From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paolo Bonzini Subject: Re: [PATCH] KVM: VMX: Preserve host CR4.MCE value while in guest mode. Date: Fri, 17 Apr 2015 12:16:18 +0200 Message-ID: <5530DD72.7010801@redhat.com> References: <1429210685-19510-1-git-send-email-serebrin@google.com> <20150417051007.GA3080@kernel> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Cc: kvm@vger.kernel.org, stable@vger.kernel.org, luto@amacapital.net, jankiszka@siemens.com To: Wanpeng Li , Ben Serebrin Return-path: Received: from mx1.redhat.com ([209.132.183.28]:45902 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750744AbbDQKQe (ORCPT ); Fri, 17 Apr 2015 06:16:34 -0400 In-Reply-To: <20150417051007.GA3080@kernel> Sender: kvm-owner@vger.kernel.org List-ID: On 17/04/2015 07:10, Wanpeng Li wrote: >> > >> >Before the change, if guest CR4.MCE==0, then the machine check is >> >escalated to Catastrophic Error (CATERR) and the machine dies. > Could you point out which section of SDM describes that the machine check > is escalated to a CATERR if CR4.MCE==0? It's under the description of "Interrupt 18--Machine-Check Exception (#MC)": The machine-check mechanism is enabled by setting the MCE flag in control register CR4. [...] If the machine-check mechanism is not enabled (the MCE flag in control register CR4 is clear), a machine-check exception causes the processor to enter the shutdown state. This of course also applies whenever the non-root mode CR4 (*not* the shadow CR4 in the VMCS!) has the MCE flag cleared. Paolo