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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9906EC3DA7D for ; Tue, 3 Jan 2023 12:40:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231249AbjACMkk (ORCPT ); Tue, 3 Jan 2023 07:40:40 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36148 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230193AbjACMkj (ORCPT ); Tue, 3 Jan 2023 07:40:39 -0500 Received: from frasgout.his.huawei.com (frasgout.his.huawei.com [185.176.79.56]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9A2F263BA for ; Tue, 3 Jan 2023 04:40:38 -0800 (PST) Received: from lhrpeml500005.china.huawei.com (unknown [172.18.147.207]) by frasgout.his.huawei.com (SkyGuard) with ESMTP id 4NmXJr05nbz6HJj0; Tue, 3 Jan 2023 20:35:55 +0800 (CST) Received: from localhost (10.202.227.76) by lhrpeml500005.china.huawei.com (7.191.163.240) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.34; Tue, 3 Jan 2023 12:40:34 +0000 Date: Tue, 3 Jan 2023 12:40:34 +0000 From: Jonathan Cameron To: Reiji Watanabe CC: Marc Zyngier , , , , , James Morse , Alexandru Elisei , Suzuki K Poulose , Paolo Bonzini , "Ricardo Koller" , Oliver Upton , "Jing Zhang" , Raghavendra Rao Anata Subject: Re: [PATCH 0/7] KVM: arm64: PMU: Allow userspace to limit the number of PMCs on vCPU Message-ID: <20230103124034.000027aa@Huawei.com> In-Reply-To: <20221230035928.3423990-1-reijiw@google.com> References: <20221230035928.3423990-1-reijiw@google.com> Organization: Huawei Technologies Research and Development (UK) Ltd. X-Mailer: Claws Mail 4.1.0 (GTK 3.24.33; x86_64-w64-mingw32) MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.202.227.76] X-ClientProxiedBy: lhrpeml100003.china.huawei.com (7.191.160.210) To lhrpeml500005.china.huawei.com (7.191.163.240) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Thu, 29 Dec 2022 19:59:21 -0800 Reiji Watanabe wrote: > The goal of this series is to allow userspace to limit the number > of PMU event counters on the vCPU. Hi Rieji, Why do you want to do this? I can conjecture a bunch of possible reasons, but they may not match up with your use case. It would be useful to have that information in the cover letter. Jonathan > > The number of PMU event counters is indicated in PMCR_EL0.N. > For a vCPU with PMUv3 configured, its value will be the same as > the host value by default. Userspace can set PMCR_EL0.N for the > vCPU to a lower value than the host value, using KVM_SET_ONE_REG. > However, it is practically unsupported, as KVM resets PMCR_EL0.N > to the host value on vCPU reset and some KVM code uses the host > value to identify (un)implemented event counters on the vCPU. > > This series will ensure that the PMCR_EL0.N value is preserved > on vCPU reset and that KVM doesn't use the host value > to identify (un)implemented event counters on the vCPU. > This allows userspace to limit the number of the PMU event > counters on the vCPU. > > Patch 1 fixes reset_pmu_reg() to ensure that (RAZ) bits of > {PMCNTEN,PMOVS}{SET,CLR}_EL1 corresponding to unimplemented event > counters on the vCPU are reset to zero even when PMCR_EL0.N for > the vCPU is different from the host. > > Patch 2 is a minor refactoring to use the default PMU register reset > function (reset_pmu_reg()) for PMUSERENR_EL0 and PMCCFILTR_EL0. > (With the Patch 1 change, reset_pmu_reg() can now be used for > those registers) > > Patch 3 fixes reset_pmcr() to preserve PMCR_EL0.N for the vCPU on > vCPU reset. > > Patch 4-7 adds a selftest to verify reading and writing PMU registers > for implemented or unimplemented PMU event counters on the vCPU. > > The series is based on kvmarm/fixes at the following commit: > commit aff234839f8b ("KVM: arm64: PMU: Fix PMCR_EL0 reset value") > > Reiji Watanabe (7): > KVM: arm64: PMU: Have reset_pmu_reg() to clear a register > KVM: arm64: PMU: Use reset_pmu_reg() for PMUSERENR_EL0 and > PMCCFILTR_EL0 > KVM: arm64: PMU: Preserve vCPU's PMCR_EL0.N value on vCPU reset > tools: arm64: Import perf_event.h > KVM: selftests: aarch64: Introduce vpmu_counter_access test > KVM: selftests: aarch64: vPMU register test for implemented counters > KVM: selftests: aarch64: vPMU register test for unimplemented counters > > arch/arm64/kvm/pmu-emul.c | 6 + > arch/arm64/kvm/sys_regs.c | 18 +- > tools/arch/arm64/include/asm/perf_event.h | 258 ++++++++ > tools/testing/selftests/kvm/.gitignore | 1 + > tools/testing/selftests/kvm/Makefile | 1 + > .../kvm/aarch64/vpmu_counter_access.c | 613 ++++++++++++++++++ > .../selftests/kvm/include/aarch64/processor.h | 1 + > 7 files changed, 886 insertions(+), 12 deletions(-) > create mode 100644 tools/arch/arm64/include/asm/perf_event.h > create mode 100644 tools/testing/selftests/kvm/aarch64/vpmu_counter_access.c > > > base-commit: aff234839f8b80ac101e6c2f14d0e44b236efa48