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=-2.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 E72D9C2D0B1 for ; Thu, 6 Feb 2020 14:21:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B8FB221741 for ; Thu, 6 Feb 2020 14:21:45 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="D4Qoe6ox" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727976AbgBFOVp (ORCPT ); Thu, 6 Feb 2020 09:21:45 -0500 Received: from us-smtp-delivery-1.mimecast.com ([207.211.31.120]:29592 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727415AbgBFOVo (ORCPT ); Thu, 6 Feb 2020 09:21:44 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1580998904; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=p1NHUo5yQAkCKpQ/gtz43IUIp+O0qG9I4nh1OcLn2g4=; b=D4Qoe6oxGmPFY38tXH0Bzx90zfQ3LGwEX8ttJBEA+ti61Tuh9bdUivGmsRvO/S8dOpziGL RNP1SjorefO0HF7Wd5NnXeHt7NtdPIijXTvm5rfSFbFRrXgtGJLhtPu7QAzhroeMlDGLNi fhHTxxCIOhEsw6VNoqrpiKYQ62G0r3A= Received: from mail-wr1-f70.google.com (mail-wr1-f70.google.com [209.85.221.70]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-297-UeeXuSS7PLmol8P47ewmDw-1; Thu, 06 Feb 2020 09:21:41 -0500 X-MC-Unique: UeeXuSS7PLmol8P47ewmDw-1 Received: by mail-wr1-f70.google.com with SMTP id x15so3440964wrl.15 for ; Thu, 06 Feb 2020 06:21:41 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=p1NHUo5yQAkCKpQ/gtz43IUIp+O0qG9I4nh1OcLn2g4=; b=H9eA7t4KvQiHvsKRMNRW7G6wL3/PPGFJ8CCNID6sskH189UEwqBfFtXgzTRO5nGysZ ojYRKQj2zwuMRhANAGMOafzlCeAi4yrcLSKC+5oraBalznFqaF7+ay8XZI96z3ybr/Vc GUkM1YD7vZBotAhtHhd9xTwVfVJYgq17xAjwLatwfdfPtKjDQXkzNPij7QkTQ5DQDsI5 meOg70/2NgjBQNg/bnjKsl7SpURKrqCoVvDeS2sbTJAMDHutBfrpY4zPsV6/e0wFOcnz PeKTPZkfUdqM7SZByihLL+5SyFMa74YF3cPM35SJDFwkMnfC1Jdh3hTTdX4KK87FWbi4 VSnQ== X-Gm-Message-State: APjAAAWJFVSHayqG87yaIY7Vak1aTv3i3sk6le30Wk2kD3zyuhxshNQp GpXjl+Ltc80Df2xDh4gTRLL/HbGzftbob/Oyuv+hss8V0WVsr0XjNZY6Gt5hEXSpphQ7xK0zPVG oYUGZ/7eTgDpi/qILo9ncW6yt X-Received: by 2002:a5d:4cc9:: with SMTP id c9mr4057196wrt.70.1580998900571; Thu, 06 Feb 2020 06:21:40 -0800 (PST) X-Google-Smtp-Source: APXvYqwmKqbasnwi3c9xJwfBnQhwneGX9h1gBvBaMW2W0NIbjIO6EvQ3zKfNpz+yqNd1aMOaSsJviw== X-Received: by 2002:a5d:4cc9:: with SMTP id c9mr4057175wrt.70.1580998900322; Thu, 06 Feb 2020 06:21:40 -0800 (PST) Received: from [10.201.49.5] (nat-pool-mxp-u.redhat.com. [149.6.153.187]) by smtp.gmail.com with ESMTPSA id w7sm3804381wmi.9.2020.02.06.06.21.38 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 06 Feb 2020 06:21:39 -0800 (PST) Subject: Re: [PATCH] KVM: SVM: relax conditions for allowing MSR_IA32_SPEC_CTRL accesses To: Vitaly Kuznetsov Cc: dgilbert@redhat.com, jmattson@google.com, linux-kernel@vger.kernel.org, kvm@vger.kernel.org References: <1580915628-42930-1-git-send-email-pbonzini@redhat.com> <87v9ojg5r1.fsf@vitty.brq.redhat.com> From: Paolo Bonzini Message-ID: <1d7f50a2-3c3f-dd18-a635-aa4eaa757fa3@redhat.com> Date: Thu, 6 Feb 2020 15:21:37 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.1.1 MIME-Version: 1.0 In-Reply-To: <87v9ojg5r1.fsf@vitty.brq.redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 06/02/20 15:17, Vitaly Kuznetsov wrote: > Reviewed-by: Vitaly Kuznetsov > > but out of pure curiosity, why do we need these checks? > > At least for the 'set' case right below them we have: > > if (data & ~kvm_spec_ctrl_valid_bits(vcpu)) > return 1; > > so if guest will try using unsupported features it will #GP. So > basically, these checks will only fire when reading/writing '0' and all > features are missing, right? Do we care? Probably not... I just wanted the smallest possible change in semantics for this patch, and the rest can be done equally on Intel and AMD. Paolo