From nobody Fri Sep 12 13:32:59 2025 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 93E25C61DA4 for ; Fri, 10 Feb 2023 00:32:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230300AbjBJAc3 (ORCPT ); Thu, 9 Feb 2023 19:32:29 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53054 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230170AbjBJAcQ (ORCPT ); Thu, 9 Feb 2023 19:32:16 -0500 Received: from mail-pg1-x54a.google.com (mail-pg1-x54a.google.com [IPv6:2607:f8b0:4864:20::54a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7CB495CBF3 for ; Thu, 9 Feb 2023 16:32:02 -0800 (PST) Received: by mail-pg1-x54a.google.com with SMTP id x3-20020a654143000000b004f2f2dafb21so1760547pgp.0 for ; Thu, 09 Feb 2023 16:32:02 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:reply-to:from:to:cc:subject:date:message-id:reply-to; bh=qEyz/D/GwawmEFE6mKfSBe68GjnRayQfCebOkuONNBw=; b=keO5G55ZMsL2Z8lWgVdrwBdDX+uSCcf60tBA/h0bLFRFunQ5U8VPjAPDzH6pZORQWk nFQ43s7XYMOcxFPfMOg3Xlj5CCK96SCu9/R6aCyl0Tutl6y55A7r4BGMFVSaBcWI1POs A5azzTnHL/yjeNxWOjKh+hIu+eN4pZ9OrmUhNxyVeT7+aoSp5MdiX3CAIx+MP33eLvqj SKRAXmxKQbst1gty7eyX6ljXkIK+d1fVdqpcHC5Kj9TccjqvRPaN37oj0mxo0d+CAW1b +BJ5S4PwpjQn7P3pHtGLmZKEPafI+rpLBqKOJ732ZFzz/bQQUmeuDwAapEM4arLY9Jgx lUaA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:reply-to:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=qEyz/D/GwawmEFE6mKfSBe68GjnRayQfCebOkuONNBw=; b=goLZqqRjo13OOAJAO4WRj9ql5eeByQ6onndxW3noqx7H4w3G+m2X6xDEKwXCQf1MzN xcRqfVd8VVn4MWNV8g43wHSoaWl1I9Y+ZsmSajnnv9NW3vW7KfsrzAOLYw1FQlAA1Bwt oDxaMuSIj/QYD9Ran4EPc2P3Ur8x2fhK5EhMXYvrCIJkfrU2OR7WorwISmLu+njjhZ7r Edr3NHSqm0WOCME0Ss0cTvNptLlQGvBhAdHHvGrsi035PXCNnuMqJ8EE3QAYHEQObUtJ jrSy1vZ5YzEfMy4ljXYSpuLYMN96gKZvPwW1A0w+3Szqcfr1f6SmCaPuoncEa6igYzZE MrxQ== X-Gm-Message-State: AO0yUKWDn0nQ8Xq34kXwkzV3t03lKH4XLOLe7ivr8vz7TGkv5o8tXVjr suNfTLIcqwK95a+T0p7WYoDZsEt4Lww= X-Google-Smtp-Source: AK7set+Lg4llgEJ6QaiikJdamHYHEjb0MDTZ0zPakDnAXCfGtwwICr3RneW3uXmfczA4QmZz33KIBVoHPHo= X-Received: from zagreus.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:5c37]) (user=seanjc job=sendgmr) by 2002:a17:90b:1957:b0:230:9d9a:377d with SMTP id nk23-20020a17090b195700b002309d9a377dmr2128693pjb.102.1675989121567; Thu, 09 Feb 2023 16:32:01 -0800 (PST) Reply-To: Sean Christopherson Date: Fri, 10 Feb 2023 00:31:33 +0000 In-Reply-To: <20230210003148.2646712-1-seanjc@google.com> Mime-Version: 1.0 References: <20230210003148.2646712-1-seanjc@google.com> X-Mailer: git-send-email 2.39.1.581.gbfd45094c4-goog Message-ID: <20230210003148.2646712-7-seanjc@google.com> Subject: [PATCH v2 06/21] KVM: x86/pmu: WARN and bug the VM if PMU is refreshed after vCPU has run From: Sean Christopherson To: Sean Christopherson , Paolo Bonzini Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Xiaoyao Li , Like Xu Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Now that KVM disallows changing feature MSRs, i.e. PERF_CAPABILITIES, after running a vCPU, WARN and bug the VM if the PMU is refreshed after the vCPU has run. Note, KVM has disallowed CPUID updates after running a vCPU since commit feb627e8d6f6 ("KVM: x86: Forbid KVM_SET_CPUID{,2} after KVM_RUN"), i.e. PERF_CAPABILITIES was the only remaining way to trigger a PMU refresh after KVM_RUN. Cc: Like Xu Signed-off-by: Sean Christopherson --- arch/x86/kvm/pmu.c | 3 +++ arch/x86/kvm/x86.c | 10 +++++++++- 2 files changed, 12 insertions(+), 1 deletion(-) diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c index 612e6c70ce2e..7e974c4e61b0 100644 --- a/arch/x86/kvm/pmu.c +++ b/arch/x86/kvm/pmu.c @@ -589,6 +589,9 @@ int kvm_pmu_set_msr(struct kvm_vcpu *vcpu, struct msr_d= ata *msr_info) */ void kvm_pmu_refresh(struct kvm_vcpu *vcpu) { + if (KVM_BUG_ON(kvm_vcpu_has_run(vcpu), vcpu->kvm)) + return; + static_call(kvm_x86_pmu_refresh)(vcpu); } =20 diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 186cb6a81643..1b14632a94a3 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -3626,9 +3626,17 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct= msr_data *msr_info) if (data & ~kvm_caps.supported_perf_cap) return 1; =20 + /* + * Note, this is not just a performance optimization! KVM + * disallows changing feature MSRs after the vCPU has run; PMU + * refresh will bug the VM if called after the vCPU has run. + */ + if (vcpu->arch.perf_capabilities =3D=3D data) + break; + vcpu->arch.perf_capabilities =3D data; kvm_pmu_refresh(vcpu); - return 0; + break; case MSR_EFER: return set_efer(vcpu, msr_info); case MSR_K7_HWCR: --=20 2.39.1.581.gbfd45094c4-goog