diff mbox series

[RFC,v3,22/58] KVM: x86/pmu: Add host_perf_cap and initialize it in kvm_x86_vendor_init()

Message ID 20240801045907.4010984-23-mizhang@google.com (mailing list archive)
State New, archived
Headers show
Series Mediated Passthrough vPMU 3.0 for x86 | expand

Commit Message

Mingwei Zhang Aug. 1, 2024, 4:58 a.m. UTC 
Initialize host_perf_cap early in kvm_x86_vendor_init(). This helps KVM
recognize the HW PMU capability against its guest VMs.  This awareness
directly decides the feasibility of passing through RDPMC and indirectly
affects the performance in PMU context switch. Having the host PMU feature
set cached in host_perf_cap saves a rdmsrl() to IA32_PERF_CAPABILITY MSR on
each PMU context switch.

In addition, just opportunistically remove the host_perf_cap initialization
in vmx_get_perf_capabilities() so the value is not dependent on module
parameter "enable_pmu".

Signed-off-by: Mingwei Zhang <mizhang@google.com>
Tested-by: Yongwei Ma <yongwei.ma@intel.com>
---
 arch/x86/kvm/pmu.h     | 1 +
 arch/x86/kvm/vmx/vmx.c | 4 ----
 arch/x86/kvm/x86.c     | 6 ++++++
 3 files changed, 7 insertions(+), 4 deletions(-)
diff mbox series

Patch

diff --git a/arch/x86/kvm/pmu.h b/arch/x86/kvm/pmu.h
index 56ba0772568c..e041c8a23e2f 100644
--- a/arch/x86/kvm/pmu.h
+++ b/arch/x86/kvm/pmu.h
@@ -295,4 +295,5 @@  bool is_vmware_backdoor_pmc(u32 pmc_idx);
 
 extern struct kvm_pmu_ops intel_pmu_ops;
 extern struct kvm_pmu_ops amd_pmu_ops;
+extern u64 __read_mostly host_perf_cap;
 #endif /* __KVM_X86_PMU_H */
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 2ad122995f11..4d60a8cf2dd1 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -7918,14 +7918,10 @@  void vmx_vcpu_after_set_cpuid(struct kvm_vcpu *vcpu)
 static __init u64 vmx_get_perf_capabilities(void)
 {
 	u64 perf_cap = PMU_CAP_FW_WRITES;
-	u64 host_perf_cap = 0;
 
 	if (!enable_pmu)
 		return 0;
 
-	if (boot_cpu_has(X86_FEATURE_PDCM))
-		rdmsrl(MSR_IA32_PERF_CAPABILITIES, host_perf_cap);
-
 	if (!cpu_feature_enabled(X86_FEATURE_ARCH_LBR) &&
 	    !enable_passthrough_pmu) {
 		x86_perf_get_lbr(&vmx_lbr_caps);
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 0c40f551130e..6db4dc496d2b 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -239,6 +239,9 @@  EXPORT_SYMBOL_GPL(host_xss);
 u64 __read_mostly host_arch_capabilities;
 EXPORT_SYMBOL_GPL(host_arch_capabilities);
 
+u64 __read_mostly host_perf_cap;
+EXPORT_SYMBOL_GPL(host_perf_cap);
+
 const struct _kvm_stats_desc kvm_vm_stats_desc[] = {
 	KVM_GENERIC_VM_STATS(),
 	STATS_DESC_COUNTER(VM, mmu_shadow_zapped),
@@ -9793,6 +9796,9 @@  int kvm_x86_vendor_init(struct kvm_x86_init_ops *ops)
 	if (boot_cpu_has(X86_FEATURE_ARCH_CAPABILITIES))
 		rdmsrl(MSR_IA32_ARCH_CAPABILITIES, host_arch_capabilities);
 
+	if (boot_cpu_has(X86_FEATURE_PDCM))
+		rdmsrl(MSR_IA32_PERF_CAPABILITIES, host_perf_cap);
+
 	r = ops->hardware_setup();
 	if (r != 0)
 		goto out_mmu_exit;