From de0f619564f4713bd548b82d535a954ffa1ee7d8 Mon Sep 17 00:00:00 2001 From: Like Xu Date: Fri, 23 Sep 2022 00:13:55 +0000 Subject: [PATCH] KVM: x86/pmu: Defer counter emulated overflow via pmc->prev_counter Defer reprogramming counters and handling overflow via KVM_REQ_PMU when incrementing counters. KVM skips emulated WRMSR in the VM-Exit fastpath, the fastpath runs with IRQs disabled, skipping instructions can increment and reprogram counters, reprogramming counters can sleep, and sleeping is disallowed while IRQs are disabled. [*] BUG: sleeping function called from invalid context at kernel/locking/mutex.c:580 [*] in_atomic(): 1, irqs_disabled(): 1, non_block: 0, pid: 2981888, name: CPU 15/KVM [*] preempt_count: 1, expected: 0 [*] RCU nest depth: 0, expected: 0 [*] INFO: lockdep is turned off. [*] irq event stamp: 0 [*] hardirqs last enabled at (0): [<0000000000000000>] 0x0 [*] hardirqs last disabled at (0): [] copy_process+0x146a/0x62d0 [*] softirqs last enabled at (0): [] copy_process+0x14a9/0x62d0 [*] softirqs last disabled at (0): [<0000000000000000>] 0x0 [*] Preemption disabled at: [*] [] vcpu_enter_guest+0x1001/0x3dc0 [kvm] [*] CPU: 17 PID: 2981888 Comm: CPU 15/KVM Kdump: 5.19.0-rc1-g239111db364c-dirty #2 [*] Call Trace: [*] [*] dump_stack_lvl+0x6c/0x9b [*] __might_resched.cold+0x22e/0x297 [*] __mutex_lock+0xc0/0x23b0 [*] perf_event_ctx_lock_nested+0x18f/0x340 [*] perf_event_pause+0x1a/0x110 [*] reprogram_counter+0x2af/0x1490 [kvm] [*] kvm_pmu_trigger_event+0x429/0x950 [kvm] [*] kvm_skip_emulated_instruction+0x48/0x90 [kvm] [*] handle_fastpath_set_msr_irqoff+0x349/0x3b0 [kvm] [*] vmx_vcpu_run+0x268e/0x3b80 [kvm_intel] [*] vcpu_enter_guest+0x1d22/0x3dc0 [kvm] Add a field to kvm_pmc to track the previous counter value in order to defer overflow detection to kvm_pmu_handle_event() (the counter must be paused before handling overflow, and that may increment the counter). Opportunistically shrink sizeof(struct kvm_pmc) a bit. Suggested-by: Wanpeng Li Fixes: 9cd803d496e7 ("KVM: x86: Update vPMCs when retiring instructions") Signed-off-by: Like Xu Link: https://lore.kernel.org/r/20220831085328.45489-6-likexu@tencent.com [sean: avoid re-triggering KVM_REQ_PMU on overflow, tweak changelog] Signed-off-by: Sean Christopherson Message-Id: <20220923001355.3741194-5-seanjc@google.com> Signed-off-by: Paolo Bonzini --- arch/x86/include/asm/kvm_host.h | 5 +++-- arch/x86/kvm/pmu.c | 32 ++++++++++++++++---------------- arch/x86/kvm/svm/pmu.c | 2 +- arch/x86/kvm/vmx/pmu_intel.c | 4 ++-- 4 files changed, 22 insertions(+), 21 deletions(-) diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index afadbc4b72c4..81114a376c4e 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -491,7 +491,10 @@ enum pmc_type { struct kvm_pmc { enum pmc_type type; u8 idx; + bool is_paused; + bool intr; u64 counter; + u64 prev_counter; u64 eventsel; struct perf_event *perf_event; struct kvm_vcpu *vcpu; @@ -501,8 +504,6 @@ struct kvm_pmc { * ctrl value for fixed counters. */ u64 current_config; - bool is_paused; - bool intr; }; /* More counters may conflict with other existing Architectural MSRs */ diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c index 3054b35b4143..684393c22105 100644 --- a/arch/x86/kvm/pmu.c +++ b/arch/x86/kvm/pmu.c @@ -101,14 +101,6 @@ static