[PATCH v3 4/4] KVM: x86: Use static calls to reduce kvm_pmu_ops overhead

From: Like Xu
Date: Mon Mar 07 2022 - 07:00:05 EST

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From: Like Xu <likexu@xxxxxxxxxxx>

Use static calls to improve kvm_pmu_ops performance. Introduce the
definitions that will be used by a subsequent patch to actualize the
savings. Add a new kvm-x86-pmu-ops.h header that can be used for the
definition of static calls. This header is also intended to be
used to simplify the defition of amd_pmu_ops and intel_pmu_ops.

Here are the worst fenced_rdtsc() cycles numbers for the kvm_pmu_ops
functions that is most often called (up to 7 digits of calls) when running
a single perf test case in a guest on an ICX 2.70GHz host (mitigations=on):

| legacy | static call
------------------------------------------------------------
.pmc_idx_to_pmc | 1304840 | 994872 (+23%)
.pmc_is_enabled | 978670 | 1011750 (-3%)
.msr_idx_to_pmc | 47828 | 41690 (+12%)
.is_valid_msr | 28786 | 30108 (-4%)

Signed-off-by: Like Xu <likexu@xxxxxxxxxxx>
---
arch/x86/include/asm/kvm-x86-pmu-ops.h | 31 +++++++++++++++++
arch/x86/kvm/pmu.c | 46 ++++++++++++++------------
arch/x86/kvm/pmu.h | 7 +++-
arch/x86/kvm/x86.c | 8 +++++
4 files changed, 70 insertions(+), 22 deletions(-)
create mode 100644 arch/x86/include/asm/kvm-x86-pmu-ops.h

diff --git a/arch/x86/include/asm/kvm-x86-pmu-ops.h b/arch/x86/include/asm/kvm-x86-pmu-ops.h
new file mode 100644
index 000000000000..fdfd8e06fee6
--- /dev/null
+++ b/arch/x86/include/asm/kvm-x86-pmu-ops.h
@@ -0,0 +1,31 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#if !defined(KVM_X86_PMU_OP) || !defined(KVM_X86_PMU_OP_OPTIONAL)
+BUILD_BUG_ON(1)
+#endif
+
+/*
+ * KVM_X86_PMU_OP() and KVM_X86_PMU_OP_OPTIONAL() are used to help generate
+ * both DECLARE/DEFINE_STATIC_CALL() invocations and
+ * "static_call_update()" calls.
+ *
+ * KVM_X86_PMU_OP_OPTIONAL() can be used for those functions that can have
+ * a NULL definition, for example if "static_call_cond()" will be used
+ * at the call sites.
+ */
+KVM_X86_PMU_OP(pmc_perf_hw_id)
+KVM_X86_PMU_OP(pmc_is_enabled)
+KVM_X86_PMU_OP(pmc_idx_to_pmc)
+KVM_X86_PMU_OP(rdpmc_ecx_to_pmc)
+KVM_X86_PMU_OP(msr_idx_to_pmc)
+KVM_X86_PMU_OP(is_valid_rdpmc_ecx)
+KVM_X86_PMU_OP(is_valid_msr)
+KVM_X86_PMU_OP(get_msr)
+KVM_X86_PMU_OP(set_msr)
+KVM_X86_PMU_OP(refresh)
+KVM_X86_PMU_OP(init)
+KVM_X86_PMU_OP(reset)
+KVM_X86_PMU_OP_OPTIONAL(deliver_pmi)
+KVM_X86_PMU_OP_OPTIONAL(cleanup)
+
+#undef KVM_X86_PMU_OP
+#undef KVM_X86_PMU_OP_OPTIONAL
diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c
index 771edc4f4494..4146be236506 100644
--- a/arch/x86/kvm/pmu.c
+++ b/arch/x86/kvm/pmu.c
@@ -51,6 +51,12 @@

struct kvm_pmu_ops kvm_pmu_ops __read_mostly;

