From: Will Deacon <will.deacon@arm.com>
To: Stephen Warren <swarren@wwwdotorg.org>
Cc: "linux-tegra@vger.kernel.org" <linux-tegra@vger.kernel.org>,
Stephen Warren <swarren@nvidia.com>,
"kexec@lists.infradead.org" <kexec@lists.infradead.org>,
Eric Biederman <ebiederm@xmission.com>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH] kexec: disable non-boot CPUs
Date: Thu, 20 Dec 2012 10:49:45 +0000 [thread overview]
Message-ID: <20121220104945.GC16887@mudshark.cambridge.arm.com> (raw)
In-Reply-To: <1355960681-32015-1-git-send-email-swarren@wwwdotorg.org>
Hi Stephen,
On Wed, Dec 19, 2012 at 11:44:41PM +0000, Stephen Warren wrote:
> From: Stephen Warren <swarren@nvidia.com>
>
> Both the regular reboot and shutdown paths do this. It seems reasonable
> for kexec to work the same way.
>
> On the Tegra ARM SoC at least, this change allows kexec to work with SMP
> enabled. ARM's machine_shutdown() simply puts all CPUs into a loop. If
> the code of that loop is over-written, the CPUs may crash, and cause the
> kexec'd kernel not to be able to initialize them. In practice, this
> causes the kexec'd kernel to hang and/or crash. The intended way to
> solve this is for ARM machines to provide a cpu_kill SMP operation to
> e.g. power down the CPUs, or place them in reset. However, at least on
> Tegra, the implementation of that function would simply be duplicating
> the hotplug code that already exists, so it seems simpler to just call
> disable_nonboot_cpus() for the kexec path, just like reboot/shutdown.
If you do manage to get this merged, please can you follow up with a patch
to remove the smp_kill_cpus bits from arch/arm/kernel/smp.c please? It only
exists as a hook to do exactly this and currently nobody is using it afaict.
Cheers,
Will
_______________________________________________
kexec mailing list
kexec@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/kexec
WARNING: multiple messages have this Message-ID (diff)
From: Will Deacon <will.deacon-5wv7dgnIgG8@public.gmane.org>
To: Stephen Warren <swarren-3lzwWm7+Weoh9ZMKESR00Q@public.gmane.org>
Cc: "linux-tegra-u79uwXL29TY76Z2rM5mHXA@public.gmane.org"
<linux-tegra-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
Stephen Warren <swarren-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>,
"kexec-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org"
<kexec-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org>,
Eric Biederman <ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org>,
"linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org"
<linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org>
Subject: Re: [PATCH] kexec: disable non-boot CPUs
Date: Thu, 20 Dec 2012 10:49:45 +0000 [thread overview]
Message-ID: <20121220104945.GC16887@mudshark.cambridge.arm.com> (raw)
In-Reply-To: <1355960681-32015-1-git-send-email-swarren-3lzwWm7+Weoh9ZMKESR00Q@public.gmane.org>
Hi Stephen,
On Wed, Dec 19, 2012 at 11:44:41PM +0000, Stephen Warren wrote:
> From: Stephen Warren <swarren-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>
>
> Both the regular reboot and shutdown paths do this. It seems reasonable
> for kexec to work the same way.
>
> On the Tegra ARM SoC at least, this change allows kexec to work with SMP
> enabled. ARM's machine_shutdown() simply puts all CPUs into a loop. If
> the code of that loop is over-written, the CPUs may crash, and cause the
> kexec'd kernel not to be able to initialize them. In practice, this
> causes the kexec'd kernel to hang and/or crash. The intended way to
> solve this is for ARM machines to provide a cpu_kill SMP operation to
> e.g. power down the CPUs, or place them in reset. However, at least on
> Tegra, the implementation of that function would simply be duplicating
> the hotplug code that already exists, so it seems simpler to just call
> disable_nonboot_cpus() for the kexec path, just like reboot/shutdown.
If you do manage to get this merged, please can you follow up with a patch
to remove the smp_kill_cpus bits from arch/arm/kernel/smp.c please? It only
exists as a hook to do exactly this and currently nobody is using it afaict.
Cheers,
Will
WARNING: multiple messages have this Message-ID (diff)
From: will.deacon@arm.com (Will Deacon)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH] kexec: disable non-boot CPUs
Date: Thu, 20 Dec 2012 10:49:45 +0000 [thread overview]
Message-ID: <20121220104945.GC16887@mudshark.cambridge.arm.com> (raw)
In-Reply-To: <1355960681-32015-1-git-send-email-swarren@wwwdotorg.org>
Hi Stephen,
On Wed, Dec 19, 2012 at 11:44:41PM +0000, Stephen Warren wrote:
> From: Stephen Warren <swarren@nvidia.com>
>
> Both the regular reboot and shutdown paths do this. It seems reasonable
> for kexec to work the same way.
>
> On the Tegra ARM SoC at least, this change allows kexec to work with SMP
> enabled. ARM's machine_shutdown() simply puts all CPUs into a loop. If
> the code of that loop is over-written, the CPUs may crash, and cause the
> kexec'd kernel not to be able to initialize them. In practice, this
> causes the kexec'd kernel to hang and/or crash. The intended way to
> solve this is for ARM machines to provide a cpu_kill SMP operation to
> e.g. power down the CPUs, or place them in reset. However, at least on
> Tegra, the implementation of that function would simply be duplicating
> the hotplug code that already exists, so it seems simpler to just call
> disable_nonboot_cpus() for the kexec path, just like reboot/shutdown.
If you do manage to get this merged, please can you follow up with a patch
to remove the smp_kill_cpus bits from arch/arm/kernel/smp.c please? It only
exists as a hook to do exactly this and currently nobody is using it afaict.
Cheers,
Will
next prev parent reply other threads:[~2012-12-20 10:49 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-12-19 23:44 [PATCH] kexec: disable non-boot CPUs Stephen Warren
2012-12-19 23:44 ` Stephen Warren
2012-12-19 23:44 ` Stephen Warren
2012-12-19 23:55 ` Eric W. Biederman
2012-12-19 23:55 ` Eric W. Biederman
2012-12-19 23:55 ` Eric W. Biederman
2012-12-20 10:49 ` Will Deacon [this message]
2012-12-20 10:49 ` Will Deacon
2012-12-20 10:49 ` Will Deacon
2012-12-20 17:21 ` Stephen Warren
2012-12-20 17:21 ` Stephen Warren
2012-12-20 17:21 ` Stephen Warren
2012-12-20 17:36 ` Will Deacon
2012-12-20 17:36 ` Will Deacon
2012-12-20 17:36 ` Will Deacon
2012-12-20 17:59 ` Stephen Warren
2012-12-20 17:59 ` Stephen Warren
2012-12-20 17:59 ` Stephen Warren
2012-12-20 20:15 ` Stephen Warren
2012-12-20 20:15 ` Stephen Warren
2012-12-20 20:15 ` Stephen Warren
2012-12-23 11:06 ` Will Deacon
2012-12-23 11:06 ` Will Deacon
2012-12-23 11:06 ` Will Deacon
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