KVM: x86: Adjust counter sample period after a wrmsr

The sample_period of a counter tracks when that counter will
overflow and set global status/trigger a PMI. However this currently
only gets set when the initial counter is created or when a counter is
resumed; this updates the sample period after a wrmsr so running
counters will accurately reflect their new value.

Signed-off-by: Eric Hankland <ehankland@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c
index bcc6a73d6628781809f781abfc0b372450af7106..d1f8ca57d354fb6025e9f675b382b7ca9b6f8992 100644 (file)
--- a/arch/x86/kvm/pmu.c
+++ b/arch/x86/kvm/pmu.c
@@ -111,7 +111,7 @@ static void pmc_reprogram_counter(struct kvm_pmc *pmc, u32 type,
                .config = config,
        };
 
-       attr.sample_period = (-pmc->counter) & pmc_bitmask(pmc);
+       attr.sample_period = get_sample_period(pmc, pmc->counter);
 
        if (in_tx)
                attr.config |= HSW_IN_TX;
@@ -158,7 +158,7 @@ static bool pmc_resume_counter(struct kvm_pmc *pmc)
 
        /* recalibrate sample period and check if it's accepted by perf core */
        if (perf_event_period(pmc->perf_event,
-                       (-pmc->counter) & pmc_bitmask(pmc)))
+                             get_sample_period(pmc, pmc->counter)))
                return false;
 
        /* reuse perf_event to serve as pmc_reprogram_counter() does*/

diff --git a/arch/x86/kvm/pmu.h b/arch/x86/kvm/pmu.h
index 13332984b6d5913389086cf37654daf62dd2702f..d7da2b9e0755e4be9dc7f944cdd1120c0006c732 100644 (file)
--- a/arch/x86/kvm/pmu.h
+++ b/arch/x86/kvm/pmu.h
@@ -129,6 +129,15 @@ static inline struct kvm_pmc *get_fixed_pmc(struct kvm_pmu *pmu, u32 msr)
        return NULL;
 }
 
+static inline u64 get_sample_period(struct kvm_pmc *pmc, u64 counter_value)
+{
+       u64 sample_period = (-counter_value) & pmc_bitmask(pmc);
+
+       if (!sample_period)
+               sample_period = pmc_bitmask(pmc) + 1;
+       return sample_period;
+}
+
 void reprogram_gp_counter(struct kvm_pmc *pmc, u64 eventsel);
 void reprogram_fixed_counter(struct kvm_pmc *pmc, u8 ctrl, int fixed_idx);
 void reprogram_counter(struct kvm_pmu *pmu, int pmc_idx);

diff --git a/arch/x86/kvm/vmx/pmu_intel.c b/arch/x86/kvm/vmx/pmu_intel.c
index fd21cdb10b794407328f66a711a62107ac055053..e933541751fb0fc8366b9bfb36ab7f786189ae69 100644 (file)
--- a/arch/x86/kvm/vmx/pmu_intel.c
+++ b/arch/x86/kvm/vmx/pmu_intel.c
@@ -263,9 +263,15 @@ static int intel_pmu_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
                        if (!msr_info->host_initiated)
                                data = (s64)(s32)data;
                        pmc->counter += data - pmc_read_counter(pmc);
+                       if (pmc->perf_event)
+                               perf_event_period(pmc->perf_event,
+                                                 get_sample_period(pmc, data));
                        return 0;
                } else if ((pmc = get_fixed_pmc(pmu, msr))) {
                        pmc->counter += data - pmc_read_counter(pmc);
+                       if (pmc->perf_event)
+                               perf_event_period(pmc->perf_event,
+                                                 get_sample_period(pmc, data));
                        return 0;
                } else if ((pmc = get_gp_pmc(pmu, msr, MSR_P6_EVNTSEL0))) {
                        if (data == pmc->eventsel)