+#define KVM_X86_PMU_OP(func) \
+ DEFINE_STATIC_CALL_NULL(kvm_x86_pmu_##func, \
+ *(((struct kvm_pmu_ops *)0)->func));
+#define KVM_X86_PMU_OP_OPTIONAL KVM_X86_PMU_OP
+#include <asm/kvm-x86-pmu-ops.h>
+
static void kvm_pmi_trigger_fn(struct irq_work *irq_work)
{
struct kvm_pmu *pmu = container_of(irq_work, struct kvm_pmu, irq_work);
@@ -217,7 +223,7 @@ void reprogram_gp_counter(struct kvm_pmc *pmc, u64 eventsel)
ARCH_PERFMON_EVENTSEL_CMASK |
HSW_IN_TX |
HSW_IN_TX_CHECKPOINTED))) {
- config = kvm_pmu_ops.pmc_perf_hw_id(pmc);
+ config = static_call(kvm_x86_pmu_pmc_perf_hw_id)(pmc);
if (config != PERF_COUNT_HW_MAX)
type = PERF_TYPE_HARDWARE;
}
@@ -269,7 +275,7 @@ void reprogram_fixed_counter(struct kvm_pmc *pmc, u8 ctrl, int idx)

pmc->current_config = (u64)ctrl;
pmc_reprogram_counter(pmc, PERF_TYPE_HARDWARE,
- kvm_pmu_ops.pmc_perf_hw_id(pmc),
+ static_call(kvm_x86_pmu_pmc_perf_hw_id)(pmc),
!(en_field & 0x2), /* exclude user */
!(en_field & 0x1), /* exclude kernel */
pmi, false, false);
@@ -278,7 +284,7 @@ EXPORT_SYMBOL_GPL(reprogram_fixed_counter);

void reprogram_counter(struct kvm_pmu *pmu, int pmc_idx)
{
- struct kvm_pmc *pmc = kvm_pmu_ops.pmc_idx_to_pmc(pmu, pmc_idx);
+ struct kvm_pmc *pmc = static_call(kvm_x86_pmu_pmc_idx_to_pmc)(pmu, pmc_idx);

if (!pmc)
return;
@@ -300,7 +306,7 @@ void kvm_pmu_handle_event(struct kvm_vcpu *vcpu)
int bit;

for_each_set_bit(bit, pmu->reprogram_pmi, X86_PMC_IDX_MAX) {
- struct kvm_pmc *pmc = kvm_pmu_ops.pmc_idx_to_pmc(pmu, bit);
+ struct kvm_pmc *pmc = static_call(kvm_x86_pmu_pmc_idx_to_pmc)(pmu, bit);

if (unlikely(!pmc || !pmc->perf_event)) {
clear_bit(bit, pmu->reprogram_pmi);
@@ -322,7 +328,7 @@ void kvm_pmu_handle_event(struct kvm_vcpu *vcpu)
/* check if idx is a valid index to access PMU */
bool kvm_pmu_is_valid_rdpmc_ecx(struct kvm_vcpu *vcpu, unsigned int idx)
{
- return kvm_pmu_ops.is_valid_rdpmc_ecx(vcpu, idx);
+ return static_call(kvm_x86_pmu_is_valid_rdpmc_ecx)(vcpu, idx);
}

bool is_vmware_backdoor_pmc(u32 pmc_idx)
@@ -372,7 +378,7 @@ int kvm_pmu_rdpmc(struct kvm_vcpu *vcpu, unsigned idx, u64 *data)
if (is_vmware_backdoor_pmc(idx))
return kvm_pmu_rdpmc_vmware(vcpu, idx, data);

- pmc = kvm_pmu_ops.rdpmc_ecx_to_pmc(vcpu, idx, &mask);
+ pmc = static_call(kvm_x86_pmu_rdpmc_ecx_to_pmc)(vcpu, idx, &mask);
if (!pmc)
return 1;

