From mboxrd@z Thu Jan 1 00:00:00 1970 From: Suzuki K Poulose Subject: Re: [PATCH v2 3/5] KVM: arm/arm64: re-create event when setting counter value Date: Wed, 13 Feb 2019 14:28:51 +0000 Message-ID: <3adc7d31-9d5a-d66b-21ee-9b4da986d24f@arm.com> References: <1549299218-44714-1-git-send-email-andrew.murray@arm.com> <1549299218-44714-4-git-send-email-andrew.murray@arm.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1549299218-44714-4-git-send-email-andrew.murray@arm.com> Content-Language: en-US List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=m.gmane.org@lists.infradead.org To: andrew.murray@arm.com, christoffer.dall@arm.com, marc.zyngier@arm.com Cc: kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org, julien.thierry@arm.com List-Id: kvmarm@lists.cs.columbia.edu Hi Andrew, On 04/02/2019 16:53, Andrew Murray wrote: > The perf event sample_period is currently set based upon the current > counter value, when PMXEVTYPER is written to and the perf event is created. > However the user may choose to write the type before the counter value in > which case sample_period will be set incorrectly. Let's instead decouple > event creation from PMXEVTYPER and (re)create the event in either > suitation. > > Signed-off-by: Andrew Murray > --- > virt/kvm/arm/pmu.c | 40 +++++++++++++++++++++++++++++++--------- > 1 file changed, 31 insertions(+), 9 deletions(-) > > diff --git a/virt/kvm/arm/pmu.c b/virt/kvm/arm/pmu.c > index 6e7c179..95d74ec 100644 > --- a/virt/kvm/arm/pmu.c > +++ b/virt/kvm/arm/pmu.c > @@ -24,6 +24,7 @@ > #include > #include > > +static void kvm_pmu_create_perf_event(struct kvm_vcpu *vcpu, u64 select_idx); > /** > * kvm_pmu_get_counter_value - get PMU counter value > * @vcpu: The vcpu pointer > @@ -62,6 +63,9 @@ void kvm_pmu_set_counter_value(struct kvm_vcpu *vcpu, u64 select_idx, u64 val) > reg = (select_idx == ARMV8_PMU_CYCLE_IDX) > ? PMCCNTR_EL0 : PMEVCNTR0_EL0 + select_idx; > __vcpu_sys_reg(vcpu, reg) += (s64)val - kvm_pmu_get_counter_value(vcpu, select_idx); > + > + /* Recreate the perf event to reflect the updated sample_period */ > + kvm_pmu_create_perf_event(vcpu, select_idx); > } > > /** > @@ -378,23 +382,22 @@ static bool kvm_pmu_counter_is_enabled(struct kvm_vcpu *vcpu, u64 select_idx) > } > > /** > - * kvm_pmu_set_counter_event_type - set selected counter to monitor some event > + * kvm_pmu_create_perf_event - create a perf event for a counter > * @vcpu: The vcpu pointer > - * @data: The data guest writes to PMXEVTYPER_EL0 > + * @data: Type of event as per PMXEVTYPER_EL0 format > * @select_idx: The number of selected counter nit: data no longer exists. > - * > - * When OS accesses PMXEVTYPER_EL0, that means it wants to set a PMC to count an > - * event with given hardware event number. Here we call perf_event API to > - * emulate this action and create a kernel perf event for it. > */ > -void kvm_pmu_set_counter_event_type(struct kvm_vcpu *vcpu, u64 data, > - u64 select_idx) > +static void kvm_pmu_create_perf_event(struct kvm_vcpu *vcpu, u64 select_idx) > { With the comment from Julien addressed, Reviewed-by: Suzuki K Poulose