Re: [PATCH 2/5] KVM: x86/pmu: Add a helper to check if pmc has PEBS mode enabled

Sean Christopherson
2023-05-24T20:54:35Z

On Fri, Mar 10, 2023, Like Xu wrote:
> From: Like Xu <likexu@tencent.com>
>
> Add a helper to check if pmc has PEBS mode enabled so that more new
> code may reuse this part and opportunistically drop a pmu reference.
>
> No functional change intended.
>
> Signed-off-by: Like Xu <likexu@tencent.com>
> ---
> arch/x86/kvm/pmu.c | 3 +--
> arch/x86/kvm/pmu.h | 7 +++++++
> 2 files changed, 8 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c
> index d1c89a6625a0..01a6b7ffa9b1 100644
> --- a/arch/x86/kvm/pmu.c
> +++ b/arch/x86/kvm/pmu.c
> @@ -191,7 +191,6 @@ static int pmc_reprogram_counter(struct kvm_pmc *pmc, u32 type, u64 config,
> bool exclude_user, bool exclude_kernel,
> bool intr)
> {
> - struct kvm_pmu *pmu = pmc_to_pmu(pmc);
> struct perf_event *event;
> struct perf_event_attr attr = {
> .type = type,
> @@ -203,7 +202,7 @@ static int pmc_reprogram_counter(struct kvm_pmc *pmc, u32 type, u64 config,
> .exclude_kernel = exclude_kernel,
> .config = config,
> };
> - bool pebs = test_bit(pmc->idx, (unsigned long *)&pmu->pebs_enable);
> + bool pebs = pebs_is_enabled(pmc);
>
> attr.sample_period = get_sample_period(pmc, pmc->counter);
>
> diff --git a/arch/x86/kvm/pmu.h b/arch/x86/kvm/pmu.h
> index cff0651b030b..db4262fe8814 100644
> --- a/arch/x86/kvm/pmu.h
> +++ b/arch/x86/kvm/pmu.h
> @@ -189,6 +189,13 @@ static inline void kvm_pmu_request_counter_reprogram(struct kvm_pmc *pmc)
> kvm_make_request(KVM_REQ_PMU, pmc->vcpu);
> }
>
> +static inline bool pebs_is_enabled(struct kvm_pmc *pmc)

pebs_is_enabled() is a bit too generic, e.g. at a glance I would expect it to return
true if PEBS as a whole is enabled. What about something like pmc_is_pebs() or
pmc_is_pebs_enabled()?