Re: [Qemu-devel] [PATCH] target-i386: do not read/write MSR_TSC_AUX from KVM if CPUID bit is not set

[Laszlo Ersek <lersek@redhat.com>]

On 03/30/16 22:59, Paolo Bonzini wrote:
> KVM does not let you read or write this MSR if the corresponding CPUID
> bit is not set.  This in turn causes MSRs that come after MSR_TSC_AUX
> to be ignored by KVM_SET_MRSS.

typo: KVM_SET_MRSS / KVM_SET_MSRS

Thanks for fixing this.
Laszlo

> 
> One visible symptom is that s3.flat from kvm-unit-tests fails with
> CPUs that do not have RDTSCP, because the SMBASE is not reset to
> 0x30000 after reset.
> 
> Fixes: c9b8f6b6210847b4381c5b2ee172b1c7eb9985d6
> Cc: qemu-stable@nongnu.org
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
>  target-i386/kvm.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/target-i386/kvm.c b/target-i386/kvm.c
> index 87ab969..19e2d94 100644
> --- a/target-i386/kvm.c
> +++ b/target-i386/kvm.c
> @@ -917,6 +917,9 @@ int kvm_arch_init_vcpu(CPUState *cs)
>      if (env->features[FEAT_1_EDX] & CPUID_MTRR) {
>          has_msr_mtrr = true;
>      }
> +    if (!(env->features[FEAT_8000_0001_EDX] & CPUID_EXT2_RDTSCP)) {
> +        has_msr_tsc_aux = false;
> +    }
>  
>      return 0;
>  }
>