[PATCH v2 11/16] KVM: x86/pmu: Emulate the GLOBAL_STATUS_SET and GLOBAL_INUSE MSRs
From: Zide Chen
Date: Thu Aug 27 2026 - 18:49:55 EST
Intel PerfMon v4 introduces IA32_PERF_GLOBAL_STATUS_SET (0x391) to
allow software to set individual bits in the global status MSR. Reads
of IA32_PERF_GLOBAL_STATUS_SET always return zero.
IA32_PERF_GLOBAL_INUSE (0x392) is also introduced in v4, to track
which counters and the PMI are currently claimed by other agents,
allowing independent software agents to check counter availability
without a shared scheduler arbitrating between them.
IA32_PERF_GLOBAL_INUSE is an read-only MSR, and any write attempt
results in a #GP.
Neither MSR is part of the VM state, so they don't need to be
advertised to userspace, nor saved and restored during live
migration.
Originally-by: Yang Weijiang <weijiang.yang@xxxxxxxxx>
Signed-off-by: Zide Chen <zide.chen@xxxxxxxxx>
---
v2:
- Change intel_pmu_get_global_inuse() to return u64, to match the
surrounding code style.
- Add the missing vmcs02 updates for these two MSRs.
- Change "> 3" to ">= 4" to make the "v4-gated" more obvious and match
the existing code style.
---
arch/x86/include/asm/msr-index.h | 4 ++++
arch/x86/kvm/pmu.c | 9 ++++++++
arch/x86/kvm/vmx/nested.c | 2 ++
arch/x86/kvm/vmx/pmu_intel.c | 37 ++++++++++++++++++++++++++++++++
arch/x86/kvm/vmx/vmx.c | 4 ++++
5 files changed, 56 insertions(+)
diff --git a/arch/x86/include/asm/msr-index.h b/arch/x86/include/asm/msr-index.h
index 11b99d237e05..0b093cf41edf 100644
--- a/arch/x86/include/asm/msr-index.h
+++ b/arch/x86/include/asm/msr-index.h
@@ -1240,6 +1240,10 @@
#define MSR_CORE_PERF_GLOBAL_CTRL 0x0000038f
#define MSR_CORE_PERF_GLOBAL_OVF_CTRL 0x00000390
#define MSR_CORE_PERF_GLOBAL_STATUS_SET 0x00000391
+#define MSR_CORE_PERF_GLOBAL_INUSE 0x00000392
+
+/* Intel IA32_PERF_GLOBAL_INUSE MSR */
+#define PERF_GLOBAL_INUSE_PMI_INUSE BIT_ULL(63)
#define MSR_PERF_METRICS 0x00000329
diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c
index 437a7bc49bf8..7c05cf5157bf 100644
--- a/arch/x86/kvm/pmu.c
+++ b/arch/x86/kvm/pmu.c
@@ -832,6 +832,8 @@ bool kvm_pmu_is_valid_msr(struct kvm_vcpu *vcpu, u32 msr)
case MSR_CORE_PERF_GLOBAL_CTRL:
case MSR_CORE_PERF_GLOBAL_OVF_CTRL:
return kvm_pmu_has_perf_global_ctrl(vcpu_to_pmu(vcpu));
+ case MSR_CORE_PERF_GLOBAL_STATUS_SET:
+ return vcpu_to_pmu(vcpu)->version >= 4;
default:
break;
}
@@ -865,6 +867,7 @@ int kvm_pmu_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
case MSR_AMD64_PERF_CNTR_GLOBAL_STATUS_CLR:
case MSR_AMD64_PERF_CNTR_GLOBAL_STATUS_SET:
case MSR_CORE_PERF_GLOBAL_OVF_CTRL:
+ case MSR_CORE_PERF_GLOBAL_STATUS_SET:
msr_info->data = 0;
break;
default:
@@ -931,6 +934,12 @@ int kvm_pmu_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
if (!msr_info->host_initiated)
pmu->global_status &= ~data;
break;
+ case MSR_CORE_PERF_GLOBAL_STATUS_SET:
+ if (data & pmu->global_status_rsvd)
+ return 1;
+ if (!msr_info->host_initiated)
+ pmu->global_status |= data;
+ break;
case MSR_AMD64_PERF_CNTR_GLOBAL_STATUS_SET:
if (!msr_info->host_initiated)
pmu->global_status |= data & ~pmu->global_status_rsvd;
diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index 0cff369982ae..ae7dd3636e70 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -719,6 +719,8 @@ static void nested_vmx_merge_pmu_msr_bitmaps(struct kvm_vcpu *vcpu,
nested_vmx_merge_msr_bitmaps_rw(MSR_CORE_PERF_GLOBAL_CTRL);
nested_vmx_merge_msr_bitmaps_read(MSR_CORE_PERF_GLOBAL_STATUS);
nested_vmx_merge_msr_bitmaps_write(MSR_CORE_PERF_GLOBAL_OVF_CTRL);
+ nested_vmx_merge_msr_bitmaps_write(MSR_CORE_PERF_GLOBAL_STATUS_SET);
+ nested_vmx_merge_msr_bitmaps_read(MSR_CORE_PERF_GLOBAL_INUSE);
}
/*
diff --git a/arch/x86/kvm/vmx/pmu_intel.c b/arch/x86/kvm/vmx/pmu_intel.c
index 4df55a3e21da..3070fba2687f 100644
--- a/arch/x86/kvm/vmx/pmu_intel.c
+++ b/arch/x86/kvm/vmx/pmu_intel.c
@@ -194,6 +194,8 @@ static bool intel_is_valid_msr(struct kvm_vcpu *vcpu, u32 msr)
switch (msr) {
case MSR_CORE_PERF_FIXED_CTR_CTRL:
return kvm_pmu_has_perf_global_ctrl(pmu);
+ case MSR_CORE_PERF_GLOBAL_INUSE:
+ return pmu->version >= 4;
case MSR_IA32_PEBS_ENABLE:
ret = vcpu_get_perf_capabilities(vcpu) & PERF_CAP_PEBS_FORMAT;
break;
@@ -341,6 +343,38 @@ static bool intel_pmu_handle_lbr_msrs_access(struct kvm_vcpu *vcpu,
return true;
}
+static u64 intel_pmu_get_global_inuse(struct kvm_vcpu *vcpu)
+{
+ struct kvm_pmu *pmu = vcpu_to_pmu(vcpu);
+ unsigned long fixed_mask = kvm_fixed_pmc_mask(pmu);
+ unsigned long gp_mask = kvm_gp_pmc_mask(pmu);
+ bool pmi_inuse = false;
+ u64 eventsel, data = 0;
+ u32 fixed_ctrl;
+ int i;
+
+ kvm_for_each_gp_counter(i, gp_mask) {
+ eventsel = pmu->gp_counters[i].eventsel;
+
+ if (eventsel & ARCH_PERFMON_EVENTSEL_EVENT)
+ data |= BIT_ULL(i);
+ pmi_inuse |= eventsel & ARCH_PERFMON_EVENTSEL_INT;
+ }
+ kvm_for_each_fixed_counter(i, fixed_mask) {
+ fixed_ctrl = fixed_ctrl_field(pmu->fixed_ctr_ctrl, i);
+
+ if (fixed_ctrl & (INTEL_FIXED_0_KERNEL | INTEL_FIXED_0_USER))
+ data |= BIT_ULL(KVM_FIXED_PMC_BASE_IDX + i);
+ pmi_inuse |= fixed_ctrl & INTEL_FIXED_0_ENABLE_PMI;
+ }
+ pmi_inuse |= pmu->pebs_enable;
+
+ if (pmi_inuse)
+ data |= PERF_GLOBAL_INUSE_PMI_INUSE;
+
+ return data;
+}
+
static int intel_pmu_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
{
struct kvm_pmu *pmu = vcpu_to_pmu(vcpu);
@@ -351,6 +385,9 @@ static int intel_pmu_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
case MSR_CORE_PERF_FIXED_CTR_CTRL:
msr_info->data = pmu->fixed_ctr_ctrl;
break;
+ case MSR_CORE_PERF_GLOBAL_INUSE:
+ msr_info->data = intel_pmu_get_global_inuse(vcpu);
+ break;
case MSR_IA32_PEBS_ENABLE:
msr_info->data = pmu->pebs_enable;
break;
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 56daf5c61082..2dabb7e64956 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -4282,6 +4282,10 @@ static void vmx_recalc_pmu_msr_intercepts(struct kvm_vcpu *vcpu)
MSR_TYPE_RW, intercept);
vmx_set_intercept_for_msr(vcpu, MSR_CORE_PERF_GLOBAL_OVF_CTRL,
MSR_TYPE_RW, intercept);
+ vmx_set_intercept_for_msr(vcpu, MSR_CORE_PERF_GLOBAL_STATUS_SET,
+ MSR_TYPE_RW, intercept || pmu->version < 4);
+ vmx_set_intercept_for_msr(vcpu, MSR_CORE_PERF_GLOBAL_INUSE,
+ MSR_TYPE_RW, intercept || pmu->version < 4);
}
static void vmx_recalc_msr_intercepts(struct kvm_vcpu *vcpu)
--
2.55.0