From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1031397AbdDTKNO (ORCPT ); Thu, 20 Apr 2017 06:13:14 -0400 Received: from mx1.redhat.com ([209.132.183.28]:60552 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1031220AbdDTKNM (ORCPT ); Thu, 20 Apr 2017 06:13:12 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com 51AA166CB0 Authentication-Results: ext-mx09.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx09.extmail.prod.ext.phx2.redhat.com; spf=pass smtp.mailfrom=pbonzini@redhat.com DKIM-Filter: OpenDKIM Filter v2.11.0 mx1.redhat.com 51AA166CB0 Subject: Re: [PATCH v5] x86: call smp vmxoff in smp stop To: David Hildenbrand , 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: Paolo Bonzini Message-ID: Date: Thu, 20 Apr 2017 12:13:01 +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 [10.5.110.38]); Thu, 20 Apr 2017 10:13:11 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. Paolo