Re: [PATCH 3/3] KVM: x86: Use static calls to reduce kvm_pmu_ops overhead

Like Xu <like.xu.linux@xxxxxxxxx> · Thu, 4 Nov 2021 16:14:13 +0800

On 3/11/2021 8:08 pm, Yao Yuan wrote:
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 ?

You may git squash all commits to get it *work*.

With reference to afaf0b2f9b801c6eb2278b52d49e6a7d7b659cf1[1],
doing one thing at a time will make things go smoother.

[1] 
https://lore.kernel.org/lkml/20200321202603.19355-7-sean.j.christopherson@xxxxxxxxx/


                             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








