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 Return-path: In-Reply-To: <87zj7u59hd.fsf@linaro.org> Sender: kvm-owner@vger.kernel.org To: =?UTF-8?B?QWxleCBCZW5uw6ll?= , Peter Maydell Cc: kvm-devel , Marc Zyngier , QEMU Developers , "kvmarm@lists.cs.columbia.edu" , arm-mail-list List-Id: kvmarm@lists.cs.columbia.edu 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 From mboxrd@z Thu Jan 1 00:00:00 1970 From: pbonzini@redhat.com (Paolo Bonzini) Date: Tue, 03 Mar 2015 18:10:12 +0100 Subject: [PATCH 1/6] target-arm: kvm: save/restore mp state In-Reply-To: <87zj7u59hd.fsf@linaro.org> 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> Message-ID: <54F5EAF4.2000206@redhat.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 03/03/2015 17:30, Alex Benn?e 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 From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:53367) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YSqKs-0006U1-SE for qemu-devel@nongnu.org; Tue, 03 Mar 2015 12:10:23 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1YSqKn-0007xA-9H for qemu-devel@nongnu.org; Tue, 03 Mar 2015 12:10:22 -0500 Received: from mail-wi0-x235.google.com ([2a00:1450:400c:c05::235]:38751) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YSqKn-0007x2-31 for qemu-devel@nongnu.org; Tue, 03 Mar 2015 12:10:17 -0500 Received: by wiwh11 with SMTP id h11so24507128wiw.3 for ; Tue, 03 Mar 2015 09:10:16 -0800 (PST) Sender: Paolo Bonzini Message-ID: <54F5EAF4.2000206@redhat.com> Date: Tue, 03 Mar 2015 18:10:12 +0100 From: Paolo Bonzini MIME-Version: 1.0 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> In-Reply-To: <87zj7u59hd.fsf@linaro.org> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Subject: Re: [Qemu-devel] [PATCH 1/6] target-arm: kvm: save/restore mp state List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: =?UTF-8?B?QWxleCBCZW5uw6ll?= , Peter Maydell Cc: Marc Zyngier , arm-mail-list , QEMU Developers , kvm-devel , "kvmarm@lists.cs.columbia.edu" On 03/03/2015 17:30, Alex Bennée 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