From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6DA2CC282CE for ; Wed, 22 May 2019 16:26:17 +0000 (UTC) Received: from mm01.cs.columbia.edu (mm01.cs.columbia.edu [128.59.11.253]) by mail.kernel.org (Postfix) with ESMTP id F0F3E20675 for ; Wed, 22 May 2019 16:26:16 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org F0F3E20675 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvmarm-bounces@lists.cs.columbia.edu Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 6009D4A4A9; Wed, 22 May 2019 12:26:16 -0400 (EDT) X-Virus-Scanned: at lists.cs.columbia.edu Received: from mm01.cs.columbia.edu ([127.0.0.1]) by localhost (mm01.cs.columbia.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id kswj67RNeinu; Wed, 22 May 2019 12:26:15 -0400 (EDT) Received: from mm01.cs.columbia.edu (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 047C84A4AA; Wed, 22 May 2019 12:26:15 -0400 (EDT) Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 05BA44A4A4 for ; Wed, 22 May 2019 12:26:13 -0400 (EDT) X-Virus-Scanned: at lists.cs.columbia.edu Received: from mm01.cs.columbia.edu ([127.0.0.1]) by localhost (mm01.cs.columbia.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id vMFRzJUfYVNy for ; Wed, 22 May 2019 12:26:11 -0400 (EDT) Received: from foss.arm.com (usa-sjc-mx-foss1.foss.arm.com [217.140.101.70]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 90DC54A321 for ; Wed, 22 May 2019 12:26:11 -0400 (EDT) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 06EFF341; Wed, 22 May 2019 09:26:11 -0700 (PDT) Received: from localhost (unknown [10.37.6.20]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 93A4B3F5AF; Wed, 22 May 2019 09:26:10 -0700 (PDT) Date: Wed, 22 May 2019 17:26:08 +0100 From: Andrew Murray To: Marc Zyngier Subject: Re: [PATCH v8 5/6] KVM: arm/arm64: remove pmc->bitmask Message-ID: <20190522162608.GF8268@e119886-lin.cambridge.arm.com> References: <20190522153019.18645-1-andrew.murray@arm.com> <20190522153019.18645-6-andrew.murray@arm.com> <7f84fcac-ee73-d076-f0e3-3b214912daaf@arm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <7f84fcac-ee73-d076-f0e3-3b214912daaf@arm.com> User-Agent: Mutt/1.10.1+81 (426a6c1) (2018-08-26) Cc: kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org X-BeenThere: kvmarm@lists.cs.columbia.edu X-Mailman-Version: 2.1.14 Precedence: list List-Id: Where KVM/ARM decisions are made List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu On Wed, May 22, 2019 at 05:07:31PM +0100, Marc Zyngier wrote: > On 22/05/2019 16:30, Andrew Murray wrote: > > We currently use pmc->bitmask to determine the width of the pmc - however > > it's superfluous as the pmc index already describes if the pmc is a cycle > > counter or event counter. The architecture clearly describes the widths of > > these counters. > > > > Let's remove the bitmask to simplify the code. > > > > Signed-off-by: Andrew Murray > > --- > > include/kvm/arm_pmu.h | 1 - > > virt/kvm/arm/pmu.c | 15 +++++---------- > > 2 files changed, 5 insertions(+), 11 deletions(-) > > > > diff --git a/include/kvm/arm_pmu.h b/include/kvm/arm_pmu.h > > index b73f31baca52..2f0e28dc5a9e 100644 > > --- a/include/kvm/arm_pmu.h > > +++ b/include/kvm/arm_pmu.h > > @@ -28,7 +28,6 @@ > > struct kvm_pmc { > > u8 idx; /* index into the pmu->pmc array */ > > struct perf_event *perf_event; > > - u64 bitmask; > > }; > > > > struct kvm_pmu { > > diff --git a/virt/kvm/arm/pmu.c b/virt/kvm/arm/pmu.c > > index ae1e886d4a1a..c4e2bc213617 100644 > > --- a/virt/kvm/arm/pmu.c > > +++ b/virt/kvm/arm/pmu.c > > @@ -47,7 +47,10 @@ u64 kvm_pmu_get_counter_value(struct kvm_vcpu *vcpu, u64 select_idx) > > counter += perf_event_read_value(pmc->perf_event, &enabled, > > &running); > > > > - return counter & pmc->bitmask; > > + if (select_idx != ARMV8_PMU_CYCLE_IDX) > > + counter = lower_32_bits(counter); > > + > > + return counter; > > } > > > > /** > > @@ -113,7 +116,6 @@ void kvm_pmu_vcpu_reset(struct kvm_vcpu *vcpu) > > for (i = 0; i < ARMV8_PMU_MAX_COUNTERS; i++) { > > kvm_pmu_stop_counter(vcpu, &pmu->pmc[i]); > > pmu->pmc[i].idx = i; > > - pmu->pmc[i].bitmask = 0xffffffffUL; > > } > > } > > > > @@ -348,8 +350,6 @@ void kvm_pmu_software_increment(struct kvm_vcpu *vcpu, u64 val) > > */ > > void kvm_pmu_handle_pmcr(struct kvm_vcpu *vcpu, u64 val) > > { > > - struct kvm_pmu *pmu = &vcpu->arch.pmu; > > - struct kvm_pmc *pmc; > > u64 mask; > > int i; > > > > @@ -368,11 +368,6 @@ void kvm_pmu_handle_pmcr(struct kvm_vcpu *vcpu, u64 val) > > for (i = 0; i < ARMV8_PMU_CYCLE_IDX; i++) > > kvm_pmu_set_counter_value(vcpu, i, 0); > > } > > - > > - if (val & ARMV8_PMU_PMCR_LC) { > > - pmc = &pmu->pmc[ARMV8_PMU_CYCLE_IDX]; > > - pmc->bitmask = 0xffffffffffffffffUL; > > - } > > } > > > > static bool kvm_pmu_counter_is_enabled(struct kvm_vcpu *vcpu, u64 select_idx) > > @@ -420,7 +415,7 @@ static void kvm_pmu_create_perf_event(struct kvm_vcpu *vcpu, u64 select_idx) > > > > counter = kvm_pmu_get_counter_value(vcpu, select_idx); > > /* The initial sample period (overflow count) of an event. */ > > - attr.sample_period = (-counter) & pmc->bitmask; > > + attr.sample_period = (-counter) & GENMASK(31, 0); > > Isn't this the one case where the bitmask actually matters? If we're > dealing with the cycle counter, it shouldn't be truncated, right? Ah yes, that should be conditional on idx as well. Thanks, Andrew Murray > > > > > event = perf_event_create_kernel_counter(&attr, -1, current, > > kvm_pmu_perf_overflow, pmc); > > > > Thanks, > > M. > -- > Jazz is not dead. It just smells funny... _______________________________________________ kvmarm mailing list kvmarm@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/kvmarm