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

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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: David Dunn <daviddunn@google.com>
Message-Id: <20220223225743.2703915-2-daviddunn@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
David Dunn 2022-02-23 22:57:41 +00:00 committed by Paolo Bonzini
parent 925088781e
commit ba7bb663f5
7 changed files with 50 additions and 2 deletions
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22
Documentation/virt/kvm/api.rst
View File

@ -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.

1
arch/x86/include/asm/kvm_host.h
View File

@ -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

2
arch/x86/kvm/svm/pmu.c
View File

@ -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) {

2
arch/x86/kvm/vmx/pmu_intel.c
View File

@ -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;

18
arch/x86/kvm/x86.c
View File

@ -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 @@ split_irqchip_unlock:
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);

3
include/uapi/linux/kvm.h
View File

@ -1142,6 +1142,7 @@ struct kvm_ppc_resize_hpt {
#define KVM_CAP_SYS_ATTRIBUTES 209
#define KVM_CAP_PPC_AIL_MODE_3 210
#define KVM_CAP_S390_MEM_OP_EXTENSION 211
#define KVM_CAP_PMU_CAPABILITY 212
#ifdef KVM_CAP_IRQ_ROUTING
@ -1978,6 +1979,8 @@ struct kvm_dirty_gfn {
#define KVM_BUS_LOCK_DETECTION_OFF (1 << 0)
#define KVM_BUS_LOCK_DETECTION_EXIT (1 << 1)
#define KVM_PMU_CAP_DISABLE (1 << 0)
/**
* struct kvm_stats_header - Header of per vm/vcpu binary statistics data.
* @flags: Some extra information for header, always 0 for now.

4
tools/include/uapi/linux/kvm.h
View File

@ -1135,6 +1135,8 @@ struct kvm_ppc_resize_hpt {
#define KVM_CAP_XSAVE2 208
#define KVM_CAP_SYS_ATTRIBUTES 209
#define KVM_CAP_PPC_AIL_MODE_3 210
#define KVM_CAP_S390_MEM_OP_EXTENSION 211
#define KVM_CAP_PMU_CAPABILITY 212
#ifdef KVM_CAP_IRQ_ROUTING
@ -1971,6 +1973,8 @@ struct kvm_dirty_gfn {
#define KVM_BUS_LOCK_DETECTION_OFF (1 << 0)
#define KVM_BUS_LOCK_DETECTION_EXIT (1 << 1)
#define KVM_PMU_CAP_DISABLE (1 << 0)
/**
* struct kvm_stats_header - Header of per vm/vcpu binary statistics data.
* @flags: Some extra information for header, always 0 for now.