From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752417AbeBZKGq (ORCPT ); Mon, 26 Feb 2018 05:06:46 -0500 Received: from mail-oi0-f65.google.com ([209.85.218.65]:34725 "EHLO mail-oi0-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751609AbeBZKGn (ORCPT ); Mon, 26 Feb 2018 05:06:43 -0500 X-Google-Smtp-Source: AG47ELvwu5VyRVyth3FZgx6yzSz7RhVoK2Uvf/3+PQpQisiEt3RbKc8FpYxHoRd0/HuMlnJeHf0lXvYsaRn3NmmzCGs= MIME-Version: 1.0 In-Reply-To: <20180226094148.GA15539@pd.tnic> References: <1519629838-4898-1-git-send-email-wanpengli@tencent.com> <20180226094148.GA15539@pd.tnic> From: Wanpeng Li Date: Mon, 26 Feb 2018 18:06:42 +0800 Message-ID: Subject: Re: [PATCH] KVM: X86: Allow userspace to define the microcode version To: Borislav Petkov Cc: LKML , kvm , Paolo Bonzini , =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 2018-02-26 17:41 GMT+08:00 Borislav Petkov : > On Mon, Feb 26, 2018 at 03:23:58PM +0800, Wanpeng Li wrote: >> From: Wanpeng Li >> >> Linux (among the others) has checks to make sure that certain features >> aren't enabled on a certain family/model/stepping if the microcode version >> isn't greater than or equal to a known good version. >> >> By exposing the real microcode version, we're preventing buggy guests that > > Where do we prevent userspace from coming up with some non-sensical > microcode revision? I think it is the host admin(e.g. cloud provider)'s responsibility to set an expected microcode revision. In addition, the non-sensical value which is written by the guest will not reflect to guest-visible microcode revision and just be ignored in this implementation. Regards, Wanpeng Li