From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752922AbeBZLy5 (ORCPT ); Mon, 26 Feb 2018 06:54:57 -0500 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:42088 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752322AbeBZLyz (ORCPT ); Mon, 26 Feb 2018 06:54:55 -0500 Subject: Re: [PATCH] KVM: X86: Allow userspace to define the microcode version To: Borislav Petkov , Wanpeng Li Cc: LKML , kvm , =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= References: <1519629838-4898-1-git-send-email-wanpengli@tencent.com> <20180226094148.GA15539@pd.tnic> <20180226104921.GA4377@pd.tnic> <20180226111630.GB4377@pd.tnic> <20180226113000.GC4377@pd.tnic> <20180226114409.GD4377@pd.tnic> From: Paolo Bonzini Message-ID: <46cecef2-b0fb-b0c2-bbf3-983328d52763@redhat.com> Date: Mon, 26 Feb 2018 12:54:52 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.6.0 MIME-Version: 1.0 In-Reply-To: <20180226114409.GD4377@pd.tnic> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 26/02/2018 12:44, Borislav Petkov wrote: >> The guest write is ignored as the original kvm implementation before the patch. > > That will never work because there's no virtualized microcode loader. > Which will be a dumb idea anyway. > > Goes to show that dealing with microcode revisions for a guest is the > wrong approach. I don't understand how one thing follows from the other. How are writes to 0x8B related to having a virtualized microcode loaded (which is a concept that actually makes no sense at all)? > So that's basically what I'm saying - fix apic_check_deadline_errata() > to check whether the kernel runs as a guest. It has already been fixed for a few months, and fixing it is indeed the right thing to do independent of this patch. Paolo