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linux/arch/x86/kvm/pmu.h
Roman Kagan b29a2acd36 KVM: x86/pmu: Truncate counter value to allowed width on write 
Performance counters are defined to have width less than 64 bits.  The
vPMU code maintains the counters in u64 variables but assumes the value
to fit within the defined width.  However, for Intel non-full-width
counters (MSR_IA32_PERFCTRx) the value receieved from the guest is
truncated to 32 bits and then sign-extended to full 64 bits.  If a
negative value is set, it's sign-extended to 64 bits, but then in
kvm_pmu_incr_counter() it's incremented, truncated, and compared to the
previous value for overflow detection.

That previous value is not truncated, so it always evaluates bigger than
the truncated new one, and a PMI is injected.  If the PMI handler writes
a negative counter value itself, the vCPU never quits the PMI loop.

Turns out that Linux PMI handler actually does write the counter with
the value just read with RDPMC, so when no full-width support is exposed
via MSR_IA32_PERF_CAPABILITIES, and the guest initializes the counter to
a negative value, it locks up.

This has been observed in the field, for example, when the guest configures
atop to use perfevents and runs two instances of it simultaneously.

To address the problem, maintain the invariant that the counter value
always fits in the defined bit width, by truncating the received value
in the respective set_msr methods.  For better readability, factor the
out into a helper function, pmc_write_counter(), shared by vmx and svm
parts.

Fixes: 9cd803d496 ("KVM: x86: Update vPMCs when retiring instructions")
Cc: stable@vger.kernel.org
Signed-off-by: Roman Kagan <rkagan@amazon.de>
Link: https://lore.kernel.org/all/20230504120042.785651-1-rkagan@amazon.de
Tested-by: Like Xu <likexu@tencent.com>
[sean: tweak changelog, s/set/write in the helper]
Signed-off-by: Sean Christopherson <seanjc@google.com>
2023-09-25 14:30:44 -07:00

