From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S944596AbdDTLJn (ORCPT ); Thu, 20 Apr 2017 07:09:43 -0400 Received: from mx1.redhat.com ([209.132.183.28]:43910 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S942050AbdDTLJi (ORCPT ); Thu, 20 Apr 2017 07:09:38 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com 6218D75755 Authentication-Results: ext-mx01.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx01.extmail.prod.ext.phx2.redhat.com; spf=pass smtp.mailfrom=david@redhat.com DKIM-Filter: OpenDKIM Filter v2.11.0 mx1.redhat.com 6218D75755 Subject: Re: [PATCH v5] x86: call smp vmxoff in smp stop To: Paolo Bonzini , linux-kernel@vger.kernel.org, kvm@vger.kernel.org References: <20170419161839.30550-1-pbonzini@redhat.com> Cc: mingo@kernel.org, x86@kernel.org, Tiantian Feng , Xishi Qiu From: David Hildenbrand Organization: Red Hat GmbH Message-ID: Date: Thu, 20 Apr 2017 13:09:36 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.8.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.25]); Thu, 20 Apr 2017 11:09:38 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 20.04.2017 12:13, Paolo Bonzini wrote: > > > On 20/04/2017 12:01, David Hildenbrand wrote: >> On 19.04.2017 18:18, Paolo Bonzini wrote: >>> From: Tiantian Feng >>> >>> A CPU in VMX root mode will ignore INIT signals and fail to bring >>> up the APs after reboot. Therefore, on a panic we disable VMX on all >>> CPUs before rebooting or triggering kdump. >>> >>> Do this when halting the machine as well, in case a firmware-level reboot >>> does not perform a cold reset for all processors. Without doing this, >>> rebooting the host may hang. >> >> Guess this make sense, just wonder if something like that is actually >> expected to work? Not doing a cold reset feels like leaving a lot of >> stuff in an uninitialized state. Shouldn't that specific firmware then >> care about performing any necessary resets? > > Yes, but it cannot do them if it cannot even perform the initial warm > reset ("INIT"). > > It's probably rare, after all the original introduction of > cpu_emergency_vmxoff is as old as 2008 and it took nine years for > someone to think of making this extra change. Right, so this is really a special case. I think this is just fine. The same problem with !vmm_exclusive as with other callers of cpu_emergency_vmxoff(), but that should be solved as soon as vmm_exclusive is dropped. Reviewed-by: David Hildenbrand -- Thanks, David