[v4,26/38] KVM: x86/pmu: Introduce eventsel_hw to prepare for pmu event filtering

Commit Message

Mingwei Zhang March 24, 2025, 5:31 p.m. UTC

Introduce eventsel_hw and fixed_ctr_ctrl_hw to store the actual HW value in
PMU event selector MSRs. In mediated PMU checks events before allowing the
event values written to the PMU MSRs. However, to match the HW behavior,
when PMU event checks fails, KVM should allow guest to read the value back.

This essentially requires an extra variable to separate the guest requested
value from actual PMU MSR value. Note this only applies to event selectors.

Signed-off-by: Mingwei Zhang <[e-mail]>
Co-developed-by: Dapeng Mi <[e-mail]>
Signed-off-by: Dapeng Mi <[e-mail]>
---
 arch/x86/include/asm/kvm_host.h | 2 ++
 arch/x86/kvm/pmu.c              | 7 +++++--
 arch/x86/kvm/svm/pmu.c          | 1 +
 arch/x86/kvm/vmx/pmu_intel.c    | 2 ++
 4 files changed, 10 insertions(+), 2 deletions(-)

Patch

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 4b3bfefc2d05..7ee74bbbb0aa 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -524,6 +524,7 @@  struct kvm_pmc {
 	 */
 	u64 emulated_counter;
 	u64 eventsel;
+	u64 eventsel_hw;
 	struct perf_event *perf_event;
 	struct kvm_vcpu *vcpu;
 	/*
@@ -552,6 +553,7 @@  struct kvm_pmu {
 	unsigned nr_arch_fixed_counters;
 	unsigned available_event_types;
 	u64 fixed_ctr_ctrl;
+	u64 fixed_ctr_ctrl_hw;
 	u64 fixed_ctr_ctrl_rsvd;
 	/*
 	 * kvm_pmu_sync_global_ctrl_from_vmcs() must be called to update
diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c
index 2ac4c039de8b..63143eeb5c44 100644
--- a/arch/x86/kvm/pmu.c
+++ b/arch/x86/kvm/pmu.c
@@ -794,11 +794,14 @@  static void kvm_pmu_reset(struct kvm_vcpu *vcpu)
 		pmc->counter = 0;
 		pmc->emulated_counter = 0;
 
-		if (pmc_is_gp(pmc))
+		if (pmc_is_gp(pmc)) {
 			pmc->eventsel = 0;
+			pmc->eventsel_hw = 0;
+		}
 	}
 
-	pmu->fixed_ctr_ctrl = pmu->global_ctrl = pmu->global_status = 0;
+	pmu->fixed_ctr_ctrl = pmu->fixed_ctr_ctrl_hw = 0;
+	pmu->global_ctrl = pmu->global_status = 0;
 
 	kvm_pmu_call(reset)(vcpu);
 }
diff --git a/arch/x86/kvm/svm/pmu.c b/arch/x86/kvm/svm/pmu.c
index 4fc809c74ba8..9feaca739b96 100644
--- a/arch/x86/kvm/svm/pmu.c
+++ b/arch/x86/kvm/svm/pmu.c
@@ -165,6 +165,7 @@  static int amd_pmu_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 		data &= ~pmu->reserved_bits;
 		if (data != pmc->eventsel) {
 			pmc->eventsel = data;
+			pmc->eventsel_hw = data;
 			kvm_pmu_request_counter_reprogram(pmc);
 		}
 		return 0;
diff --git a/arch/x86/kvm/vmx/pmu_intel.c b/arch/x86/kvm/vmx/pmu_intel.c
index 450f9e5b9e40..796b7bc4affe 100644
--- a/arch/x86/kvm/vmx/pmu_intel.c
+++ b/arch/x86/kvm/vmx/pmu_intel.c
@@ -41,6 +41,7 @@  static void reprogram_fixed_counters(struct kvm_pmu *pmu, u64 data)
 	int i;
 
 	pmu->fixed_ctr_ctrl = data;
+	pmu->fixed_ctr_ctrl_hw = data;
 	for (i = 0; i < pmu->nr_arch_fixed_counters; i++) {
 		u8 new_ctrl = fixed_ctrl_field(data, i);
 		u8 old_ctrl = fixed_ctrl_field(old_fixed_ctr_ctrl, i);
@@ -403,6 +404,7 @@  static int intel_pmu_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 
 			if (data != pmc->eventsel) {
 				pmc->eventsel = data;
+				pmc->eventsel_hw = data;
 				kvm_pmu_request_counter_reprogram(pmc);
 			}
 			break;