Re: [Qemu-devel] [PULL 07/11] target-ppc: Fix CPU migration from qemu-2.6 <-> later versions

[Michael Roth <mdroth@linux.vnet.ibm.com>]

Quoting David Gibson (2016-11-22 23:10:09)
> On Wed, Nov 23, 2016 at 01:49:39PM +1100, David Gibson wrote:
> > When migration for target-ppc was converted to vmstate, several
> > VMSTATE_EQUAL() checks were foolishly included of things that really
> > should be internal state.  Specifically we verified equality of the
> > insns_flags and insns_flags2 fields, which are used within TCG to
> > determine which groups of instructions are available on this cpu
> > model.  Between qemu-2.6 and qemu-2.7 we made some changes to these
> > classes which broke migration.
> > 
> > This path fixes migration both forwards and backwards.  On migration
> > from 2.6 to later versions we import the fields into teporary
> > variables, which we then ignore.  In migration backwards, we populate
> > the temporary fields from the runtime fields, but mask out the bits
> > which were added after qemu-2.6, allowing the VMSTATE_EQUAL in
> > qemu-2.6 to accept the stream.
> 
> Mike,
> 
> This patch (alone) should also be applied to the v2.7 stable branch to
> fix the v2.6<->v2.7 migration failure.  When I tried yesterday the
> patch applied clean to v2.7.0, so it shouldn't need reworking.
> 
> Would you like me to resend specifically for the stable branch, or are
> you happy to just pick it up from here?

I can pick it up from here.

> 
> > 
> > Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
> > Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> > Reviewed-by: Thomas Huth <thuth@redhat.com>
> > Reviewed-by: Greg Kurz <groug@kaod.org>
> > ---
> >  target-ppc/cpu.h     |  6 ++++++
> >  target-ppc/machine.c | 29 +++++++++++++++++++++++++----
> >  2 files changed, 31 insertions(+), 4 deletions(-)
> > 
> > diff --git a/target-ppc/cpu.h b/target-ppc/cpu.h
> > index 1c90adb..7798b2e 100644
> > --- a/target-ppc/cpu.h
> > +++ b/target-ppc/cpu.h
> > @@ -1166,6 +1166,12 @@ struct PowerPCCPU {
> >      int cpu_dt_id;
> >      uint32_t max_compat;
> >      uint32_t cpu_version;
> > +
> > +    /* fields used only during migration for compatibility hacks */
> > +    target_ulong mig_msr_mask;
> > +    uint64_t mig_insns_flags;
> > +    uint64_t mig_insns_flags2;
> > +    uint32_t mig_nb_BATs;
> >  };
> >  
> >  static inline PowerPCCPU *ppc_env_get_cpu(CPUPPCState *env)
> > diff --git a/target-ppc/machine.c b/target-ppc/machine.c
> > index e43cb6c..fcac263 100644
> > --- a/target-ppc/machine.c
> > +++ b/target-ppc/machine.c
> > @@ -140,6 +140,21 @@ static void cpu_pre_save(void *opaque)
> >      PowerPCCPU *cpu = opaque;
> >      CPUPPCState *env = &cpu->env;
> >      int i;
> > +    uint64_t insns_compat_mask =
> > +        PPC_INSNS_BASE | PPC_ISEL | PPC_STRING | PPC_MFTB
> > +        | PPC_FLOAT | PPC_FLOAT_FSEL | PPC_FLOAT_FRES
> > +        | PPC_FLOAT_FSQRT | PPC_FLOAT_FRSQRTE | PPC_FLOAT_FRSQRTES
> > +        | PPC_FLOAT_STFIWX | PPC_FLOAT_EXT
> > +        | PPC_CACHE | PPC_CACHE_ICBI | PPC_CACHE_DCBZ
> > +        | PPC_MEM_SYNC | PPC_MEM_EIEIO | PPC_MEM_TLBIE | PPC_MEM_TLBSYNC
> > +        | PPC_64B | PPC_64BX | PPC_ALTIVEC
> > +        | PPC_SEGMENT_64B | PPC_SLBI | PPC_POPCNTB | PPC_POPCNTWD;
> > +    uint64_t insns_compat_mask2 = PPC2_VSX | PPC2_VSX207 | PPC2_DFP | PPC2_DBRX
> > +        | PPC2_PERM_ISA206 | PPC2_DIVE_ISA206
> > +        | PPC2_ATOMIC_ISA206 | PPC2_FP_CVT_ISA206
> > +        | PPC2_FP_TST_ISA206 | PPC2_BCTAR_ISA207
> > +        | PPC2_LSQ_ISA207 | PPC2_ALTIVEC_207
> > +        | PPC2_ISA205 | PPC2_ISA207S | PPC2_FP_CVT_S64 | PPC2_TM;
> >  
> >      env->spr[SPR_LR] = env->lr;
> >      env->spr[SPR_CTR] = env->ctr;
> > @@ -161,6 +176,12 @@ static void cpu_pre_save(void *opaque)
> >          env->spr[SPR_IBAT4U + 2*i] = env->IBAT[0][i+4];
> >          env->spr[SPR_IBAT4U + 2*i + 1] = env->IBAT[1][i+4];
> >      }
> > +
> > +    /* Hacks for migration compatibility between 2.6, 2.7 & 2.8 */
> > +    cpu->mig_msr_mask = env->msr_mask;
> > +    cpu->mig_insns_flags = env->insns_flags & insns_compat_mask;
> > +    cpu->mig_insns_flags2 = env->insns_flags2 & insns_compat_mask2;
> > +    cpu->mig_nb_BATs = env->nb_BATs;
> >  }
> >  
> >  static int cpu_post_load(void *opaque, int version_id)
> > @@ -561,10 +582,10 @@ const VMStateDescription vmstate_ppc_cpu = {
> >          /* FIXME: access_type? */
> >  
> >          /* Sanity checking */
> > -        VMSTATE_UINTTL_EQUAL(env.msr_mask, PowerPCCPU),
> > -        VMSTATE_UINT64_EQUAL(env.insns_flags, PowerPCCPU),
> > -        VMSTATE_UINT64_EQUAL(env.insns_flags2, PowerPCCPU),
> > -        VMSTATE_UINT32_EQUAL(env.nb_BATs, PowerPCCPU),
> > +        VMSTATE_UINTTL(mig_msr_mask, PowerPCCPU),
> > +        VMSTATE_UINT64(mig_insns_flags, PowerPCCPU),
> > +        VMSTATE_UINT64(mig_insns_flags2, PowerPCCPU),
> > +        VMSTATE_UINT32(mig_nb_BATs, PowerPCCPU),
> >          VMSTATE_END_OF_LIST()
> >      },
> >      .subsections = (const VMStateDescription*[]) {
> 
> -- 
> 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