linux-kernel - [PATCH v12 12/17] KVM: x86: Set PEBS_UNAVAIL in IA32_MISC

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Date:   Fri,  4 Mar 2022 17:04:22 +0800
From:   Like Xu <like.xu.linux@...il.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Sean Christopherson <seanjc@...gle.com>,
        Jim Mattson <jmattson@...gle.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        x86@...nel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v12 12/17] KVM: x86: Set PEBS_UNAVAIL in IA32_MISC_ENABLE when PEBS is enabled

From: Like Xu <like.xu@...ux.intel.com>

The bit 12 represents "Processor Event Based Sampling Unavailable (RO)" :
	1 = PEBS is not supported.
	0 = PEBS is supported.

A write to this PEBS_UNAVL available bit will bring #GP(0) when guest PEBS
is enabled. Some PEBS drivers in guest may care about this bit.

Signed-off-by: Like Xu <like.xu@...ux.intel.com>
---
 arch/x86/kvm/vmx/pmu_intel.c | 2 ++
 arch/x86/kvm/x86.c           | 8 +++++++-
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/vmx/pmu_intel.c b/arch/x86/kvm/vmx/pmu_intel.c
index 3cfc90d5c4f4..a1fadfa3fbec 100644
--- a/arch/x86/kvm/vmx/pmu_intel.c
+++ b/arch/x86/kvm/vmx/pmu_intel.c
@@ -601,6 +601,7 @@ static void intel_pmu_refresh(struct kvm_vcpu *vcpu)
 		bitmap_set(pmu->all_valid_pmc_idx, INTEL_PMC_IDX_FIXED_VLBR, 1);
 
 	if (vcpu->arch.perf_capabilities & PERF_CAP_PEBS_FORMAT) {
+		vcpu->arch.ia32_misc_enable_msr &= ~MSR_IA32_MISC_ENABLE_PEBS_UNAVAIL;
 		if (vcpu->arch.perf_capabilities & PERF_CAP_PEBS_BASELINE) {
 			pmu->pebs_enable_mask = ~pmu->global_ctrl;
 			pmu->reserved_bits &= ~ICL_EVENTSEL_ADAPTIVE;
@@ -614,6 +615,7 @@ static void intel_pmu_refresh(struct kvm_vcpu *vcpu)
 				~((1ull << pmu->nr_arch_gp_counters) - 1);
 		}
 	} else {
+		vcpu->arch.ia32_misc_enable_msr |= MSR_IA32_MISC_ENABLE_PEBS_UNAVAIL;
 		vcpu->arch.perf_capabilities &= ~PERF_CAP_PEBS_MASK;
 	}
 }
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 3c7a51468216..41b25412bad4 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3517,7 +3517,13 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 		break;
 	case MSR_IA32_MISC_ENABLE: {
 		u64 old_val = vcpu->arch.ia32_misc_enable_msr;
-		u64 pmu_mask = MSR_IA32_MISC_ENABLE_EMON;
+		u64 pmu_mask = MSR_IA32_MISC_ENABLE_EMON |
+			MSR_IA32_MISC_ENABLE_PEBS_UNAVAIL;
+
+		/* RO bits */
+		if (!msr_info->host_initiated &&
+		    ((old_val ^ data) & MSR_IA32_MISC_ENABLE_PEBS_UNAVAIL))
+			return 1;
 
 		/*
 		 * For a dummy user space, the order of setting vPMU capabilities and
-- 
2.35.1