Commit ba7bb663 authored by David Dunn's avatar David Dunn Committed by Paolo Bonzini
Browse files

KVM: x86: Provide per VM capability for disabling PMU virtualization 



Add a new capability, KVM_CAP_PMU_CAPABILITY, that takes a bitmask of
settings/features to allow userspace to configure PMU virtualization on
a per-VM basis.  For now, support a single flag, KVM_PMU_CAP_DISABLE,
to allow disabling PMU virtualization for a VM even when KVM is configured
with enable_pmu=true a module level.

To keep KVM simple, disallow changing VM's PMU configuration after vCPUs
have been created.

Signed-off-by: default avatarDavid Dunn <daviddunn@google.com>
Message-Id: <20220223225743.2703915-2-daviddunn@google.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 92508878

Documentation/virt/kvm/api.rst

+22 −0
Original line number Diff line number Diff line
@@ -7643,3 +7643,25 @@ The argument to KVM_ENABLE_CAP is also a bitmask, and must be a subset 
of the result of KVM_CHECK_EXTENSION.  KVM will forward to userspace

the hypercalls whose corresponding bit is in the argument, and return

ENOSYS for the others.



8.35 KVM_CAP_PMU_CAPABILITY

---------------------------



:Capability KVM_CAP_PMU_CAPABILITY

:Architectures: x86

:Type: vm

:Parameters: arg[0] is bitmask of PMU virtualization capabilities.

:Returns 0 on success, -EINVAL when arg[0] contains invalid bits



This capability alters PMU virtualization in KVM.



Calling KVM_CHECK_EXTENSION for this capability returns a bitmask of

PMU virtualization capabilities that can be adjusted on a VM.



The argument to KVM_ENABLE_CAP is also a bitmask and selects specific

PMU virtualization capabilities to be applied to the VM.  This can

only be invoked on a VM prior to the creation of VCPUs.



At this time, KVM_PMU_CAP_DISABLE is the only capability.  Setting

this capability will disable PMU virtualization for that VM.  Usermode

should adjust CPUID leaf 0xA to reflect that the PMU is disabled.

arch/x86/include/asm/kvm_host.h

+1 −0
Original line number Diff line number Diff line
@@ -1147,6 +1147,7 @@ struct kvm_arch { 
	bool exception_payload_enabled;



	bool bus_lock_detection_enabled;

	bool enable_pmu;

	/*

	 * If exit_on_emulation_error is set, and the in-kernel instruction

	 * emulator fails to emulate an instruction, allow userspace

arch/x86/kvm/svm/pmu.c

+1 −1
Original line number Diff line number Diff line
@@ -101,7 +101,7 @@ static inline struct kvm_pmc *get_gp_pmc_amd(struct kvm_pmu *pmu, u32 msr, 
{

	struct kvm_vcpu *vcpu = pmu_to_vcpu(pmu);



	if (!enable_pmu)

	if (!vcpu->kvm->arch.enable_pmu)

		return NULL;



	switch (msr) {

arch/x86/kvm/vmx/pmu_intel.c

+1 −1
Original line number Diff line number Diff line
@@ -487,7 +487,7 @@ static void intel_pmu_refresh(struct kvm_vcpu *vcpu) 
	pmu->reserved_bits = 0xffffffff00200000ull;



	entry = kvm_find_cpuid_entry(vcpu, 0xa, 0);

	if (!entry || !enable_pmu)

	if (!entry || !vcpu->kvm->arch.enable_pmu)

		return;

	eax.full = entry->eax;

	edx.full = entry->edx;

arch/x86/kvm/x86.c

+18 −0
Original line number Diff line number Diff line
@@ -110,6 +110,8 @@ static u64 __read_mostly cr4_reserved_bits = CR4_RESERVED_BITS; 


#define KVM_EXIT_HYPERCALL_VALID_MASK (1 << KVM_HC_MAP_GPA_RANGE)



#define KVM_CAP_PMU_VALID_MASK KVM_PMU_CAP_DISABLE



#define KVM_X2APIC_API_VALID_FLAGS (KVM_X2APIC_API_USE_32BIT_IDS | \

                                    KVM_X2APIC_API_DISABLE_BROADCAST_QUIRK)
@@ -4330,6 +4332,9 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext) 
		if (r < sizeof(struct kvm_xsave))

			r = sizeof(struct kvm_xsave);

		break;

	case KVM_CAP_PMU_CAPABILITY:

		r = enable_pmu ? KVM_CAP_PMU_VALID_MASK : 0;

		break;

	}

	default:

		break;
@@ -6004,6 +6009,18 @@ int kvm_vm_ioctl_enable_cap(struct kvm *kvm, 
		kvm->arch.exit_on_emulation_error = cap->args[0];

		r = 0;

		break;

	case KVM_CAP_PMU_CAPABILITY:

		r = -EINVAL;

		if (!enable_pmu || (cap->args[0] & ~KVM_CAP_PMU_VALID_MASK))

			break;



		mutex_lock(&kvm->lock);

		if (!kvm->created_vcpus) {

			kvm->arch.enable_pmu = !(cap->args[0] & KVM_PMU_CAP_DISABLE);

			r = 0;

		}

		mutex_unlock(&kvm->lock);

		break;

	default:

		r = -EINVAL;

		break;
@@ -11586,6 +11603,7 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type) 
	raw_spin_unlock_irqrestore(&kvm->arch.tsc_write_lock, flags);



	kvm->arch.guest_can_read_msr_platform_info = true;

	kvm->arch.enable_pmu = enable_pmu;



#if IS_ENABLED(CONFIG_HYPERV)

	spin_lock_init(&kvm->arch.hv_root_tdp_lock);