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/* SPDX-License-Identifier: GPL-2.0 */
#ifndef __KVM_X86_PMU_H
#define __KVM_X86_PMU_H
#include <linux/nospec.h>
#define vcpu_to_pmu(vcpu) (&(vcpu)->arch.pmu)
#define pmu_to_vcpu(pmu) (container_of((pmu), struct kvm_vcpu, arch.pmu))
#define pmc_to_pmu(pmc) (&(pmc)->vcpu->arch.pmu)
#define MSR_IA32_MISC_ENABLE_PMU_RO_MASK (MSR_IA32_MISC_ENABLE_PEBS_UNAVAIL | \
MSR_IA32_MISC_ENABLE_BTS_UNAVAIL)
/* retrieve the 4 bits for EN and PMI out of IA32_FIXED_CTR_CTRL */
#define fixed_ctrl_field(ctrl_reg, idx) (((ctrl_reg) >> ((idx)*4)) & 0xf)
#define VMWARE_BACKDOOR_PMC_HOST_TSC 0x10000
#define VMWARE_BACKDOOR_PMC_REAL_TIME 0x10001
#define VMWARE_BACKDOOR_PMC_APPARENT_TIME 0x10002
struct kvm_pmu_ops {
bool (*hw_event_available)(struct kvm_pmc *pmc);
struct kvm_pmc *(*pmc_idx_to_pmc)(struct kvm_pmu *pmu, int pmc_idx);
struct kvm_pmc *(*rdpmc_ecx_to_pmc)(struct kvm_vcpu *vcpu,
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);
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);
void (*init)(struct kvm_vcpu *vcpu);
void (*reset)(struct kvm_vcpu *vcpu);
void (*deliver_pmi)(struct kvm_vcpu *vcpu);
void (*cleanup)(struct kvm_vcpu *vcpu);
const u64 EVENTSEL_EVENT;
const int MAX_NR_GP_COUNTERS;
const int MIN_NR_GP_COUNTERS;
};
void kvm_pmu_ops_update(const struct kvm_pmu_ops *pmu_ops);
static inline bool kvm_pmu_has_perf_global_ctrl(struct kvm_pmu *pmu)
{
/*
* Architecturally, Intel's SDM states that IA32_PERF_GLOBAL_CTRL is
* supported if "CPUID.0AH: EAX[7:0] > 0", i.e. if the PMU version is
* greater than zero. However, KVM only exposes and emulates the MSR
* to/for the guest if the guest PMU supports at least "Architectural
* Performance Monitoring Version 2".
*
* AMD's version of PERF_GLOBAL_CTRL conveniently shows up with v2.
*/
return pmu->version > 1;
}
static inline u64 pmc_bitmask(struct kvm_pmc *pmc)
{
struct kvm_pmu *pmu = pmc_to_pmu(pmc);
return pmu->counter_bitmask[pmc->type];
}
static inline u64 pmc_read_counter(struct kvm_pmc *pmc)
{
u64 counter, enabled, running;
counter = pmc->counter;
if (pmc->perf_event && !pmc->is_paused)
counter += perf_event_read_value(pmc->perf_event,
&enabled, &running);
/* FIXME: Scaling needed? */
return counter & pmc_bitmask(pmc);
}
static inline void pmc_write_counter(struct kvm_pmc *pmc, u64 val)
{
pmc->counter += val - pmc_read_counter(pmc);
pmc->counter &= pmc_bitmask(pmc);
}
static inline void pmc_release_perf_event(struct kvm_pmc *pmc)
{
if (pmc->perf_event) {
perf_event_release_kernel(pmc->perf_event);
pmc->perf_event = NULL;
pmc->current_config = 0;
pmc_to_pmu(pmc)->event_count--;
}
}
static inline void pmc_stop_counter(struct kvm_pmc *pmc)
{
if (pmc->perf_event) {
pmc->counter = pmc_read_counter(pmc);
pmc_release_perf_event(pmc);
}
}
static inline bool pmc_is_gp(struct kvm_pmc *pmc)
{
return pmc->type == KVM_PMC_GP;
}
static inline bool pmc_is_fixed(struct kvm_pmc *pmc)
{
return pmc->type == KVM_PMC_FIXED;
}
static inline bool kvm_valid_perf_global_ctrl(struct kvm_pmu *pmu,
u64 data)
{
return !(pmu->global_ctrl_mask & data);
}
/* returns general purpose PMC with the specified MSR. Note that it can be
* used for both PERFCTRn and EVNTSELn; that is why it accepts base as a
* parameter to tell them apart.
*/
static inline struct kvm_pmc *get_gp_pmc(struct kvm_pmu *pmu, u32 msr,
u32 base)
{
if (msr >= base && msr < base + pmu->nr_arch_gp_counters) {
u32 index = array_index_nospec(msr - base,
pmu->nr_arch_gp_counters);
return &pmu->gp_counters[index];
}
return NULL;
}
/* returns fixed PMC with the specified MSR */
static inline struct kvm_pmc *get_fixed_pmc(struct kvm_pmu *pmu, u32 msr)
{
int base = MSR_CORE_PERF_FIXED_CTR0;
