From: Paolo Bonzini <pbonzini@redhat.com>
To: "Alex Bennée" <alex.bennee@linaro.org>,
"Peter Maydell" <peter.maydell@linaro.org>
Cc: kvm-devel <kvm@vger.kernel.org>,
Marc Zyngier <marc.zyngier@arm.com>,
QEMU Developers <qemu-devel@nongnu.org>,
"kvmarm@lists.cs.columbia.edu" <kvmarm@lists.cs.columbia.edu>,
arm-mail-list <linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH 1/6] target-arm: kvm: save/restore mp state
Date: Tue, 03 Mar 2015 18:10:12 +0100 [thread overview]
Message-ID: <54F5EAF4.2000206@redhat.com> (raw)
In-Reply-To: <87zj7u59hd.fsf@linaro.org>
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
WARNING: multiple messages have this Message-ID (diff)
From: pbonzini@redhat.com (Paolo Bonzini)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH 1/6] target-arm: kvm: save/restore mp state
Date: Tue, 03 Mar 2015 18:10:12 +0100 [thread overview]
Message-ID: <54F5EAF4.2000206@redhat.com> (raw)
In-Reply-To: <87zj7u59hd.fsf@linaro.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
WARNING: multiple messages have this Message-ID (diff)
From: Paolo Bonzini <pbonzini@redhat.com>
To: "Alex Bennée" <alex.bennee@linaro.org>,
"Peter Maydell" <peter.maydell@linaro.org>
Cc: Marc Zyngier <marc.zyngier@arm.com>,
arm-mail-list <linux-arm-kernel@lists.infradead.org>,
QEMU Developers <qemu-devel@nongnu.org>,
kvm-devel <kvm@vger.kernel.org>,
"kvmarm@lists.cs.columbia.edu" <kvmarm@lists.cs.columbia.edu>
Subject: Re: [Qemu-devel] [PATCH 1/6] target-arm: kvm: save/restore mp state
Date: Tue, 03 Mar 2015 18:10:12 +0100 [thread overview]
Message-ID: <54F5EAF4.2000206@redhat.com> (raw)
In-Reply-To: <87zj7u59hd.fsf@linaro.org>
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
next prev parent reply other threads:[~2015-03-03 17:10 UTC|newest]
Thread overview: 73+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-02-25 16:02 [PATCH 0/6] QEMU ARM64 Migration Fixes Alex Bennée
2015-02-25 16:02 ` [Qemu-devel] " Alex Bennée
2015-02-25 16:02 ` Alex Bennée
2015-02-25 16:02 ` [PATCH 1/6] target-arm: kvm: save/restore mp state Alex Bennée
2015-02-25 16:02 ` [Qemu-devel] " Alex Bennée
2015-02-25 16:02 ` Alex Bennée
2015-02-25 23:36 ` Peter Maydell
2015-02-25 23:36 ` [Qemu-devel] " Peter Maydell
2015-02-25 23:36 ` Peter Maydell
2015-03-03 10:56 ` Alex Bennée
2015-03-03 10:56 ` [Qemu-devel] " Alex Bennée
2015-03-03 10:56 ` Alex Bennée
2015-03-03 11:06 ` Paolo Bonzini
2015-03-03 11:06 ` [Qemu-devel] " Paolo Bonzini
2015-03-03 11:06 ` Paolo Bonzini
2015-03-03 11:51 ` Peter Maydell
2015-03-03 11:51 ` [Qemu-devel] " Peter Maydell
2015-03-03 11:51 ` Peter Maydell
2015-03-03 16:30 ` Alex Bennée
2015-03-03 16:30 ` [Qemu-devel] " Alex Bennée
2015-03-03 16:30 ` Alex Bennée
2015-03-03 17:10 ` Paolo Bonzini [this message]
2015-03-03 17:10 ` [Qemu-devel] " Paolo Bonzini
2015-03-03 17:10 ` Paolo Bonzini
2015-02-26 12:57 ` Paolo Bonzini
2015-02-26 12:57 ` [Qemu-devel] " Paolo Bonzini
2015-02-26 12:57 ` Paolo Bonzini
2015-02-25 16:02 ` [PATCH 2/6] arm_gic_kvm.c: restore config before pending IRQs Alex Bennée
2015-02-25 16:02 ` [Qemu-devel] " Alex Bennée
2015-02-25 16:02 ` Alex Bennée
2015-03-02 22:14 ` Christoffer Dall
2015-03-02 22:14 ` [Qemu-devel] " Christoffer Dall
2015-03-02 22:14 ` Christoffer Dall
2015-02-25 16:02 ` [PATCH 3/6] hw/char/pl011: don't keep setting the IRQ if nothing changed Alex Bennée
2015-02-25 16:02 ` [Qemu-devel] " Alex Bennée
2015-02-25 16:02 ` Alex Bennée
2015-02-25 16:02 ` [PATCH 4/6] target-arm/kvm64.c: sync FP register state Alex Bennée
2015-02-25 16:02 ` [Qemu-devel] " Alex Bennée
2015-02-25 16:02 ` Alex Bennée
2015-02-25 16:02 ` [PATCH 5/6] target-arm/kvm64: fix save/restore of SPSR registers Alex Bennée
2015-02-25 16:02 ` [Qemu-devel] " Alex Bennée
2015-02-25 16:02 ` Alex Bennée
2015-02-25 16:02 ` [PATCH 5/6] target-arm/kvm64: fix save/restore of SPSR regs Alex Bennée
2015-02-25 16:02 ` [Qemu-devel] " Alex Bennée
2015-02-25 16:02 ` Alex Bennée
2015-03-02 17:22 ` Christoffer Dall
2015-03-02 17:22 ` [Qemu-devel] " Christoffer Dall
2015-03-02 17:22 ` Christoffer Dall
2015-03-03 11:28 ` Alex Bennée
2015-03-03 11:28 ` [Qemu-devel] " Alex Bennée
2015-03-03 11:28 ` Alex Bennée
2015-03-09 12:56 ` Christoffer Dall
2015-03-09 12:56 ` [Qemu-devel] " Christoffer Dall
2015-03-09 12:56 ` Christoffer Dall
2015-03-09 13:31 ` Peter Maydell
2015-03-09 13:31 ` [Qemu-devel] " Peter Maydell
2015-03-09 13:31 ` Peter Maydell
2015-03-09 16:25 ` Alex Bennée
2015-03-09 16:25 ` [Qemu-devel] " Alex Bennée
2015-03-09 16:25 ` Alex Bennée
2015-03-09 16:25 ` Alex Bennée
2015-03-09 19:31 ` Christoffer Dall
2015-03-09 19:31 ` [Qemu-devel] " Christoffer Dall
2015-03-09 19:31 ` Christoffer Dall
2015-02-25 16:02 ` [PATCH 6/6] target-arm/cpu.h: document why env->spsr exists Alex Bennée
2015-02-25 16:02 ` [Qemu-devel] " Alex Bennée
2015-02-25 16:02 ` Alex Bennée
2015-03-11 15:39 ` [Qemu-devel] " Greg Bellows
2015-03-11 15:39 ` Greg Bellows
2015-03-11 15:39 ` Greg Bellows
2015-03-11 15:47 ` Peter Maydell
2015-03-11 15:47 ` [Qemu-devel] " Peter Maydell
2015-03-11 15:47 ` Peter Maydell
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