h
> > @@ -1211,6 +1211,7 @@ struct PowerPCCPU {
> >      uint64_t mig_insns_flags;
> >      uint64_t mig_insns_flags2;
> >      uint32_t mig_nb_BATs;
> > +    bool pre_2_10_migration;
> >  };
> >  
> >  static inline PowerPCCPU *ppc_env_get_cpu(CPUPPCState *env)
> > diff --git a/target/ppc/machine.c b/target/ppc/machine.c
> > index a29aabe8f079..1b7aede579ea 100644
> > --- a/target/ppc/machine.c
> > +++ b/target/ppc/machine.c
> > @@ -608,7 +608,7 @@ static bool compat_needed(void *opaque)
> >      PowerPCCPU *cpu = opaque;
> >  
> >      assert(!(cpu->compat_pvr && !cpu->vhyp));
> > -    return (cpu->compat_pvr != 0);
> > +    return !cpu->pre_2_10_migration && cpu->compat_pvr != 0;
> >  }
> >  
> >  static const VMStateDescription vmstate_compat = {
> > diff --git a/target/ppc/translate_init.c b/target/ppc/translate_init.c
> > index 53aff5a7b734..783bf98217cc 100644
> > --- a/target/ppc/translate_init.c
> > +++ b/target/ppc/translate_init.c
> > @@ -10610,6 +10610,8 @@ static gchar *ppc_gdb_arch_name(CPUState *cs)
> >  
> >  static Property ppc_cpu_properties[] = {
> >      DEFINE_PROP_BOOL("pre-2.8-migration", PowerPCCPU, pre_2_8_migration, 
> > false),
> > +    DEFINE_PROP_BOOL("pre-2.10-migration", PowerPCCPU, pre_2_10_migration,
> > +                     false),
> >      DEFINE_PROP_END_OF_LIST(),
> >  };
> >  
> > 
> >   
>

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