if (msr >= base && msr < base + pmu->nr_arch_fixed_counters) {
u32 index = array_index_nospec(msr - base,
pmu->nr_arch_fixed_counters);
return &pmu->fixed_counters[index];
}
return NULL;
}
static inline u64 get_sample_period(struct kvm_pmc *pmc, u64 counter_value)
{
u64 sample_period = (-counter_value) & pmc_bitmask(pmc);
if (!sample_period)
sample_period = pmc_bitmask(pmc) + 1;
return sample_period;
}
static inline void pmc_update_sample_period(struct kvm_pmc *pmc)
{
if (!pmc->perf_event || pmc->is_paused ||
!is_sampling_event(pmc->perf_event))
return;
perf_event_period(pmc->perf_event,
get_sample_period(pmc, pmc->counter));
}
static inline bool pmc_speculative_in_use(struct kvm_pmc *pmc)
{
struct kvm_pmu *pmu = pmc_to_pmu(pmc);
if (pmc_is_fixed(pmc))
return fixed_ctrl_field(pmu->fixed_ctr_ctrl,
pmc->idx - INTEL_PMC_IDX_FIXED) & 0x3;
return pmc->eventsel & ARCH_PERFMON_EVENTSEL_ENABLE;
}
extern struct x86_pmu_capability kvm_pmu_cap;
static inline void kvm_init_pmu_capability(const struct kvm_pmu_ops *pmu_ops)
{
bool is_intel = boot_cpu_data.x86_vendor == X86_VENDOR_INTEL;
int min_nr_gp_ctrs = pmu_ops->MIN_NR_GP_COUNTERS;
/*
* Hybrid PMUs don't play nice with virtualization without careful
* configuration by userspace, and KVM's APIs for reporting supported
* vPMU features do not account for hybrid PMUs. Disable vPMU support
* for hybrid PMUs until KVM gains a way to let userspace opt-in.
*/
if (cpu_feature_enabled(X86_FEATURE_HYBRID_CPU))
enable_pmu = false;
if (enable_pmu) {
perf_get_x86_pmu_capability(&kvm_pmu_cap);
/*
* WARN if perf did NOT disable hardware PMU if the number of
* architecturally required GP counters aren't present, i.e. if
* there are a non-zero number of counters, but fewer than what
* is architecturally required.
*/
if (!kvm_pmu_cap.num_counters_gp ||
WARN_ON_ONCE(kvm_pmu_cap.num_counters_gp < min_nr_gp_ctrs))
enable_pmu = false;
else if (is_intel && !kvm_pmu_cap.version)
enable_pmu = false;
}
if (!enable_pmu) {
memset(&kvm_pmu_cap, 0, sizeof(kvm_pmu_cap));
return;
}
kvm_pmu_cap.version = min(kvm_pmu_cap.version, 2);
kvm_pmu_cap.num_counters_gp = min(kvm_pmu_cap.num_counters_gp,
pmu_ops->MAX_NR_GP_COUNTERS);
kvm_pmu_cap.num_counters_fixed = min(kvm_pmu_cap.num_counters_fixed,
KVM_PMC_MAX_FIXED);
}
static inline void kvm_pmu_request_counter_reprogram(struct kvm_pmc *pmc)
{
set_bit(pmc->idx, pmc_to_pmu(pmc)->reprogram_pmi);
kvm_make_request(KVM_REQ_PMU, pmc->vcpu);
}
static inline void reprogram_counters(struct kvm_pmu *pmu, u64 diff)
{
int bit;
if (!diff)
return;
for_each_set_bit(bit, (unsigned long *)&diff, X86_PMC_IDX_MAX)
set_bit(bit, pmu->reprogram_pmi);
kvm_make_request(KVM_REQ_PMU, pmu_to_vcpu(pmu));
}
/*
* Check if a PMC is enabled by comparing it against global_ctrl bits.
*
* If the vPMU doesn't have global_ctrl MSR, all vPMCs are enabled.
*/
static inline bool pmc_is_globally_enabled(struct kvm_pmc *pmc)
{
struct kvm_pmu *pmu = pmc_to_pmu(pmc);
if (!kvm_pmu_has_perf_global_ctrl(pmu))
return true;
return test_bit(pmc->idx, (unsigned long *)&pmu->global_ctrl);
}
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);
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);
void kvm_pmu_reset(struct kvm_vcpu *vcpu);
void kvm_pmu_init(struct kvm_vcpu *vcpu);
void kvm_pmu_cleanup(struct kvm_vcpu *vcpu);
void kvm_pmu_destroy(struct kvm_vcpu *vcpu);
int kvm_vm_ioctl_set_pmu_event_filter(struct kvm *kvm, void __user *argp);
void kvm_pmu_trigger_event(struct kvm_vcpu *vcpu, u64 perf_hw_id);
bool is_vmware_backdoor_pmc(u32 pmc_idx);
extern struct kvm_pmu_ops intel_pmu_ops;
extern struct kvm_pmu_ops amd_pmu_ops;
#endif /* __KVM_X86_PMU_H */
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