[PATCH 4/7] Revert "KVM: x86: always allow host-initiated writes to PMU MSRs"

Sean Christopherson
2022-06-11T00:59:24Z

Revert the hack to allow host-initiated accesses to all "PMU" MSRs,
as intel_is_valid_msr() returns true for _all_ MSRs, regardless of whether
or not it has a snowball's chance in hell of actually being a PMU MSR.

That mostly gets papered over by the actual get/set helpers only handling
MSRs that they knows about, except there's the minor detail that
kvm_pmu_{g,s}et_msr() eat reads and writes when the PMU is disabled.
I.e. KVM will happy allow reads and writes to _any_ MSR if the PMU is
disabled, either via module param or capability.

This reverts commit d1c88a4020567ba4da52f778bcd9619d87e4ea75.

Fixes: d1c88a402056 ("KVM: x86: always allow host-initiated writes to PMU MSRs")
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
arch/x86/kvm/pmu.c | 4 ++--
arch/x86/kvm/pmu.h | 4 ++--
arch/x86/kvm/svm/pmu.c | 2 +-
arch/x86/kvm/vmx/pmu_intel.c | 27 ++++++++++-----------------
arch/x86/kvm/x86.c | 10 +++++-----
5 files changed, 20 insertions(+), 27 deletions(-)

diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c
index 87483e503c46..02f9e4f245bd 100644
--- a/arch/x86/kvm/pmu.c
+++ b/arch/x86/kvm/pmu.c
@@ -425,10 +425,10 @@ void kvm_pmu_deliver_pmi(struct kvm_vcpu *vcpu)
}
}

-bool kvm_pmu_is_valid_msr(struct kvm_vcpu *vcpu, u32 msr, bool host_initiated)
+bool kvm_pmu_is_valid_msr(struct kvm_vcpu *vcpu, u32 msr)
{
return static_call(kvm_x86_pmu_msr_idx_to_pmc)(vcpu, msr) ||
- static_call(kvm_x86_pmu_is_valid_msr)(vcpu, msr, host_initiated);
+ static_call(kvm_x86_pmu_is_valid_msr)(vcpu, msr);
}

static void kvm_pmu_mark_pmc_in_use(struct kvm_vcpu *vcpu, u32 msr)
diff --git a/arch/x86/kvm/pmu.h b/arch/x86/kvm/pmu.h
index c1b61671ba1e..5cc5721f260b 100644
--- a/arch/x86/kvm/pmu.h
+++ b/arch/x86/kvm/pmu.h
@@ -32,7 +32,7 @@ struct kvm_pmu_ops {
unsigned int idx, u64 *mask);
struct kvm_pmc *(*msr_idx_to_pmc)(struct kvm_vcpu *vcpu, u32 msr);
bool (*is_valid_rdpmc_ecx)(struct kvm_vcpu *vcpu, unsigned int idx);
- bool (*is_valid_msr)(struct kvm_vcpu *vcpu, u32 msr, bool host_initiated);
+ bool (*is_valid_msr)(struct kvm_vcpu *vcpu, u32 msr);
int (*get_msr)(struct kvm_vcpu *vcpu, struct msr_data *msr_info);
int (*set_msr)(struct kvm_vcpu *vcpu, struct msr_data *msr_info);
void (*refresh)(struct kvm_vcpu *vcpu);
@@ -189,7 +189,7 @@ void kvm_pmu_deliver_pmi(struct kvm_vcpu *vcpu);
void kvm_pmu_handle_event(struct kvm_vcpu *vcpu);
int kvm_pmu_rdpmc(struct kvm_vcpu *vcpu, unsigned pmc, u64 *data);
bool kvm_pmu_is_valid_rdpmc_ecx(struct kvm_vcpu *vcpu, unsigned int idx);
-bool kvm_pmu_is_valid_msr(struct kvm_vcpu *vcpu, u32 msr, bool host_initiated);
+bool kvm_pmu_is_valid_msr(struct kvm_vcpu *vcpu, u32 msr);
int kvm_pmu_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info);
int kvm_pmu_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info);
void kvm_pmu_refresh(struct kvm_vcpu *vcpu);
diff --git a/arch/x86/kvm/svm/pmu.c b/arch/x86/kvm/svm/pmu.c
index 256244b8f89c..f24613a108c5 100644
--- a/arch/x86/kvm/svm/pmu.c
+++ b/arch/x86/kvm/svm/pmu.c
@@ -179,7 +179,7 @@ static struct kvm_pmc *amd_rdpmc_ecx_to_pmc(struct kvm_vcpu *vcpu,
return &counters[idx];
}

-static bool amd_is_valid_msr(struct kvm_vcpu *vcpu, u32 msr, bool host_initiated)
+static bool amd_is_valid_msr(struct kvm_vcpu *vcpu, u32 msr)
{
/* All MSRs refer to exactly one PMC, so msr_idx_to_pmc is enough. */
return false;
diff --git a/arch/x86/kvm/vmx/pmu_intel.c b/arch/x86/kvm/vmx/pmu_intel.c
index b62012766226..b1aae60cf061 100644
--- a/arch/x86/kvm/vmx/pmu_intel.c
+++ b/arch/x86/kvm/vmx/pmu_intel.c
@@ -196,45 +196,38 @@ static bool intel_pmu_is_valid_lbr_msr(struct kvm_vcpu *vcpu, u32 index)
return ret;
}

