Re: [PATCH] pmu: prepare for migration support

[Gleb Natapov <gleb@redhat.com>]

On Thu, Mar 28, 2013 at 05:18:35PM +0100, Paolo Bonzini wrote:
> In order to migrate the PMU state correctly, we need to restore the
> values of MSR_CORE_PERF_GLOBAL_STATUS (a read-only register) and
> MSR_CORE_PERF_GLOBAL_OVF_CTRL (which has side effects when written).
> We also need to write the full 40-bit value of the performance counter,
> > which would only be possible with a v3 architectural PMU's
> > full-width counter MSRs.
> >
> > To distinguish host-initiated writes from the guest's, pass the
> > full struct msr_data to kvm_pmu_set_msr.
> 
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Applied, thanks.

> ---
>  arch/x86/include/asm/kvm_host.h |  2 +-
>  arch/x86/kvm/pmu.c              | 14 +++++++++++---
>  arch/x86/kvm/x86.c              |  4 ++--
>  3 files changed, 14 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index 36fba01..e2e09f3 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -1029,7 +1029,7 @@ void kvm_pmu_reset(struct kvm_vcpu *vcpu);
>  void kvm_pmu_cpuid_update(struct kvm_vcpu *vcpu);
>  bool kvm_pmu_msr(struct kvm_vcpu *vcpu, u32 msr);
>  int kvm_pmu_get_msr(struct kvm_vcpu *vcpu, u32 msr, u64 *data);
> -int kvm_pmu_set_msr(struct kvm_vcpu *vcpu, u32 msr, u64 data);
> +int kvm_pmu_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info);
>  int kvm_pmu_read_pmc(struct kvm_vcpu *vcpu, unsigned pmc, u64 *data);
>  void kvm_handle_pmu_event(struct kvm_vcpu *vcpu);
>  void kvm_deliver_pmi(struct kvm_vcpu *vcpu);
> diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c
> index cfc258a..c53e797 100644
> --- a/arch/x86/kvm/pmu.c
> +++ b/arch/x86/kvm/pmu.c
> @@ -360,10 +360,12 @@ int kvm_pmu_get_msr(struct kvm_vcpu *vcpu, u32 index, u64 *data)
>  	return 1;
>  }
>  
> -int kvm_pmu_set_msr(struct kvm_vcpu *vcpu, u32 index, u64 data)
> +int kvm_pmu_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
>  {
>  	struct kvm_pmu *pmu = &vcpu->arch.pmu;
>  	struct kvm_pmc *pmc;
> +	u32 index = msr_info->index;
> +	u64 data = msr_info->data;
>  
>  	switch (index) {
>  	case MSR_CORE_PERF_FIXED_CTR_CTRL:
> @@ -375,6 +377,10 @@ int kvm_pmu_set_msr(struct kvm_vcpu *vcpu, u32 index, u64 data)
>  		}
>  		break;
>  	case MSR_CORE_PERF_GLOBAL_STATUS:
> +		if (msr_info->host_initiated) {
> +			pmu->global_status = data;
> +			return 0;
> +		}
>  		break; /* RO MSR */
>  	case MSR_CORE_PERF_GLOBAL_CTRL:
>  		if (pmu->global_ctrl == data)
> @@ -386,7 +392,8 @@ int kvm_pmu_set_msr(struct kvm_vcpu *vcpu, u32 index, u64 data)
>  		break;
>  	case MSR_CORE_PERF_GLOBAL_OVF_CTRL:
>  		if (!(data & (pmu->global_ctrl_mask & ~(3ull<<62)))) {
> -			pmu->global_status &= ~data;
> +			if (!msr_info->host_initiated)
> +				pmu->global_status &= ~data;
>  			pmu->global_ovf_ctrl = data;
>  			return 0;
>  		}
> @@ -394,7 +401,8 @@ int kvm_pmu_set_msr(struct kvm_vcpu *vcpu, u32 index, u64 data)
>  	default:
>  		if ((pmc = get_gp_pmc(pmu, index, MSR_IA32_PERFCTR0)) ||
>  				(pmc = get_fixed_pmc(pmu, index))) {
> -			data = (s64)(s32)data;
> +			if (!msr_info->host_initiated)
> +				data = (s64)(s32)data;
>  			pmc->counter += data - read_pmc(pmc);
>  			return 0;
>  		} else if ((pmc = get_gp_pmc(pmu, index, MSR_P6_EVNTSEL0))) {
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 3e0a8ba..1d928af 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -2042,7 +2042,7 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
>  	case MSR_P6_EVNTSEL0:
>  	case MSR_P6_EVNTSEL1:
>  		if (kvm_pmu_msr(vcpu, msr))
> -			return kvm_pmu_set_msr(vcpu, msr, data);
> +			return kvm_pmu_set_msr(vcpu, msr_info);
>  
>  		if (pr || data != 0)
>  			vcpu_unimpl(vcpu, "disabled perfctr wrmsr: "
> @@ -2088,7 +2088,7 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
>  		if (msr && (msr == vcpu->kvm->arch.xen_hvm_config.msr))
>  			return xen_hvm_config(vcpu, data);
>  		if (kvm_pmu_msr(vcpu, msr))
> -			return kvm_pmu_set_msr(vcpu, msr, data);
> +			return kvm_pmu_set_msr(vcpu, msr_info);
>  		if (!ignore_msrs) {
>  			vcpu_unimpl(vcpu, "unhandled wrmsr: 0x%x data %llx\n",
>  				    msr, data);
> -- 
> 1.8.1.4

--
			Gleb.