[PATCH 4/4] KVM: x86/pmu: Defer counter emulated overflow via pmc->prev_counter
From: Sean Christopherson
Date: Thu Sep 22 2022 - 20:14:32 EST
From: Like Xu <likexu@xxxxxxxxxxx>
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): [<ffffffff8121222a>] copy_process+0x146a/0x62d0
[*] softirqs last enabled at (0): [<ffffffff81212269>] copy_process+0x14a9/0x62d0
[*] softirqs last disabled at (0): [<0000000000000000>] 0x0
[*] Preemption disabled at:
[*] [<ffffffffc2063fc1>] vcpu_enter_guest+0x1001/0x3dc0 [kvm]
[*] CPU: 17 PID: 2981888 Comm: CPU 15/KVM Kdump: 5.19.0-rc1-g239111db364c-dirty #2
[*] Call Trace:
[*] <TASK>
[*] 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 <wanpengli@xxxxxxxxxxx>
Fixes: 9cd803d496e7 ("KVM: x86: Update vPMCs when retiring instructions")
Signed-off-by: Like Xu <likexu@xxxxxxxxxxx>
Link: https://lore.kernel.org/r/20220831085328.45489-6-likexu@xxxxxxxxxxx
[sean: avoid re-triggering KVM_REQ_PMU on overflow, tweak changelog]
Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
---
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 12dcfc9330e7..9639404f2856 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -488,7 +488,10 @@ 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;
@@ -498,8 +501,6 @@ struct kvm_pmc {
* ctrl value for fixed counters.
*/
u64 current_config;
- bool is_paused;
- bool intr;
};
#define KVM_PMC_MAX_FIXED 3
diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c
index d8330e6064ab..935c9d80ab50 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 041aa898e1bc..2ec420b85d6a 100644
--- a/arch/x86/kvm/svm/pmu.c
+++ b/arch/x86/kvm/svm/pmu.c
@@ -211,7 +211,7 @@ 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 e38518afc265..1bf5d4b00296 100644
--- a/arch/x86/kvm/vmx/pmu_intel.c
+++ b/arch/x86/kvm/vmx/pmu_intel.c
@@ -647,14 +647,14 @@ 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;
--
2.37.3.998.g577e59143f-goog