inline void __kvm_perf_overflow(struct kvm_pmc *pmc, bool in_pmi) struct kvm_pmu *pmu = pmc_to_pmu(pmc); bool skip_pmi = false; - /* - * Ignore overflow events for counters that are scheduled to be - * reprogrammed, e.g. if a PMI for the previous event races with KVM's - * handling of a related guest WRMSR. - */ - if (test_and_set_bit(pmc->idx, pmu->reprogram_pmi)) - return; - if (pmc->perf_event && pmc->perf_event->attr.precise_ip) { if (!in_pmi) { /* @@ -126,7 +118,6 @@ static inline void __kvm_perf_overflow(struct kvm_pmc *pmc, bool in_pmi) } else { __set_bit(pmc->idx, (unsigned long *)&pmu->global_status); } - kvm_make_request(KVM_REQ_PMU, pmc->vcpu); if (!pmc->intr || skip_pmi) return; @@ -151,7 +142,17 @@ static void kvm_perf_overflow(struct perf_event *perf_event, { struct kvm_pmc *pmc = perf_event->overflow_handler_context; + /* + * Ignore overflow events for counters that are scheduled to be + * reprogrammed, e.g. if a PMI for the previous event races with KVM's + * handling of a related guest WRMSR. + */ + if (test_and_set_bit(pmc->idx, pmc_to_pmu(pmc)->reprogram_pmi)) + return; + __kvm_perf_overflow(pmc, true); + + kvm_make_request(KVM_REQ_PMU, pmc->vcpu); } static int pmc_reprogram_counter(struct kvm_pmc *pmc, u32 type, u64 config, @@ -311,6 +312,9 @@ static void reprogram_counter(struct kvm_pmc *pmc) if (!check_pmu_event_filter(pmc)) goto reprogram_complete; + if (pmc->counter < pmc->prev_counter) + __kvm_perf_overflow(pmc, false); + if (eventsel & ARCH_PERFMON_EVENTSEL_PIN_CONTROL) printk_once("kvm pmu: pin control bit is ignored\n"); @@ -348,6 +352,7 @@ static void reprogram_counter(struct kvm_pmc *pmc) reprogram_complete: clear_bit(pmc->idx, (unsigned long *)&pmc_to_pmu(pmc)->reprogram_pmi); + pmc->prev_counter = 0; } void kvm_pmu_handle_event(struct kvm_vcpu *vcpu) @@ -536,14 +541,9 @@ void kvm_pmu_destroy(struct kvm_vcpu *vcpu) static void kvm_pmu_incr_counter(struct kvm_pmc *pmc) { - u64 prev_count; - - prev_count = pmc->counter; + pmc->prev_counter = pmc->counter; pmc->counter = (pmc->counter + 1) & pmc_bitmask(pmc); - - reprogram_counter(pmc); - if (pmc->counter < prev_count) - __kvm_perf_overflow(pmc, false); + kvm_pmu_request_counter_reprogam(pmc); } static inline bool eventsel_match_perf_hw_id(struct kvm_pmc *pmc, diff --git a/arch/x86/kvm/svm/pmu.c b/arch/x86/kvm/svm/pmu.c index c4b322ffdac4..0e313fbae055 100644 --- a/arch/x86/kvm/svm/pmu.c +++ b/arch/x86/kvm/svm/pmu.c @@ -212,7 +212,7 @@ static void amd_pmu_reset(struct kvm_vcpu *vcpu) struct kvm_pmc *pmc = &pmu->gp_counters[i]; pmc_stop_counter(pmc); - pmc->counter = pmc->eventsel = 0; + pmc->counter = pmc->prev_counter = pmc->eventsel = 0; } } diff --git a/arch/x86/kvm/vmx/pmu_intel.c b/arch/x86/kvm/vmx/pmu_intel.c index 6c80dff37b77..e5cec07ca8d9 100644 --- a/arch/x86/kvm/vmx/pmu_intel.c +++ b/arch/x86/kvm/vmx/pmu_intel.c @@ -646,14 +646,14 @@ static void intel_pmu_reset(struct kvm_vcpu *vcpu) pmc = &pmu->gp_counters[i]; pmc_stop_counter(pmc); - pmc->counter = pmc->eventsel = 0; + pmc->counter = pmc->prev_counter = pmc->eventsel = 0; } for (i = 0; i < KVM_PMC_MAX_FIXED; i++) { pmc = &pmu->fixed_counters[i]; pmc_stop_counter(pmc); - pmc->counter = 0; + pmc->counter = pmc->prev_counter = 0; } pmu->fixed_ctr_ctrl = pmu->global_ctrl = pmu->global_status = 0; -- 2.11.0