linux-kernel - Re: [PATCH 4/4] kvm: Implement PEBS virtualization

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Date:	Tue, 10 Jun 2014 15:04:48 -0300
From:	Marcelo Tosatti <mtosatti@...hat.com>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	peterz@...radead.org, gleb@...nel.org, pbonzini@...hat.com,
	eranian@...gle.com, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org, Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCH 4/4] kvm: Implement PEBS virtualization

On Thu, May 29, 2014 at 06:12:07PM -0700, Andi Kleen wrote:
>  {
>  	struct kvm_pmu *pmu = &vcpu->arch.pmu;
> @@ -407,6 +551,20 @@ int kvm_pmu_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
>  			return 0;
>  		}
>  		break;
> +	case MSR_IA32_DS_AREA:
> +		pmu->ds_area = data;
> +		return 0;
> +	case MSR_IA32_PEBS_ENABLE:
> +		if (data & ~0xf0000000fULL)
> +			break;

Bit 63 == PS_ENABLE ?

>  void kvm_handle_pmu_event(struct kvm_vcpu *vcpu)
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index 33e8c02..4f39917 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -7288,6 +7288,12 @@ static void __noclone vmx_vcpu_run(struct kvm_vcpu *vcpu)
>  	atomic_switch_perf_msrs(vmx);
>  	debugctlmsr = get_debugctlmsr();
>  
> +	/* Move this somewhere else? */

Unless you hook into vcpu->arch.pmu.ds_area and perf_get_ds_area()
writers, it has to be at every vcpu entry.

Could compare values in MSR save area to avoid switch.

> +	if (vcpu->arch.pmu.ds_area)
> +		add_atomic_switch_msr(vmx, MSR_IA32_DS_AREA,
> +				      vcpu->arch.pmu.ds_area,
> +				      perf_get_ds_area());

Should clear_atomic_switch_msr before 
add_atomic_switch_msr.

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