From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andi Kleen Subject: Re: [PATCH] [2/2] KVM: Add VT-x machine check support Date: Thu, 4 Jun 2009 15:01:07 +0200 Message-ID: <20090604130107.GA1065@one.firstfloor.org> References: <20090604112.650907584@firstfloor.org> <20090604111205.C47C31D0282@basil.firstfloor.org> <4A27B481.5020003@redhat.com> <20090604125123.GY1065@one.firstfloor.org> <4A27C2BF.3090108@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Andi Kleen , ying.huang@intel.com, kvm@vger.kernel.org, linux-kernel@vger.kernel.org To: Avi Kivity Return-path: Received: from one.firstfloor.org ([213.235.205.2]:60986 "EHLO one.firstfloor.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758304AbZFDMxy (ORCPT ); Thu, 4 Jun 2009 08:53:54 -0400 Content-Disposition: inline In-Reply-To: <4A27C2BF.3090108@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On Thu, Jun 04, 2009 at 03:49:03PM +0300, Avi Kivity wrote: > Andi Kleen wrote: > >>This assumption is incorrect. This code is executed after preemption > >>has been enabled, and we may have even slept before reaching it. > >> > > > >The only thing that counts here is the context before the machine > >check event. If there was a vmexit we know it was in guest context. > > > >The only requirement we have is that we're running still on the same > >CPU. I assume that's true, otherwise the vmcb accesses wouldn't work? > > > > It's not true, we're in preemptible context and may have even slept. > > vmcs access work because we have a preempt notifier called when we are > scheduled in, and will execute vmclear/vmptrld as necessary. Look at > kvm_preempt_ops in virt/kvm_main.c. I see. So we need to move that check earlier. Do you have a preference where it should be? -Andi -- ak@linux.intel.com -- Speaking for myself only.