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 1E88BC4332F for ; Wed, 9 Nov 2022 14:52:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229863AbiKIOwD (ORCPT ); Wed, 9 Nov 2022 09:52:03 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58872 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231684AbiKIOwB (ORCPT ); Wed, 9 Nov 2022 09:52:01 -0500 Received: from mail-pj1-x102b.google.com (mail-pj1-x102b.google.com [IPv6:2607:f8b0:4864:20::102b]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1C6F5DCB for ; Wed, 9 Nov 2022 06:52:00 -0800 (PST) Received: by mail-pj1-x102b.google.com with SMTP id o7so16938882pjj.1 for ; Wed, 09 Nov 2022 06:52:00 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=XeOFALjP4//bjPWLGTjPjIDysDczrY32pqpS/JBJ2aM=; b=dzc2j21Z19okNpdO/OG3vUOhmVC//w/sykljjJTVJPG9Bwyi9Dg3GqsAX8V6j4q58k Jzwfq2I5a8tktAdnuywWGW1D71R0jq1CQ33O6h0k8v1xyqOyXQ3DCygTa//OdE/Qczuj rqofOhdMAXa8nSHmLrpMM58HWgun+/+buQiLWVWtldZVCJmTabOe+ZnRO17Saux+xPep B4WHFfFjQKAdQxVfx2SUIi5wzcNpl4jFEoY0GGSkYLz4YTh7MTk5rP/0URlZpNEz28pR zW5z0xsNpW7DZheVbJBSS8hEvlzJnAa3Mii13K7mIT3MN/AGpE7PwpvmRlICa+umCy8E gsaw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=XeOFALjP4//bjPWLGTjPjIDysDczrY32pqpS/JBJ2aM=; b=Fo6rJrfvN5eBZBWlRpFh5VQRJvRBNhxoj0UerXVD0IbbLjTs70yYIl44Lj8Vk27VXS E+c8jlfqtdpspzdyMxXbOokLNw5KFbmCyna6E4LlrO7FNVF2WSVMYdVoq/ySrIf44dtg pYhv1mK0fTcB2DT+8VIazoKkYB/wfJ1/vuknaHIW4ERNAtekWO11mlVeIIi1FK5COQLJ vRA6WIF/lEnZV7hD/GsE7pw1RXy5soclRCXF18E1zRkRn9h85jSEnE7gRS0Q8K1e6ebr MDXQ8LOapRaTbjlowsFuzDhLeriFhq+EP7qg9PXtgyxSeD2Yv5v99tEaJKjSGsgEn9QA 7FcA== X-Gm-Message-State: ACrzQf1tKf1Y4zLeg7jkVjQdd/hS3aAPvnVUTB/G3FkwZNVFbo5l05m0 EBMMjCgks9bUtc0vgHkI34mYPw== X-Google-Smtp-Source: AMsMyM7cS/NQlLGyLM98aZixQixRLTspiMLHh8S33ld8nKp+9Cn7QtIiI2O2s0Q+Rpwuhtg5XFXL5g== X-Received: by 2002:a17:902:b68b:b0:186:aee0:53ec with SMTP id c11-20020a170902b68b00b00186aee053ecmr62375926pls.90.1668005519533; Wed, 09 Nov 2022 06:51:59 -0800 (PST) Received: from google.com (7.104.168.34.bc.googleusercontent.com. [34.168.104.7]) by smtp.gmail.com with ESMTPSA id a2-20020a170902710200b00176b3d7db49sm9224863pll.0.2022.11.09.06.51.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 09 Nov 2022 06:51:58 -0800 (PST) Date: Wed, 9 Nov 2022 14:51:55 +0000 From: Sean Christopherson To: Like Xu Cc: Paolo Bonzini , kvm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 2/3] KVM: x86/svm/pmu: Add AMD PerfMonV2 support Message-ID: References: <20220919093453.71737-1-likexu@tencent.com> <20220919093453.71737-3-likexu@tencent.com> <107f4040-e4cd-82df-01bc-f0d6a22be053@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <107f4040-e4cd-82df-01bc-f0d6a22be053@gmail.com> Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Wed, Nov 09, 2022, Like Xu wrote: > On 28/10/2022 6:47 am, Sean Christopherson wrote: > > What happens if userspace sets X86_FEATURE_PERFCTR_CORE when its not supported? > > E.g. will KVM be coerced into taking a #GP on a non-existent counter? > > I'm getting a bit tired of this generic issue, what does KVM need to do when > the KVM user space sets a capability that KVM doesn't support (like cpuid). > Should it change the guest cpuid audibly or silently ? Should it report an > error when the guest uses this unsupported capability at run time, or should > it just let the KVM report an error when user space setting the cpuid ? KVM should do nothing unless the bogus CPUID can be used to trigger unexpected and/or unwanted behavior in the kernel, which is why I asked if KVM might end up taking a #GP.