@@ -388,22 +394,21 @@ int kvm_pmu_rdpmc(struct kvm_vcpu *vcpu, unsigned idx, u64 *data)
void kvm_pmu_deliver_pmi(struct kvm_vcpu *vcpu)
{
if (lapic_in_kernel(vcpu)) {
- if (kvm_pmu_ops.deliver_pmi)
- kvm_pmu_ops.deliver_pmi(vcpu);
+ static_call_cond(kvm_x86_pmu_deliver_pmi)(vcpu);
kvm_apic_local_deliver(vcpu->arch.apic, APIC_LVTPC);
}
}

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

static void kvm_pmu_mark_pmc_in_use(struct kvm_vcpu *vcpu, u32 msr)
{
struct kvm_pmu *pmu = vcpu_to_pmu(vcpu);
- struct kvm_pmc *pmc = kvm_pmu_ops.msr_idx_to_pmc(vcpu, msr);
+ struct kvm_pmc *pmc = static_call(kvm_x86_pmu_msr_idx_to_pmc)(vcpu, msr);

if (pmc)
__set_bit(pmc->idx, pmu->pmc_in_use);
@@ -411,13 +416,13 @@ static void kvm_pmu_mark_pmc_in_use(struct kvm_vcpu *vcpu, u32 msr)

int kvm_pmu_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
{
- return kvm_pmu_ops.get_msr(vcpu, msr_info);
+ return static_call(kvm_x86_pmu_get_msr)(vcpu, msr_info);
}

int kvm_pmu_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
{
kvm_pmu_mark_pmc_in_use(vcpu, msr_info->index);
- return kvm_pmu_ops.set_msr(vcpu, msr_info);
+ return static_call(kvm_x86_pmu_set_msr)(vcpu, msr_info);
}

/* refresh PMU settings. This function generally is called when underlying
@@ -426,7 +431,7 @@ int kvm_pmu_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
*/
void kvm_pmu_refresh(struct kvm_vcpu *vcpu)
{
- kvm_pmu_ops.refresh(vcpu);
+ static_call(kvm_x86_pmu_refresh)(vcpu);
}

void kvm_pmu_reset(struct kvm_vcpu *vcpu)
@@ -434,7 +439,7 @@ void kvm_pmu_reset(struct kvm_vcpu *vcpu)
struct kvm_pmu *pmu = vcpu_to_pmu(vcpu);

irq_work_sync(&pmu->irq_work);
- kvm_pmu_ops.reset(vcpu);
+ static_call(kvm_x86_pmu_reset)(vcpu);
}

void kvm_pmu_init(struct kvm_vcpu *vcpu)
@@ -442,7 +447,7 @@ void kvm_pmu_init(struct kvm_vcpu *vcpu)
struct kvm_pmu *pmu = vcpu_to_pmu(vcpu);

memset(pmu, 0, sizeof(*pmu));
- kvm_pmu_ops.init(vcpu);
+ static_call(kvm_x86_pmu_init)(vcpu);
init_irq_work(&pmu->irq_work, kvm_pmi_trigger_fn);
pmu->event_count = 0;
pmu->need_cleanup = false;
@@ -474,14 +479,13 @@ void kvm_pmu_cleanup(struct kvm_vcpu *vcpu)
pmu->pmc_in_use, X86_PMC_IDX_MAX);

for_each_set_bit(i, bitmask, X86_PMC_IDX_MAX) {
- pmc = kvm_pmu_ops.pmc_idx_to_pmc(pmu, i);
+ pmc = static_call(kvm_x86_pmu_pmc_idx_to_pmc)(pmu, i);

if (pmc && pmc->perf_event && !pmc_speculative_in_use(pmc))
pmc_stop_counter(pmc);
}

