RE: [PATCH v1 7/8] KVM: x86: Expose PEBS feature to guest

From: "Kang, Luwei" <luwei.kang@intel.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: "kvm@vger.kernel.org" <kvm@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"pbonzini@redhat.com" <pbonzini@redhat.com>,
	"rkrcmar@redhat.com" <rkrcmar@redhat.com>,
	"Christopherson, Sean J" <sean.j.christopherson@intel.com>,
	"vkuznets@redhat.com" <vkuznets@redhat.com>,
	"wanpengli@tencent.com" <wanpengli@tencent.com>,
	"jmattson@google.com" <jmattson@google.com>,
	"joro@8bytes.org" <joro@8bytes.org>,
	"tglx@linutronix.de" <tglx@linutronix.de>,
	"mingo@redhat.com" <mingo@redhat.com>,
	"bp@alien8.de" <bp@alien8.de>, "hpa@zytor.com" <hpa@zytor.com>,
	"x86@kernel.org" <x86@kernel.org>,
	"ak@linux.intel.com" <ak@linux.intel.com>,
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	"acme@kernel.org" <acme@kernel.org>,
	"mark.rutland@arm.com" <mark.rutland@arm.com>,
	"alexander.shishkin@linux.intel.com" 
	<alexander.shishkin@linux.intel.com>,
	"jolsa@redhat.com" <jolsa@redhat.com>,
	"namhyung@kernel.org" <namhyung@kernel.org>
Subject: RE: [PATCH v1 7/8] KVM: x86: Expose PEBS feature to guest
Date: Wed, 30 Oct 2019 04:07:03 +0000	[thread overview]
Message-ID: <82D7661F83C1A047AF7DC287873BF1E173835B45@SHSMSX104.ccr.corp.intel.com> (raw)
In-Reply-To: <20191029150531.GN4097@hirez.programming.kicks-ass.net>

> > Expose PEBS feature to guest by IA32_MISC_ENABLE[bit12].
> > IA32_MISC_ENABLE[bit12] is Processor Event Based Sampling (PEBS)
> > Unavailable (RO) flag:
> > 1 = PEBS is not supported; 0 = PEBS is supported.
> 
> Why does it make sense to expose this on SVM?

Thanks for the review. This patch won't expose the pebs feature to SVM and return not supported.

