Re: [PATCH 3/3] KVM: x86: Use static calls to reduce kvm_pmu_ops overhead
From: Yao Yuan
Date: Wed Nov 03 2021 - 08:09:15 EST
On Wed, Nov 03, 2021 at 03:03:10PM +0800, Like Xu wrote:
> Convert kvm_pmu_ops to use static calls.
>
> Here are the worst sched_clock() nanosecond 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 | 10946 | 10047 (8%)
> .pmc_is_enabled | 11291 | 11175 (1%)
> .msr_idx_to_pmc | 13526 | 12346 (8%)
> .is_valid_msr | 10895 | 10484 (3%)
>
> Signed-off-by: Like Xu <likexu@xxxxxxxxxxx>
> ---
> arch/x86/kvm/pmu.c | 36 +++++++++++++++++-------------------
> arch/x86/kvm/pmu.h | 2 +-
> arch/x86/kvm/vmx/nested.c | 2 +-
> arch/x86/kvm/x86.c | 4 +++-
> 4 files changed, 22 insertions(+), 22 deletions(-)
>
> diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c
> index b6f08c719125..193f925e2064 100644
> --- a/arch/x86/kvm/pmu.c
> +++ b/arch/x86/kvm/pmu.c
> @@ -224,7 +224,7 @@ 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.find_arch_event(pmc_to_pmu(pmc),
> + config = static_call(kvm_x86_pmu_find_arch_event)(pmc_to_pmu(pmc),
Why you need change them into kvm_pmu_ops.XXX then convert
them into static call ? Move the instance definition of
kvm_pmu_ops from patch 1 into patch 3 and then drop patch 1,
will this work ?
> event_select,
> unit_mask);
> if (config != PERF_COUNT_HW_MAX)
> @@ -278,7 +278,7 @@ 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.find_fixed_event(idx),
> + static_call(kvm_x86_pmu_find_fixed_event)(idx),
> !(en_field & 0x2), /* exclude user */
> !(en_field & 0x1), /* exclude kernel */
> pmi, false, false);
> @@ -287,7 +287,7 @@ 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;
> @@ -309,7 +309,7 @@ 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);
> @@ -331,7 +331,7 @@ void kvm_pmu_handle_event(struct kvm_vcpu *vcpu)
> /* check if idx is a valid index to access PMU */
> int 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)
> @@ -381,7 +381,7 @@ 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;
>
> @@ -397,22 +397,21 @@ 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);
> @@ -420,13 +419,13 @@ 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
> @@ -435,7 +434,7 @@ 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)
> @@ -443,7 +442,7 @@ 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)
> @@ -451,7 +450,7 @@ 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;
> @@ -483,14 +482,13 @@ 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);
> }
> diff --git a/arch/x86/kvm/pmu.h b/arch/x86/kvm/pmu.h
> index e5550d4acf14..1818d1371ece 100644
> --- a/arch/x86/kvm/pmu.h
> +++ b/arch/x86/kvm/pmu.h
> @@ -109,7 +109,7 @@ 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/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
> index 1e793e44b5ff..a61661de1f39 100644
> --- a/arch/x86/kvm/vmx/nested.c
> +++ b/arch/x86/kvm/vmx/nested.c
> @@ -4796,7 +4796,7 @@ void nested_vmx_pmu_entry_exit_ctls_update(struct kvm_vcpu *vcpu)
> return;
>
> vmx = to_vmx(vcpu);
> - if (kvm_pmu_ops.is_valid_msr(vcpu, MSR_CORE_PERF_GLOBAL_CTRL)) {
> + if (static_call(kvm_x86_pmu_is_valid_msr)(vcpu, MSR_CORE_PERF_GLOBAL_CTRL)) {
> vmx->nested.msrs.entry_ctls_high |=
> VM_ENTRY_LOAD_IA32_PERF_GLOBAL_CTRL;
> vmx->nested.msrs.exit_ctls_high |=
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 72d286595012..88a3ef809c98 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -11317,8 +11317,10 @@ int kvm_arch_hardware_setup(void *opaque)
> memcpy(&kvm_x86_ops, ops->runtime_ops, sizeof(kvm_x86_ops));
> kvm_ops_static_call_update();
>
> - if (kvm_x86_ops.hardware_enable)
> + if (kvm_x86_ops.hardware_enable) {
> memcpy(&kvm_pmu_ops, kvm_x86_ops.pmu_ops, sizeof(kvm_pmu_ops));
> + kvm_pmu_ops_static_call_update();
> + }
>
> if (!kvm_cpu_cap_has(X86_FEATURE_XSAVES))
> supported_xss = 0;
> --
> 2.33.0
>