- if (kvm_pmu_ops.cleanup)
- kvm_pmu_ops.cleanup(vcpu);
+ static_call_cond(kvm_x86_pmu_cleanup)(vcpu);

bitmap_zero(pmu->pmc_in_use, X86_PMC_IDX_MAX);
}
@@ -511,7 +515,7 @@ static inline bool eventsel_match_perf_hw_id(struct kvm_pmc *pmc,
unsigned int config;

pmc->eventsel &= (ARCH_PERFMON_EVENTSEL_EVENT | ARCH_PERFMON_EVENTSEL_UMASK);
- config = kvm_pmu_ops.pmc_perf_hw_id(pmc);
+ config = static_call(kvm_x86_pmu_pmc_perf_hw_id)(pmc);
pmc->eventsel = old_eventsel;
return config == perf_hw_id;
}
@@ -539,7 +543,7 @@ void kvm_pmu_trigger_event(struct kvm_vcpu *vcpu, u64 perf_hw_id)
int i;

for_each_set_bit(i, pmu->all_valid_pmc_idx, X86_PMC_IDX_MAX) {
- pmc = kvm_pmu_ops.pmc_idx_to_pmc(pmu, i);
+ pmc = static_call(kvm_x86_pmu_pmc_idx_to_pmc)(pmu, i);

if (!pmc || !pmc_is_enabled(pmc) || !pmc_speculative_in_use(pmc))
continue;
diff --git a/arch/x86/kvm/pmu.h b/arch/x86/kvm/pmu.h
index 7032d3ebf8f4..9ccdfb4e838e 100644
--- a/arch/x86/kvm/pmu.h
+++ b/arch/x86/kvm/pmu.h
@@ -43,6 +43,11 @@ struct kvm_pmu_ops {
void (*cleanup)(struct kvm_vcpu *vcpu);
};

+#define KVM_X86_PMU_OP(func) \
+ DECLARE_STATIC_CALL(kvm_x86_pmu_##func, *(((struct kvm_pmu_ops *)0)->func));
+#define KVM_X86_PMU_OP_OPTIONAL KVM_X86_PMU_OP
+#include <asm/kvm-x86-pmu-ops.h>
+
static inline u64 pmc_bitmask(struct kvm_pmc *pmc)
{
struct kvm_pmu *pmu = pmc_to_pmu(pmc);
@@ -92,7 +97,7 @@ static inline bool pmc_is_fixed(struct kvm_pmc *pmc)

static inline bool pmc_is_enabled(struct kvm_pmc *pmc)
{
- return kvm_pmu_ops.pmc_is_enabled(pmc);
+ return static_call(kvm_x86_pmu_pmc_is_enabled)(pmc);
}

static inline bool kvm_valid_perf_global_ctrl(struct kvm_pmu *pmu,
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 0a76f7281e74..ffa0b219c13e 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -11519,6 +11519,14 @@ static inline void kvm_ops_static_call_update(void)
(void *)__static_call_return0);
#include <asm/kvm-x86-ops.h>
#undef __KVM_X86_OP
+
+#define __KVM_X86_PMU_OP(func) \
+ static_call_update(kvm_x86_pmu_##func, kvm_pmu_ops.func);
+#define KVM_X86_PMU_OP(func) \
+ WARN_ON(!kvm_pmu_ops.func); __KVM_X86_PMU_OP(func)
+#define KVM_X86_PMU_OP_OPTIONAL __KVM_X86_PMU_OP
+#include <asm/kvm-x86-pmu-ops.h>
+#undef __KVM_X86_PMU_OP
}

int kvm_arch_hardware_setup(void *opaque)
--
2.35.1

Next message: Arend van Spriel: "Re: ftrace bug"
Previous message: Like Xu: "[PATCH v3 3/4] KVM: x86: Move .pmu_ops to kvm_x86_init_ops and tag as __initdata"
In reply to: Like Xu: "[PATCH v3 3/4] KVM: x86: Move .pmu_ops to kvm_x86_init_ops and tag as __initdata"
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