diff mbox series

[v4,20/38] KVM: x86/pmu: Check if mediated vPMU can intercept rdpmc

Message ID 20250324173121.1275209-21-mizhang@google.com (mailing list archive)
State New
Headers show
Series Mediated vPMU 4.0 for x86 | expand

Commit Message

Mingwei Zhang March 24, 2025, 5:31 p.m. UTC 
From: Dapeng Mi <dapeng1.mi@linux.intel.com>

Check if rdpmc can be intercepted for mediated vPMU. Simply speaking,
if guest own all PMU counters in mediated vPMU, then rdpmc interception
should be disabled to mitigate the performance impact, otherwise rdpmc
has to be intercepted to avoid guest obtain host counter's data via
rdpmc instruction.

Co-developed-by: Mingwei Zhang <mizhang@google.com>
Signed-off-by: Mingwei Zhang <mizhang@google.com>
Co-developed-by: Sandipan Das <sandipan.das@amd.com>
Signed-off-by: Sandipan Das <sandipan.das@amd.com>
Signed-off-by: Dapeng Mi <dapeng1.mi@linux.intel.com>
---
 arch/x86/include/asm/msr-index.h |  1 +
 arch/x86/kvm/pmu.c               | 34 ++++++++++++++++++++++++++++++++
 arch/x86/kvm/pmu.h               | 19 ++++++++++++++++++
 arch/x86/kvm/svm/pmu.c           | 14 ++++++++++++-
 arch/x86/kvm/vmx/pmu_intel.c     | 18 ++++++++---------
 5 files changed, 76 insertions(+), 10 deletions(-)
diff mbox series

Patch

diff --git a/arch/x86/include/asm/msr-index.h b/arch/x86/include/asm/msr-index.h
index ca70846ffd55..337f4b0a2998 100644
--- a/arch/x86/include/asm/msr-index.h
+++ b/arch/x86/include/asm/msr-index.h
@@ -312,6 +312,7 @@ 
 #define PERF_CAP_PEBS_FORMAT		0xf00
 #define PERF_CAP_FW_WRITES		BIT_ULL(13)
 #define PERF_CAP_PEBS_BASELINE		BIT_ULL(14)
+#define PERF_CAP_PERF_METRICS		BIT_ULL(15)
 #define PERF_CAP_PEBS_MASK		(PERF_CAP_PEBS_TRAP | PERF_CAP_ARCH_REG | \
 					 PERF_CAP_PEBS_FORMAT | PERF_CAP_PEBS_BASELINE)
 
diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c
index 92c742ead663..6ad71752be4b 100644
--- a/arch/x86/kvm/pmu.c
+++ b/arch/x86/kvm/pmu.c
@@ -604,6 +604,40 @@  int kvm_pmu_rdpmc(struct kvm_vcpu *vcpu, unsigned idx, u64 *data)
 	return 0;
 }
 
+inline bool kvm_rdpmc_in_guest(struct kvm_vcpu *vcpu)
+{
+	struct kvm_pmu *pmu = vcpu_to_pmu(vcpu);
+
+	if (!kvm_mediated_pmu_enabled(vcpu))
+		return false;
+
+	/*
+	 * VMware allows access to these Pseduo-PMCs even when read via RDPMC
+	 * in Ring3 when CR4.PCE=0.
+	 */
+	if (enable_vmware_backdoor)
+		return false;
+
+	/*
+	 * FIXME: In theory, perf metrics is always combined with fixed
+	 *	  counter 3. it's fair enough to compare the guest and host
+	 *	  fixed counter number and don't need to check perf metrics
+	 *	  explicitly. However kvm_pmu_cap.num_counters_fixed is limited
+	 *	  KVM_MAX_NR_FIXED_COUNTERS (3) as fixed counter 3 is not
+	 *	  supported now. perf metrics is still needed to be checked
+	 *	  explicitly here. Once fixed counter 3 is supported, the perf
+	 *	  metrics checking can be removed.
+	 */
+	return pmu->nr_arch_gp_counters == kvm_pmu_cap.num_counters_gp &&
+	       pmu->nr_arch_fixed_counters == kvm_pmu_cap.num_counters_fixed &&
+	       vcpu_has_perf_metrics(vcpu) == kvm_host_has_perf_metrics() &&
+	       pmu->counter_bitmask[KVM_PMC_GP] ==
+				(BIT_ULL(kvm_pmu_cap.bit_width_gp) - 1) &&
+	       pmu->counter_bitmask[KVM_PMC_FIXED] ==
+				(BIT_ULL(kvm_pmu_cap.bit_width_fixed) - 1);
+}
+EXPORT_SYMBOL_GPL(kvm_rdpmc_in_guest);
+
 void kvm_pmu_deliver_pmi(struct kvm_vcpu *vcpu)
 {
 	if (lapic_in_kernel(vcpu)) {
diff --git a/arch/x86/kvm/pmu.h b/arch/x86/kvm/pmu.h
index e1d0096f249b..509c995b7871 100644
--- a/arch/x86/kvm/pmu.h
+++ b/arch/x86/kvm/pmu.h
@@ -271,6 +271,24 @@  static inline bool pmc_is_globally_enabled(struct kvm_pmc *pmc)
 	return test_bit(pmc->idx, (unsigned long *)&pmu->global_ctrl);
 }
 
