From mboxrd@z Thu Jan 1 00:00:00 1970 From: Radim =?utf-8?B?S3LEjW3DocWZ?= Subject: Re: [PATCH] KVM: x86: Add three MSRs to the list of ignored MSRs Date: Thu, 14 Apr 2016 18:29:08 +0200 Message-ID: <20160414162907.GB3350@potion.brq.redhat.com> References: <1460626109-24343-1-git-send-email-shuai.ruan@linux.intel.com> <20160414133332.GA3350@potion.brq.redhat.com> <570FAC6F.10704@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: Shuai Ruan , kvm@vger.kernel.org, allen.m.kay@intel.com To: Paolo Bonzini Return-path: Received: from mx1.redhat.com ([209.132.183.28]:57358 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932370AbcDNQ3M (ORCPT ); Thu, 14 Apr 2016 12:29:12 -0400 Content-Disposition: inline In-Reply-To: <570FAC6F.10704@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: 2016-04-14 16:42+0200, Paolo Bonzini: > On 14/04/2016 15:33, Radim Kr=C4=8Dm=C3=A1=C5=99 wrote: >> The main bug in KVM is that it allows the guest to think that it run= s on >> CPU that isn't emulated: any CPU that has MSR_PLATFORM_INFO shouldn= 't >> be exposed in KVM. >=20 > That's all of them. f/m/s values and the model name are a useful > debugging tool. Considering that MSR_PLATFORM_INFO is hardly ever us= ed, > it doesn't seem to be a great compromise. I don't see that as a compromise. igd would fail even if we fixed the host side, so we'll have problems regardless of what we do. We have a bug, because certain v/f/m/s implies some features (MSRs, constant_tsc, ...) and those aren't emulated. I do agree that we don't want to fix the bug, either by whitelisting an= d emulating features that makes little sense in virt or by forcing guests to adopt new v/f/m/s (the latter option is more reasonable), because rare occurences of the bug take *much* less work to fix on the guest side. (The only part I'm concerned about is that we don't have a good excuse for some guest errors ...)