KVM: x86/pmu: Handle emulated instruction for mediated vPMU

Mediated vPMU needs to accumulate the emulated instructions into counter
and load the counter into HW at vm-entry.

Moreover, if the accumulation leads to counter overflow, KVM needs to
update GLOBAL_STATUS and inject PMI into guest as well.

Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Dapeng Mi <dapeng1.mi@linux.intel.com>
Signed-off-by: Mingwei Zhang <mizhang@google.com>
Tested-by: Xudong Hao <xudong.hao@intel.com>
Tested-by: Manali Shukla <manali.shukla@amd.com>
Link: https://patch.msgid.link/20251206001720.468579-30-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c
index f6387c67b25c4a165185e00127f5540aa3747be2..b78ad897886dddb203dc1203804d1ef608c91787 100644 (file)
--- a/arch/x86/kvm/pmu.c
+++ b/arch/x86/kvm/pmu.c
@@ -1031,10 +1031,45 @@ void kvm_pmu_destroy(struct kvm_vcpu *vcpu)
        kvm_pmu_reset(vcpu);
 }
 
+static bool pmc_is_pmi_enabled(struct kvm_pmc *pmc)
+{
+       u8 fixed_ctr_ctrl;
+
+       if (pmc_is_gp(pmc))
+               return pmc->eventsel & ARCH_PERFMON_EVENTSEL_INT;
+
+       fixed_ctr_ctrl = fixed_ctrl_field(pmc_to_pmu(pmc)->fixed_ctr_ctrl,
+                                         pmc->idx - KVM_FIXED_PMC_BASE_IDX);
+       return fixed_ctr_ctrl & INTEL_FIXED_0_ENABLE_PMI;
+}
+
 static void kvm_pmu_incr_counter(struct kvm_pmc *pmc)
 {
-       pmc->emulated_counter++;
-       kvm_pmu_request_counter_reprogram(pmc);
+       struct kvm_vcpu *vcpu = pmc->vcpu;
+
+       /*
+        * For perf-based PMUs, accumulate software-emulated events separately
+        * from pmc->counter, as pmc->counter is offset by the count of the
+        * associated perf event. Request reprogramming, which will consult
+        * both emulated and hardware-generated events to detect overflow.
+        */
+       if (!kvm_vcpu_has_mediated_pmu(vcpu)) {
+               pmc->emulated_counter++;
+               kvm_pmu_request_counter_reprogram(pmc);
+               return;
+       }
+
+       /*
+        * For mediated PMUs, pmc->counter is updated when the vCPU's PMU is
+        * put, and will be loaded into hardware when the PMU is loaded. Simply
+        * increment the counter and signal overflow if it wraps to zero.
+        */
+       pmc->counter = (pmc->counter + 1) & pmc_bitmask(pmc);
+       if (!pmc->counter) {
+               pmc_to_pmu(pmc)->global_status |= BIT_ULL(pmc->idx);
+               if (pmc_is_pmi_enabled(pmc))
+                       kvm_make_request(KVM_REQ_PMI, vcpu);
+       }
 }
 
 static inline bool cpl_is_matched(struct kvm_pmc *pmc)