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

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Date:   Tue, 12 Jul 2022 14:49:08 +0300
From:   Maxim Levitsky <mlevitsk@...hat.com>
To:     Vitaly Kuznetsov <vkuznets@...hat.com>, kvm@...r.kernel.org,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>
Cc:     Anirudh Rayabharam <anrayabh@...ux.microsoft.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        linux-hyperv@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 01/25] KVM: x86: hyper-v: Expose access to debug MSRs
 in the partition privilege flags

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@...hat.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@...hat.com>

Best regards,
	Maxim Levitsky