Re: [PATCH v2 3/3] KVM: SVM: add migration support for nested TSC scaling

[Paolo Bonzini <pbonzini@redhat.com>]

On 01/11/21 14:23, Maxim Levitsky wrote:
> Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
> ---
>   target/i386/cpu.c     |  5 +++++
>   target/i386/cpu.h     |  4 ++++
>   target/i386/kvm/kvm.c | 15 +++++++++++++++
>   target/i386/machine.c | 23 +++++++++++++++++++++++
>   4 files changed, 47 insertions(+)

It's easier to migrate it unconditionally:

diff --git a/target/i386/machine.c b/target/i386/machine.c
index e1138693f3..83c2b91529 100644
--- a/target/i386/machine.c
+++ b/target/i386/machine.c
@@ -1286,8 +1286,7 @@ static bool amd_tsc_scale_msr_needed(void *opaque)
      X86CPU *cpu = opaque;
      CPUX86State *env = &cpu->env;

-    return env->amd_tsc_scale_msr &&
-           env->amd_tsc_scale_msr != MSR_AMD64_TSC_RATIO_DEFAULT;
+    return (env->features[FEAT_SVM] & CPUID_SVM_TSCSCALE);
  }

  static const VMStateDescription amd_tsc_scale_msr_ctrl = {

> +    if (env->features[FEAT_SVM] & CPUID_SVM_TSCSCALE) {
> +        env->amd_tsc_scale_msr =  MSR_AMD64_TSC_RATIO_DEFAULT;
> +    }

and also set it unconditionally here, so that it's always passed 
correctly to KVM.

I queued patches 2 and 3, for (1) I need to think more about migration 
to older QEMU versions.

Paolo