Re: [PATCH v6 2/5] KVM: x86: Add IBPB support

[Jim Mattson]

On Thu, Feb 1, 2018 at 1:59 PM, KarimAllah Ahmed <karahmed@xxxxxxxxx> wrote:

> @@ -3684,6 +3696,22 @@ static int svm_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr)
>         case MSR_IA32_TSC:
>                 kvm_write_tsc(vcpu, msr);
>                 break;
> +       case MSR_IA32_PRED_CMD:
> +               if (!msr->host_initiated &&
> +                   !guest_cpuid_has(vcpu, X86_FEATURE_IBPB))
> +                       return 1;
> +
> +               if (data & ~PRED_CMD_IBPB)
> +                       return 1;
> +
> +               if (!data)
> +                       break;
> +
> +               wrmsrl(MSR_IA32_PRED_CMD, PRED_CMD_IBPB);

Should this be wrmsrl_safe? I don't see where we've verified host
support of this MSR.

> @@ -3342,6 +3369,34 @@ static int vmx_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
>         case MSR_IA32_TSC:
>                 kvm_write_tsc(vcpu, msr_info);
>                 break;
> +       case MSR_IA32_PRED_CMD:
> +               if (!msr_info->host_initiated &&
> +                   !guest_cpuid_has(vcpu, X86_FEATURE_IBPB) &&
> +                   !guest_cpuid_has(vcpu, X86_FEATURE_SPEC_CTRL))
> +                       return 1;
> +
> +               if (data & ~PRED_CMD_IBPB)
> +                       return 1;
> +
> +               if (!data)
> +                       break;
> +
> +               wrmsrl(MSR_IA32_PRED_CMD, PRED_CMD_IBPB);

And here too...wrmsrl_safe?