@@ -184,6 +184,10 @@ static int has_triple_fault_event;
static bool has_msr_mcg_ext_ctl;
static int pmu_cap;
+/*
+ * Read from /sys/module/kvm/parameters/enable_pmu.
+ */
+static bool kvm_pmu_disabled;
static struct kvm_cpuid2 *cpuid_cache;
static struct kvm_cpuid2 *hv_cpuid_cache;
@@ -2041,23 +2045,30 @@ int kvm_arch_pre_create_vcpu(CPUState *cpu, Error **errp)
if (first) {
first = false;
- /*
- * Since Linux v5.18, KVM provides a VM-level capability to easily
- * disable PMUs; however, QEMU has been providing PMU property per
- * CPU since v1.6. In order to accommodate both, have to configure
- * the VM-level capability here.
- *
- * KVM_PMU_CAP_DISABLE doesn't change the PMU
- * behavior on Intel platform because current "pmu" property works
- * as expected.
- */
- if ((pmu_cap & KVM_PMU_CAP_DISABLE) && !X86_CPU(cpu)->enable_pmu) {
- ret = kvm_vm_enable_cap(kvm_state, KVM_CAP_PMU_CAPABILITY, 0,
- KVM_PMU_CAP_DISABLE);
- if (ret < 0) {
- error_setg_errno(errp, -ret,
- "Failed to set KVM_PMU_CAP_DISABLE");
- return ret;
+ if (X86_CPU(cpu)->enable_pmu) {
+ if (kvm_pmu_disabled) {
+ warn_report("Failed to enable PMU since "
+ "KVM's enable_pmu parameter is disabled");
+ }
+ } else {
+ /*
+ * Since Linux v5.18, KVM provides a VM-level capability to easily
+ * disable PMUs; however, QEMU has been providing PMU property per
+ * CPU since v1.6. In order to accommodate both, have to configure
+ * the VM-level capability here.
+ *
+ * KVM_PMU_CAP_DISABLE doesn't change the PMU
+ * behavior on Intel platform because current "pmu" property works
+ * as expected.
+ */
+ if (pmu_cap & KVM_PMU_CAP_DISABLE) {
+ ret = kvm_vm_enable_cap(kvm_state, KVM_CAP_PMU_CAPABILITY, 0,
+ KVM_PMU_CAP_DISABLE);
+ if (ret < 0) {
+ error_setg_errno(errp, -ret,
+ "Failed to set KVM_PMU_CAP_DISABLE");
+ return ret;
+ }
}
}
}
@@ -3252,6 +3263,7 @@ int kvm_arch_init(MachineState *ms, KVMState *s)
int ret;
struct utsname utsname;
Error *local_err = NULL;
+ g_autofree char *kvm_enable_pmu;
/*
* Initialize SEV context, if required
@@ -3397,6 +3409,21 @@ int kvm_arch_init(MachineState *ms, KVMState *s)
pmu_cap = kvm_check_extension(s, KVM_CAP_PMU_CAPABILITY);
+ /*
+ * The enable_pmu parameter is introduced since Linux v5.17,
+ * give a chance to provide more information about vPMU
+ * enablement.
+ *
+ * The kvm.enable_pmu's permission is 0444. It does not change
+ * until a reload of the KVM module.
+ */
+ if (g_file_get_contents("/sys/module/kvm/parameters/enable_pmu",
+ &kvm_enable_pmu, NULL, NULL)) {
+ if (*kvm_enable_pmu == 'N') {
+ kvm_pmu_disabled = true;
+ }
+ }
+
return 0;
}
When PMU is enabled in QEMU, there is a chance that PMU virtualization is completely disabled by the KVM module parameter kvm.enable_pmu=N. The kvm.enable_pmu parameter is introduced since Linux v5.17. Its permission is 0444. It does not change until a reload of the KVM module. Read the kvm.enable_pmu value from the module sysfs to give a chance to provide more information about vPMU enablement. Signed-off-by: Dongli Zhang <dongli.zhang@oracle.com> --- Changed since v2: - Rework the code flow following Zhao's suggestion. - Return error when: (*kvm_enable_pmu == 'N' && X86_CPU(cpu)->enable_pmu) Changed since v3: - Re-split the cases into enable_pmu and !enable_pmu, following Zhao's suggestion. - Rework the commit messages. - Bring back global static variable 'kvm_pmu_disabled' from v2. target/i386/kvm/kvm.c | 61 +++++++++++++++++++++++++++++++------------ 1 file changed, 44 insertions(+), 17 deletions(-)