+static inline u64 vcpu_get_perf_capabilities(struct kvm_vcpu *vcpu)
+{
+	if (!guest_cpu_cap_has(vcpu, X86_FEATURE_PDCM))
+		return 0;
+
+	return vcpu->arch.perf_capabilities;
+}
+
+static inline bool vcpu_has_perf_metrics(struct kvm_vcpu *vcpu)
+{
+	return !!(vcpu_get_perf_capabilities(vcpu) & PERF_CAP_PERF_METRICS);
+}
+
+static inline bool kvm_host_has_perf_metrics(void)
+{
+	return !!(kvm_host.perf_capabilities & PERF_CAP_PERF_METRICS);
+}
+
 void kvm_pmu_deliver_pmi(struct kvm_vcpu *vcpu);
 void kvm_pmu_handle_event(struct kvm_vcpu *vcpu);
 int kvm_pmu_rdpmc(struct kvm_vcpu *vcpu, unsigned pmc, u64 *data);
@@ -287,6 +305,7 @@  void kvm_pmu_trigger_event(struct kvm_vcpu *vcpu, u64 eventsel);
 bool vcpu_pmu_can_enable(struct kvm_vcpu *vcpu);
 
 bool is_vmware_backdoor_pmc(u32 pmc_idx);
+bool kvm_rdpmc_in_guest(struct kvm_vcpu *vcpu);
 
 extern struct kvm_pmu_ops intel_pmu_ops;
 extern struct kvm_pmu_ops amd_pmu_ops;
diff --git a/arch/x86/kvm/svm/pmu.c b/arch/x86/kvm/svm/pmu.c
index c8b9fd9b5350..153972e944eb 100644
--- a/arch/x86/kvm/svm/pmu.c
+++ b/arch/x86/kvm/svm/pmu.c
@@ -173,7 +173,7 @@  static int amd_pmu_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 	return 1;
 }
 
-static void amd_pmu_refresh(struct kvm_vcpu *vcpu)
+static void __amd_pmu_refresh(struct kvm_vcpu *vcpu)
 {
 	struct kvm_pmu *pmu = vcpu_to_pmu(vcpu);
 	union cpuid_0x80000022_ebx ebx;
@@ -212,6 +212,18 @@  static void amd_pmu_refresh(struct kvm_vcpu *vcpu)
 	bitmap_set(pmu->all_valid_pmc_idx, 0, pmu->nr_arch_gp_counters);
 }
 
+static void amd_pmu_refresh(struct kvm_vcpu *vcpu)
+{
+	struct vcpu_svm *svm = to_svm(vcpu);
+
+	__amd_pmu_refresh(vcpu);
+
+	if (kvm_rdpmc_in_guest(vcpu))
+		svm_clr_intercept(svm, INTERCEPT_RDPMC);
+	else
+		svm_set_intercept(svm, INTERCEPT_RDPMC);
+}
+
 static void amd_pmu_init(struct kvm_vcpu *vcpu)
 {
 	struct kvm_pmu *pmu = vcpu_to_pmu(vcpu);
diff --git a/arch/x86/kvm/vmx/pmu_intel.c b/arch/x86/kvm/vmx/pmu_intel.c
index fc017e9a6a0c..2a5f79206b02 100644
--- a/arch/x86/kvm/vmx/pmu_intel.c
+++ b/arch/x86/kvm/vmx/pmu_intel.c
@@ -108,14 +108,6 @@  static struct kvm_pmc *intel_rdpmc_ecx_to_pmc(struct kvm_vcpu *vcpu,
 	return &counters[array_index_nospec(idx, num_counters)];
 }
 
-static inline u64 vcpu_get_perf_capabilities(struct kvm_vcpu *vcpu)
-{
-	if (!guest_cpu_cap_has(vcpu, X86_FEATURE_PDCM))
-		return 0;
-
-	return vcpu->arch.perf_capabilities;
-}
-
 static inline bool fw_writes_is_enabled(struct kvm_vcpu *vcpu)
 {
 	return (vcpu_get_perf_capabilities(vcpu) & PERF_CAP_FW_WRITES) != 0;
@@ -456,7 +448,7 @@  static void intel_pmu_enable_fixed_counter_bits(struct kvm_pmu *pmu, u64 bits)
 		pmu->fixed_ctr_ctrl_rsvd &= ~intel_fixed_bits_by_idx(i, bits);
 }
 
-static void intel_pmu_refresh(struct kvm_vcpu *vcpu)
+static void __intel_pmu_refresh(struct kvm_vcpu *vcpu)
 {
 	struct kvm_pmu *pmu = vcpu_to_pmu(vcpu);
 	struct lbr_desc *lbr_desc = vcpu_to_lbr_desc(vcpu);
@@ -564,6 +556,14 @@  static void intel_pmu_refresh(struct kvm_vcpu *vcpu)
 	}
 }
 
+static void intel_pmu_refresh(struct kvm_vcpu *vcpu)
+{
+	__intel_pmu_refresh(vcpu);
+
+	exec_controls_changebit(to_vmx(vcpu), CPU_BASED_RDPMC_EXITING,
+				!kvm_rdpmc_in_guest(vcpu));
+}
+
 static void intel_pmu_init(struct kvm_vcpu *vcpu)
 {
 	int i;