> 
> > Signed-off-by: Luwei Kang <luwei.kang@intel.com>
> > ---
> >  arch/x86/include/asm/kvm_host.h |  1 +
> >  arch/x86/kvm/svm.c              |  6 ++++++
> >  arch/x86/kvm/vmx/vmx.c          |  1 +
> >  arch/x86/kvm/x86.c              | 22 +++++++++++++++++-----
> >  4 files changed, 25 insertions(+), 5 deletions(-)
> >
> > diff --git a/arch/x86/include/asm/kvm_host.h
> > b/arch/x86/include/asm/kvm_host.h index 24a0ab9..76f5fa5 100644
> > --- a/arch/x86/include/asm/kvm_host.h
> > +++ b/arch/x86/include/asm/kvm_host.h
> > @@ -1127,6 +1127,7 @@ struct kvm_x86_ops {
> >  	bool (*xsaves_supported)(void);
> >  	bool (*umip_emulated)(void);
> >  	bool (*pt_supported)(void);
> > +	bool (*pebs_supported)(void);
> >  	bool (*pdcm_supported)(void);
> >
> >  	int (*check_nested_events)(struct kvm_vcpu *vcpu, bool
> > external_intr); diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
> > index 7e0a7b3..3a1bbb3 100644
> > --- a/arch/x86/kvm/svm.c
> > +++ b/arch/x86/kvm/svm.c
> > @@ -5975,6 +5975,11 @@ static bool svm_pt_supported(void)
> >  	return false;
> >  }
> >
> > +static bool svm_pebs_supported(void)
> > +{
> > +	return false;
> > +}
> > +
> >  static bool svm_pdcm_supported(void)
> >  {
> >  	return false;
> > @@ -7277,6 +7282,7 @@ static bool svm_apic_init_signal_blocked(struct kvm_vcpu *vcpu)
> >  	.xsaves_supported = svm_xsaves_supported,
> >  	.umip_emulated = svm_umip_emulated,
> >  	.pt_supported = svm_pt_supported,
> > +	.pebs_supported = svm_pebs_supported,
> >  	.pdcm_supported = svm_pdcm_supported,
> >
> >  	.set_supported_cpuid = svm_set_supported_cpuid, diff --git
> > a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index
> > 5c4dd05..3c370a3 100644
> > --- a/arch/x86/kvm/vmx/vmx.c
> > +++ b/arch/x86/kvm/vmx/vmx.c
> > @@ -7879,6 +7879,7 @@ static __exit void hardware_unsetup(void)
> >  	.xsaves_supported = vmx_xsaves_supported,
> >  	.umip_emulated = vmx_umip_emulated,
> >  	.pt_supported = vmx_pt_supported,
> > +	.pebs_supported = vmx_pebs_supported,
> >  	.pdcm_supported = vmx_pdcm_supported,
> >
> >  	.request_immediate_exit = vmx_request_immediate_exit, diff --git
> > a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 661e2bf..5f59073
> > 100644
> > --- a/arch/x86/kvm/x86.c
> > +++ b/arch/x86/kvm/x86.c
> > @@ -2591,6 +2591,7 @@ static void record_steal_time(struct kvm_vcpu
> > *vcpu)  int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data
> > *msr_info)  {
> >  	bool pr = false;
> > +	bool update_cpuid = false;
> >  	u32 msr = msr_info->index;
> >  	u64 data = msr_info->data;
> >
> > @@ -2671,11 +2672,17 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
> >  		    ((vcpu->arch.ia32_misc_enable_msr ^ data) & MSR_IA32_MISC_ENABLE_MWAIT)) {
> >  			if (!guest_cpuid_has(vcpu, X86_FEATURE_XMM3))
> >  				return 1;
> > -			vcpu->arch.ia32_misc_enable_msr = data;
> > -			kvm_update_cpuid(vcpu);
> > -		} else {
> > -			vcpu->arch.ia32_misc_enable_msr = data;
> > +			update_cpuid = true;
> >  		}
> > +
> > +		if (kvm_x86_ops->pebs_supported())
> > +			data &=  ~MSR_IA32_MISC_ENABLE_PEBS;
> 
> whitespace damage

Yes. Will fix it and below coding style violation.

Thanks,
Luwei Kang

> 
> > +		else
> > +			data |= MSR_IA32_MISC_ENABLE_PEBS;
> > +
> > +		vcpu->arch.ia32_misc_enable_msr = data;
> > +		if (update_cpuid)
> > +			kvm_update_cpuid(vcpu);
> >  		break;
> >  	case MSR_IA32_SMBASE:
> >  		if (!msr_info->host_initiated)
> > @@ -2971,7 +2978,12 @@ int kvm_get_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
> >  		msr_info->data = (u64)vcpu->arch.ia32_tsc_adjust_msr;
> >  		break;
> >  	case MSR_IA32_MISC_ENABLE:
> > -		msr_info->data = vcpu->arch.ia32_misc_enable_msr;
> > +		if (kvm_x86_ops->pebs_supported())
> > +			msr_info->data = (vcpu->arch.ia32_misc_enable_msr &
> > +						~MSR_IA32_MISC_ENABLE_PEBS);
> > +		else
> > +			msr_info->data = (vcpu->arch.ia32_misc_enable_msr |
> > +						MSR_IA32_MISC_ENABLE_PEBS);
> 
> Coding style violation.
> 
> >  		break;
> >  	case MSR_IA32_SMBASE:
> >  		if (!msr_info->host_initiated)
> > --
> > 1.8.3.1
> >