Re: [PATCH v3 01/25] KVM: x86: hyper-v: Expose access to debug MSRs in the partition privilege flags

Maxim Levitsky
2022-07-12T11:49:19Z

On Fri, 2022-07-08 at 16:41 +0200, Vitaly Kuznetsov wrote:
> For some features, Hyper-V spec defines two separate CPUID bits: one
> listing whether the feature is supported or not and another one showing
> whether guest partition was granted access to the feature ("partition
> privilege mask"). 'Debug MSRs available' is one of such features. Add
> the missing 'access' bit.
>
> Fixes: f97f5a56f597 ("x86/kvm/hyper-v: Add support for synthetic debugger interface")
> Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
> ---
> arch/x86/kvm/hyperv.c | 1 +
> include/asm-generic/hyperv-tlfs.h | 2 ++
> 2 files changed, 3 insertions(+)
>
> diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
> index e2e95a6fccfd..e08189211d9a 100644
> --- a/arch/x86/kvm/hyperv.c
> +++ b/arch/x86/kvm/hyperv.c
> @@ -2496,6 +2496,7 @@ int kvm_get_hv_cpuid(struct kvm_vcpu *vcpu, struct kvm_cpuid2 *cpuid,
> ent->eax |= HV_MSR_RESET_AVAILABLE;
> ent->eax |= HV_MSR_REFERENCE_TSC_AVAILABLE;
> ent->eax |= HV_ACCESS_FREQUENCY_MSRS;
> + ent->eax |= HV_ACCESS_DEBUG_MSRS;
> ent->eax |= HV_ACCESS_REENLIGHTENMENT;
>
> ent->ebx |= HV_POST_MESSAGES;
> diff --git a/include/asm-generic/hyperv-tlfs.h b/include/asm-generic/hyperv-tlfs.h
> index fdce7a4cfc6f..1d99dd296a76 100644
> --- a/include/asm-generic/hyperv-tlfs.h
> +++ b/include/asm-generic/hyperv-tlfs.h
> @@ -70,6 +70,8 @@
> #define HV_MSR_GUEST_IDLE_AVAILABLE BIT(10)
> /* Partition local APIC and TSC frequency registers available */
> #define HV_ACCESS_FREQUENCY_MSRS BIT(11)
> +/* Debug MSRs available */
> +#define HV_ACCESS_DEBUG_MSRS BIT(12)
> /* AccessReenlightenmentControls privilege */
> #define HV_ACCESS_REENLIGHTENMENT BIT(13)
> /* AccessTscInvariantControls privilege */

I guess you mean HV_FEATURE_DEBUG_MSRS_AVAILABLE and the new HV_ACCESS_DEBUG_MSRS

I checked the spec and the bits match, so I guess:

Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>

Best regards,
Maxim Levitsky