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([2001:b07:6468:f312:ec41:5e57:ff4d:8e51]) by smtp.gmail.com with ESMTPSA id a16sm7491633wrx.87.2020.02.21.23.34.38 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 21 Feb 2020 23:34:39 -0800 (PST) Subject: Re: [PATCH] KVM: x86: Adjust counter sample period after a wrmsr To: Eric Hankland , Jim Mattson , Peter Shier Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org References: <20200222023413.78202-1-ehankland@google.com> From: Paolo Bonzini Message-ID: <9adcb973-7b60-71dd-636d-1e451e664c55@redhat.com> Date: Sat, 22 Feb 2020 08:34:38 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.1.1 MIME-Version: 1.0 In-Reply-To: <20200222023413.78202-1-ehankland@google.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 22/02/20 03:34, Eric Hankland wrote: > The sample_period of a counter tracks when that counter will > overflow and set global status/trigger a PMI. However this currently > only gets set when the initial counter is created or when a counter is > resumed; this updates the sample period after a wrmsr so running > counters will accurately reflect their new value. > > Signed-off-by: Eric Hankland > --- > arch/x86/kvm/pmu.c | 4 ++-- > arch/x86/kvm/pmu.h | 8 ++++++++ > arch/x86/kvm/vmx/pmu_intel.c | 6 ++++++ > 3 files changed, 16 insertions(+), 2 deletions(-) > > diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c > index bcc6a73d6628..d1f8ca57d354 100644 > --- a/arch/x86/kvm/pmu.c > +++ b/arch/x86/kvm/pmu.c > @@ -111,7 +111,7 @@ static void pmc_reprogram_counter(struct kvm_pmc *pmc, u32 type, > .config = config, > }; > > - attr.sample_period = (-pmc->counter) & pmc_bitmask(pmc); > + attr.sample_period = get_sample_period(pmc, pmc->counter); > > if (in_tx) > attr.config |= HSW_IN_TX; > @@ -158,7 +158,7 @@ static bool pmc_resume_counter(struct kvm_pmc *pmc) > > /* recalibrate sample period and check if it's accepted by perf core */ > if (perf_event_period(pmc->perf_event, > - (-pmc->counter) & pmc_bitmask(pmc))) > + get_sample_period(pmc, pmc->counter))) > return false; > > /* reuse perf_event to serve as pmc_reprogram_counter() does*/ > diff --git a/arch/x86/kvm/pmu.h b/arch/x86/kvm/pmu.h > index 13332984b6d5..354b8598b6c1 100644 > --- a/arch/x86/kvm/pmu.h > +++ b/arch/x86/kvm/pmu.h > @@ -129,6 +129,15 @@ static inline struct kvm_pmc *get_fixed_pmc(struct kvm_pmu *pmu, u32 msr) > return NULL; > } > > +static inline u64 get_sample_period(struct kvm_pmc *pmc, u64 counter_value) > +{ > + u64 sample_period = (-counter_value) & pmc_bitmask(pmc); > + > + if (!sample_period) > + sample_period = pmc_bitmask(pmc) + 1; > + return sample_period; > +} > + > void reprogram_gp_counter(struct kvm_pmc *pmc, u64 eventsel); > void reprogram_fixed_counter(struct kvm_pmc *pmc, u8 ctrl, int fixed_idx); > void reprogram_counter(struct kvm_pmu *pmu, int pmc_idx); > diff --git a/arch/x86/kvm/vmx/pmu_intel.c b/arch/x86/kvm/vmx/pmu_intel.c > index fd21cdb10b79..e933541751fb 100644 > --- a/arch/x86/kvm/vmx/pmu_intel.c > +++ b/arch/x86/kvm/vmx/pmu_intel.c > @@ -263,9 +263,15 @@ static int intel_pmu_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info) > if (!msr_info->host_initiated) > data = (s64)(s32)data; > pmc->counter += data - pmc_read_counter(pmc); > + if (pmc->perf_event) > + perf_event_period(pmc->perf_event, > + get_sample_period(pmc, data)); > return 0; > } else if ((pmc = get_fixed_pmc(pmu, msr))) { > pmc->counter += data - pmc_read_counter(pmc); > + if (pmc->perf_event) > + perf_event_period(pmc->perf_event, > + get_sample_period(pmc, data)); > return 0; > } else if ((pmc = get_gp_pmc(pmu, msr, MSR_P6_EVNTSEL0))) { > if (data == pmc->eventsel) > Queued, thanks. Paolo