linux-kernel - Re: [PATCH] powerpc: on crash, kexec'ed kernel needs all CPUs are online

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Message-ID: <1445047433.24309.40.camel@kernel.crashing.org>
Date:	Sat, 17 Oct 2015 07:33:53 +0530
From:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:	Laurent Vivier <lvivier@...hat.com>,
	David Gibson <dgibson@...hat.com>
Cc:	Paul Mackerras <paulus@...ba.org>,
	Michael Ellerman <mpe@...erman.id.au>,
	linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
	thuth@...hat.com
Subject: Re: [PATCH] powerpc: on crash, kexec'ed kernel needs all CPUs are
 online

On Fri, 2015-10-16 at 09:57 +0200, Laurent Vivier wrote:
> For me the problem is: as these CPUs are offline, I guess the core has
> been switched to 1 thread per core, so the CPUs (1 to 7 for core 0)
> don't exist anymore, how can we return them to OPAL ?

Another option is to make the new kernel kick_cpu fallback, if it knows
it's coming as a crashdump, to sending IPIs.

We would need some sane way to catch the guys coming it at 0x100 and
route the to secondary start.

Cheers,
Ben.

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