From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paolo Bonzini Subject: Re: [PATCH 1/6] target-arm: kvm: save/restore mp state Date: Tue, 03 Mar 2015 18:10:12 +0100 Message-ID: <54F5EAF4.2000206@redhat.com> References: <1424880159-29348-1-git-send-email-alex.bennee@linaro.org> <1424880159-29348-2-git-send-email-alex.bennee@linaro.org> <8761ai73j1.fsf@linaro.org> <54F595C0.5060004@redhat.com> <87zj7u59hd.fsf@linaro.org> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: kvm-devel , Marc Zyngier , QEMU Developers , "kvmarm@lists.cs.columbia.edu" , arm-mail-list To: =?UTF-8?B?QWxleCBCZW5uw6ll?= , Peter Maydell Return-path: Received: from mail-wg0-f50.google.com ([74.125.82.50]:41572 "EHLO mail-wg0-f50.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757035AbbCCRKS (ORCPT ); Tue, 3 Mar 2015 12:10:18 -0500 Received: by wghl18 with SMTP id l18so41367255wgh.8 for ; Tue, 03 Mar 2015 09:10:16 -0800 (PST) In-Reply-To: <87zj7u59hd.fsf@linaro.org> Sender: kvm-owner@vger.kernel.org List-ID: On 03/03/2015 17:30, Alex Benn=C3=A9e wrote: >> > >>> >> Right now this is not migrated on ARM if I remember correctly, = but >>> >> perhaps you'll want to add it in the future. >> > >> > ...which is why we don't need to migrate this: it just means >> > that migration during WFI causes an unnecessary-wakeup, which >> > is architecturally fine. > What happens when you boot a SMP system but only ever power up one of= the > CPUs? You can't just randomly start the second CPU if it's in the > powered off state, who knows what it would do? The second CPU would not be in the WFI state, which is what Peter is talking about. I agree that this state should be saved/restored. I'm just saying that HALTED is not the right constant to use. Paolo