Re: [Qemu-devel] [PATCH] migration: savevm: consult migration blockers

[Dr. David Alan Gilbert]

* Paolo Bonzini (address@hidden) wrote:
> There is really no difference between live migration and savevm, except
> that savevm does not require bdrv_invalidate_cache to be implemented
> by all disks.  However, it is unlikely that savevm is used with anything
> except qcow2 disks, so the penalty is small and worth the improvement
> in catching bad usage of savevm.
> 
> Only one place was taking care of savevm when adding a migration blocker,
> and it can be removed.

OK, I'm not sure if it was actually a split between savevm and migration
or just that the migration blockers were added later.

> Signed-off-by: Paolo Bonzini <address@hidden>
> ---
>  migration/savevm.c | 4 ++++
>  target/i386/kvm.c  | 3 ---
>  2 files changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/migration/savevm.c b/migration/savevm.c
> index ef707b8c43..1c49776a91 100644
> --- a/migration/savevm.c
> +++ b/migration/savevm.c
> @@ -2455,6 +2455,10 @@ int save_snapshot(const char *name, Error **errp)
>      struct tm tm;
>      AioContext *aio_context;
>  
> +    if (migration_is_blocked(errp)) {
> +        return false;
> +    }
> +
>      if (!replay_can_snapshot()) {
>          error_setg(errp, "Record/replay does not allow making snapshot "
>                     "right now. Try once more later.");
> diff --git a/target/i386/kvm.c b/target/i386/kvm.c
> index 3b6fbd3f20..d222b68fe4 100644
> --- a/target/i386/kvm.c
> +++ b/target/i386/kvm.c
> @@ -1284,7 +1284,6 @@ int kvm_arch_init_vcpu(CPUState *cs)
>      if (!env->user_tsc_khz) {
>          if ((env->features[FEAT_8000_0007_EDX] & CPUID_APM_INVTSC) &&
>              invtsc_mig_blocker == NULL) {
> -            /* for migration */
>              error_setg(&invtsc_mig_blocker,
>                         "State blocked by non-migratable CPU device"
>                         " (invtsc flag)");
> @@ -1294,8 +1293,6 @@ int kvm_arch_init_vcpu(CPUState *cs)
>                  error_free(invtsc_mig_blocker);
>                  return r;
>              }
> -            /* for savevm */
> -            vmstate_x86_cpu.unmigratable = 1;

So that means vmstate_x86_cpu can be static now - but why does it live
in machine.c rather than cpu.c ?

Dave

>          }
>      }
>  
> -- 
> 2.19.1
> 
> 
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK