Messages in this thread | | | Date | Thu, 9 Dec 2021 20:50:12 +0800 | Subject | Re: [PATCH v2 6/7] KVM: x86: Introduce definitions to support static calls for kvm_pmu_ops | From | Like Xu <> |
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Hi Sean,
On 9/12/2021 2:35 am, Sean Christopherson wrote: > On Mon, Nov 08, 2021, Like Xu wrote: >> From: Like Xu <likexu@tencent.com> >> >> 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. >> >> Like what we did for kvm_x86_ops, 'pmu_ops' can be covered by >> static calls in a simlilar manner for insignificant but not >> negligible performance impact, especially on older models. >> >> Signed-off-by: Like Xu <likexu@tencent.com> >> --- > > This absolutely shouldn't be separated from patch 7/7. By _defining_ the static > calls but not providing the logic to actually _update_ the calls, it's entirely > possible to add static_call() invocations that will compile cleanly without any > chance of doing the right thing at runtime. > > diff --git a/arch/x86/kvm/pmu.h b/arch/x86/kvm/pmu.h > index 0236c1a953d0..804f98b5552e 100644 > --- a/arch/x86/kvm/pmu.h > +++ b/arch/x86/kvm/pmu.h > @@ -99,7 +99,7 @@ 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, > >> @@ -0,0 +1,32 @@ >> +/* SPDX-License-Identifier: GPL-2.0 */ >> +#if !defined(KVM_X86_PMU_OP) || !defined(KVM_X86_PMU_OP_NULL) >> +BUILD_BUG_ON(1) >> +#endif >> + >> +/* >> + * KVM_X86_PMU_OP() and KVM_X86_PMU_OP_NULL() are used to > > Please use all 80 chars. > >> + * help generate "static_call()"s. They are also intended for use when defining >> + * the amd/intel KVM_X86_PMU_OPs. KVM_X86_PMU_OP() can be used > > AMD/Intel since this is referring to the vendor and not to function names (like > the below reference). > >> + * for those functions that follow the [amd|intel]_func_name convention. >> + * KVM_X86_PMU_OP_NULL() can leave a NULL definition for the > > As below, please drop the _NULL() variant. > >> + * case where there is no definition or a function name that >> + * doesn't match the typical naming convention is supplied. >> + */ > > ... > >> diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c >> index 353989bf0102..bfdd9f2bc0fa 100644 >> --- a/arch/x86/kvm/pmu.c >> +++ b/arch/x86/kvm/pmu.c >> @@ -50,6 +50,12 @@ >> struct kvm_pmu_ops kvm_pmu_ops __read_mostly; >> EXPORT_SYMBOL_GPL(kvm_pmu_ops); >> >> +#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_NULL 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); >> diff --git a/arch/x86/kvm/pmu.h b/arch/x86/kvm/pmu.h >> index b2fe135d395a..40e0b523637b 100644 >> --- a/arch/x86/kvm/pmu.h >> +++ b/arch/x86/kvm/pmu.h >> @@ -45,6 +45,11 @@ 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_NULL KVM_X86_PMU_OP > > I don't want to proliferate the pointless and bitrot-prone KVM_X86_OP_NULL macro, > just omit this. I'll send a patch to drop KVM_X86_OP_NULL.
Thanks for your clear comments on this patch set.
I will send out V3 once KVM_X86_OP_NULL is dropped as well as the comment in arch/x86/include/asm/kvm-x86-ops.h is updated.
> >> +#include <asm/kvm-x86-pmu-ops.h> >> + >> static inline u64 pmc_bitmask(struct kvm_pmc *pmc) >> { >> struct kvm_pmu *pmu = pmc_to_pmu(pmc); >> -- >> 2.33.0 >> >
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