linux-kernel - Re: [PATCH 1/2] KVM: vmx/pmu: Fix dummy check if lbr

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Date:   Tue, 23 Feb 2021 18:06:26 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Like Xu <like.xu@...ux.intel.com>,
        Sean Christopherson <seanjc@...gle.com>
Cc:     Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        x86@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] KVM: vmx/pmu: Fix dummy check if lbr_desc->event is
 created

On 23/02/21 02:39, Like Xu wrote:
> If lbr_desc->event is successfully created, the intel_pmu_create_
> guest_lbr_event() will return 0, otherwise it will return -ENOENT,
> and then jump to LBR msrs dummy handling.
> 
> Fixes: 1b5ac3226a1a ("KVM: vmx/pmu: Pass-through LBR msrs when the guest LBR event is ACTIVE")
> Signed-off-by: Like Xu <like.xu@...ux.intel.com>
> ---
>   arch/x86/kvm/vmx/pmu_intel.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kvm/vmx/pmu_intel.c b/arch/x86/kvm/vmx/pmu_intel.c
> index d1df618cb7de..d6a5fe19ff09 100644
> --- a/arch/x86/kvm/vmx/pmu_intel.c
> +++ b/arch/x86/kvm/vmx/pmu_intel.c
> @@ -320,7 +320,7 @@ static bool intel_pmu_handle_lbr_msrs_access(struct kvm_vcpu *vcpu,
>   	if (!intel_pmu_is_valid_lbr_msr(vcpu, index))
>   		return false;
>   
> -	if (!lbr_desc->event && !intel_pmu_create_guest_lbr_event(vcpu))
> +	if (!lbr_desc->event && intel_pmu_create_guest_lbr_event(vcpu))
>   		goto dummy;

Queued, adding a "< 0" to clarify the semantics of the function.

Paolo