-static bool intel_is_valid_msr(struct kvm_vcpu *vcpu, u32 msr, bool host_initiated)
+static bool intel_is_valid_msr(struct kvm_vcpu *vcpu, u32 msr)
{
struct kvm_pmu *pmu = vcpu_to_pmu(vcpu);
u64 perf_capabilities = vcpu->arch.perf_capabilities;
+ int ret;

switch (msr) {
case MSR_CORE_PERF_FIXED_CTR_CTRL:
case MSR_CORE_PERF_GLOBAL_STATUS:
case MSR_CORE_PERF_GLOBAL_CTRL:
case MSR_CORE_PERF_GLOBAL_OVF_CTRL:
- if (host_initiated)
- return true;
- return pmu->version > 1;
+ ret = pmu->version > 1;
break;
case MSR_IA32_PEBS_ENABLE:
- if (host_initiated)
- return true;
- return perf_capabilities & PERF_CAP_PEBS_FORMAT;
+ ret = perf_capabilities & PERF_CAP_PEBS_FORMAT;
break;
case MSR_IA32_DS_AREA:
- if (host_initiated)
- return true;
- return guest_cpuid_has(vcpu, X86_FEATURE_DS);
+ ret = guest_cpuid_has(vcpu, X86_FEATURE_DS);
break;
case MSR_PEBS_DATA_CFG:
- if (host_initiated)
- return true;
- return (perf_capabilities & PERF_CAP_PEBS_BASELINE) &&
+ ret = (perf_capabilities & PERF_CAP_PEBS_BASELINE) &&
((perf_capabilities & PERF_CAP_PEBS_FORMAT) > 3);
break;
default:
- if (host_initiated)
- return true;
- return get_gp_pmc(pmu, msr, MSR_IA32_PERFCTR0) ||
+ ret = get_gp_pmc(pmu, msr, MSR_IA32_PERFCTR0) ||
get_gp_pmc(pmu, msr, MSR_P6_EVNTSEL0) ||
get_fixed_pmc(pmu, msr) || get_fw_gp_pmc(pmu, msr) ||
intel_pmu_is_valid_lbr_msr(vcpu, msr);
break;
}
+
+ return ret;
}

static struct kvm_pmc *intel_msr_idx_to_pmc(struct kvm_vcpu *vcpu, u32 msr)
@@ -596,7 +589,7 @@ static void intel_pmu_refresh(struct kvm_vcpu *vcpu)
INTEL_PMC_MAX_GENERIC, pmu->nr_arch_fixed_counters);

nested_vmx_pmu_refresh(vcpu,
- intel_is_valid_msr(vcpu, MSR_CORE_PERF_GLOBAL_CTRL, false));
+ intel_is_valid_msr(vcpu, MSR_CORE_PERF_GLOBAL_CTRL));

if (cpuid_model_is_consistent(vcpu))
x86_perf_get_lbr(&lbr_desc->records);
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 5d1beb7d310e..25f471adb8b8 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3704,7 +3704,7 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
fallthrough;
case MSR_K7_EVNTSEL0 ... MSR_K7_EVNTSEL3:
case MSR_P6_EVNTSEL0 ... MSR_P6_EVNTSEL1:
- if (kvm_pmu_is_valid_msr(vcpu, msr, msr_info->host_initiated))
+ if (kvm_pmu_is_valid_msr(vcpu, msr))
return kvm_pmu_set_msr(vcpu, msr_info);

if (pr || data != 0)
@@ -3787,7 +3787,7 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
break;
#endif
default:
- if (kvm_pmu_is_valid_msr(vcpu, msr, msr_info->host_initiated))
+ if (kvm_pmu_is_valid_msr(vcpu, msr))
return kvm_pmu_set_msr(vcpu, msr_info);
return KVM_MSR_RET_INVALID;
}
@@ -3867,7 +3867,7 @@ int kvm_get_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
msr_info->data = 0;
break;
case MSR_F15H_PERF_CTL0 ... MSR_F15H_PERF_CTR5:
- if (kvm_pmu_is_valid_msr(vcpu, msr_info->index, msr_info->host_initiated))
+ if (kvm_pmu_is_valid_msr(vcpu, msr_info->index))
return kvm_pmu_get_msr(vcpu, msr_info);
if (!msr_info->host_initiated)
return 1;
@@ -3877,7 +3877,7 @@ int kvm_get_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
case MSR_K7_PERFCTR0 ... MSR_K7_PERFCTR3:
case MSR_P6_PERFCTR0 ... MSR_P6_PERFCTR1:
case MSR_P6_EVNTSEL0 ... MSR_P6_EVNTSEL1:
- if (kvm_pmu_is_valid_msr(vcpu, msr_info->index, msr_info->host_initiated))
+ if (kvm_pmu_is_valid_msr(vcpu, msr_info->index))
return kvm_pmu_get_msr(vcpu, msr_info);
msr_info->data = 0;
break;
@@ -4123,7 +4123,7 @@ int kvm_get_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
break;
#endif
default:
- if (kvm_pmu_is_valid_msr(vcpu, msr_info->index, msr_info->host_initiated))
+ if (kvm_pmu_is_valid_msr(vcpu, msr_info->index))
return kvm_pmu_get_msr(vcpu, msr_info);
return KVM_MSR_RET_INVALID;
}
--
2.36.1.476.g0c4daa206d-goog