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=-14.0 required=3.0 tests=BAYES_00,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=unavailable 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 8B8EBC433E0 for ; Wed, 3 Feb 2021 10:33:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 484A864F58 for ; Wed, 3 Feb 2021 10:33:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233831AbhBCKdA (ORCPT ); Wed, 3 Feb 2021 05:33:00 -0500 Received: from mail.kernel.org ([198.145.29.99]:54264 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233548AbhBCKc6 (ORCPT ); Wed, 3 Feb 2021 05:32:58 -0500 Received: from disco-boy.misterjones.org (disco-boy.misterjones.org [51.254.78.96]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 2B55764E0A; Wed, 3 Feb 2021 10:32:17 +0000 (UTC) Received: from disco-boy.misterjones.org ([51.254.78.96] helo=www.loen.fr) by disco-boy.misterjones.org with esmtpsa (TLS1.2) tls TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 (Exim 4.94) (envelope-from ) id 1l7FSH-00Bj22-Up; Wed, 03 Feb 2021 10:32:14 +0000 MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit Date: Wed, 03 Feb 2021 10:32:13 +0000 From: Marc Zyngier To: Alexandru Elisei Cc: linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org, James Morse , Julien Thierry , Suzuki K Poulose , Eric Auger , kernel-team@android.com Subject: Re: [PATCH v2 6/7] KVM: arm64: Upgrade PMU support to ARMv8.4 In-Reply-To: <680c2e4f-cc9f-10c1-1158-7de32057fb0d@arm.com> References: <20210125122638.2947058-1-maz@kernel.org> <20210125122638.2947058-7-maz@kernel.org> <680c2e4f-cc9f-10c1-1158-7de32057fb0d@arm.com> User-Agent: Roundcube Webmail/1.4.10 Message-ID: <20c1d805997523ae04f45be90fb4dd1a@kernel.org> X-Sender: maz@kernel.org X-SA-Exim-Connect-IP: 51.254.78.96 X-SA-Exim-Rcpt-To: alexandru.elisei@arm.com, linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org, james.morse@arm.com, julien.thierry.kdev@gmail.com, suzuki.poulose@arm.com, eric.auger@redhat.com, kernel-team@android.com X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On 2021-01-27 17:41, Alexandru Elisei wrote: > Hi Marc, > > Had another look at the patch, comments below. > > On 1/25/21 12:26 PM, Marc Zyngier wrote: >> Upgrading the PMU code from ARMv8.1 to ARMv8.4 turns out to be >> pretty easy. All that is required is support for PMMIR_EL1, which >> is read-only, and for which returning 0 is a valid option as long >> as we don't advertise STALL_SLOT as an implemented event. >> >> Let's just do that and adjust what we return to the guest. >> >> Signed-off-by: Marc Zyngier >> --- >> arch/arm64/include/asm/sysreg.h | 3 +++ >> arch/arm64/kvm/pmu-emul.c | 6 ++++++ >> arch/arm64/kvm/sys_regs.c | 11 +++++++---- >> 3 files changed, 16 insertions(+), 4 deletions(-) >> >> diff --git a/arch/arm64/include/asm/sysreg.h >> b/arch/arm64/include/asm/sysreg.h >> index 8b5e7e5c3cc8..2fb3f386588c 100644 >> --- a/arch/arm64/include/asm/sysreg.h >> +++ b/arch/arm64/include/asm/sysreg.h >> @@ -846,7 +846,10 @@ >> >> #define ID_DFR0_PERFMON_SHIFT 24 >> >> +#define ID_DFR0_PERFMON_8_0 0x3 >> #define ID_DFR0_PERFMON_8_1 0x4 >> +#define ID_DFR0_PERFMON_8_4 0x5 >> +#define ID_DFR0_PERFMON_8_5 0x6 >> >> #define ID_ISAR4_SWP_FRAC_SHIFT 28 >> #define ID_ISAR4_PSR_M_SHIFT 24 >> diff --git a/arch/arm64/kvm/pmu-emul.c b/arch/arm64/kvm/pmu-emul.c >> index 398f6df1bbe4..72cd704a8368 100644 >> --- a/arch/arm64/kvm/pmu-emul.c >> +++ b/arch/arm64/kvm/pmu-emul.c >> @@ -795,6 +795,12 @@ u64 kvm_pmu_get_pmceid(struct kvm_vcpu *vcpu, >> bool pmceid1) >> base = 0; >> } else { >> val = read_sysreg(pmceid1_el0); >> + /* >> + * Don't advertise STALL_SLOT, as PMMIR_EL0 is handled >> + * as RAZ >> + */ >> + if (vcpu->kvm->arch.pmuver >= ID_AA64DFR0_PMUVER_8_4) >> + val &= ~BIT_ULL(ARMV8_PMUV3_PERFCTR_STALL_SLOT - 32); > > This is confusing the me. We have kvm->arch.pmuver set to the hardware > PMU version > (as set by __armv8pmu_probe_pmu()), but we ignore it when reporting the > PMU > version to the guest. Why do we do that? We limit the event number in > kvm_pmu_event_mask() based on the hardware PMU version, so even if we > advertise > Armv8.4 PMU, support for all those extra events added by Arm8.1 PMU is > missing (I hope I understood the code correctly). That's a bit of mess-up. We obtain ID_AA64DFR0_EL1 from the sanitised regs, but do most of our handling based on kvm->arch.pmuver. They really should be the same, because that's what the sanitised registers give you. As for the events themselves, I don't get your drift. We do support all the ARMv8.1 PMU events as long as the HW supports it, and we don't lie to the guest about it either (cpuid_feature_cap_perfmon_field does *cap* the field to some value, it doesn't allow it to increase past what the HW supports). > I looked at commit c854188ea010 ("KVM: arm64: limit PMU version to > PMUv3 for > ARMv8.1") which changed read_id_reg() to report PMUv3 for Armv8.1 > unconditionally, > and there's no explanation why PMUv3 for Armv8.1 was chosen instead of > plain PMUv3 (PMUVer = 0b0100). We picked ARMv8.1 because this is the first PMU revision that gives you events in the 0x4000 range, all of which are available on common ARMv8.2 HW. Thanks, M. -- Jazz is not dead. It just smells funny...