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=-6.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 89B0AC433FB for ; Mon, 29 Mar 2021 08:55:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 650D861919 for ; Mon, 29 Mar 2021 08:55:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235105AbhC2IzA (ORCPT ); Mon, 29 Mar 2021 04:55:00 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:44552 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236177AbhC2Iw5 (ORCPT ); Mon, 29 Mar 2021 04:52:57 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1617007976; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=Ow3OA1zz0sZgFQjgYK1itMYGQWEYDycsctQNZitiGSo=; b=Go+AeN+SgywL8g8xaKHZ4gB5mM5Po1482n/dM70mL2gIikvaVOW4hA56fT5+80wSWyhB8P yJxwZ+LS3ivFLEoDuVU14ZgYLTqS0bdudigvJnEuZ/gDp7SGSKtaYgaILLAnCoeFIlkcbx UnxgLmpzDRTD4eLrT2Olqv/BCdHIFY0= Received: from mail-wm1-f70.google.com (mail-wm1-f70.google.com [209.85.128.70]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-197-_uefPF8WNvOx4cEMeZQ5kQ-1; Mon, 29 Mar 2021 04:52:54 -0400 X-MC-Unique: _uefPF8WNvOx4cEMeZQ5kQ-1 Received: by mail-wm1-f70.google.com with SMTP id k132so1355666wma.1 for ; Mon, 29 Mar 2021 01:52:54 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:in-reply-to:references:date :message-id:mime-version; bh=Ow3OA1zz0sZgFQjgYK1itMYGQWEYDycsctQNZitiGSo=; b=iFNb74u70MvoK8uHR+9sRgWAI/7s92Dd1egpbOS7YZLddV7Hphf6fyo0TzehUL6sTq Lf4bk23dfXgHWJpw72fn94bj6PECE7/7jA99VCje90e7Jk9y25ILXQ1YF09JAlvEkuK+ JtsiNFtQYk2SBg9UgpuO2ODSevb8bSMnYUvlG7XMQieAo4iPNPOjoxUVR8DeW6BbD5sT II5ChVehy1nOJa6HOgTcbWA/YgxPhB2vzrjWq+vyTDSV70zg7zazuzsyNuhU2S8Te2LV VIE2v5XslOEAI3EQRbP9xQm0KsZ2ocIIvOP7FQvCnpBMDiDW5wMlVZUHbXE6mqdjzC9n amOA== X-Gm-Message-State: AOAM531gaLKozdt5aDiSnt4oMlVA/YLQGTCrZrRUjVslKOhOZi6IchQx LwSxk28dsGi+wC7VRxWNTzASenKpJgaBtuldIo9ZAPYGgsKeTZReLH/ukE/NLdNZKKg5hP/0e9B Af/a7eR5n2Jh6 X-Received: by 2002:adf:ee4f:: with SMTP id w15mr27575553wro.199.1617007973440; Mon, 29 Mar 2021 01:52:53 -0700 (PDT) X-Google-Smtp-Source: ABdhPJy14ggZeyOKD8MLg/euq/YSevg+wh8nYXfPT6TAJxwjaDv2zhx7W6453bwTkfCmynppamOy1g== X-Received: by 2002:adf:ee4f:: with SMTP id w15mr27575538wro.199.1617007973184; Mon, 29 Mar 2021 01:52:53 -0700 (PDT) Received: from vitty.brq.redhat.com (g-server-2.ign.cz. [91.219.240.2]) by smtp.gmail.com with ESMTPSA id s9sm26301602wmh.31.2021.03.29.01.52.52 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 29 Mar 2021 01:52:52 -0700 (PDT) From: Vitaly Kuznetsov To: Paolo Bonzini , kvm@vger.kernel.org Cc: Sean Christopherson , Wanpeng Li , Jim Mattson , Wei Huang , Joerg Roedel , linux-kernel@vger.kernel.org Subject: Re: [PATCH] KVM: x86/vPMU: Forbid writing to MSR_F15H_PERF MSRs when guest doesn't have X86_FEATURE_PERFCTR_CORE In-Reply-To: References: <20210323084515.1346540-1-vkuznets@redhat.com> Date: Mon, 29 Mar 2021 10:52:51 +0200 Message-ID: <874kgubau4.fsf@vitty.brq.redhat.com> MIME-Version: 1.0 Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org Paolo Bonzini writes: > On 23/03/21 09:45, Vitaly Kuznetsov wrote: >> MSR_F15H_PERF_CTL0-5, MSR_F15H_PERF_CTR0-5 MSRs are only available when >> X86_FEATURE_PERFCTR_CORE CPUID bit was exposed to the guest. KVM, however, >> allows these MSRs unconditionally because kvm_pmu_is_valid_msr() -> >> amd_msr_idx_to_pmc() check always passes and because kvm_pmu_set_msr() -> >> amd_pmu_set_msr() doesn't fail. >> >> In case of a counter (CTRn), no big harm is done as we only increase >> internal PMC's value but in case of an eventsel (CTLn), we go deep into >> perf internals with a non-existing counter. >> >> Note, kvm_get_msr_common() just returns '0' when these MSRs don't exist >> and this also seems to contradict architectural behavior which is #GP >> (I did check one old Opteron host) but changing this status quo is a bit >> scarier. > > Hmm, since these do have a cpuid bit it may not be that scary. Well, if you're not scared I can send a patch) -- Vitaly