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Date: Tue, 30 Jul 2013 10:59:13 -0600
From: Stephen Warren <swarren@wwwdotorg.org>
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Subject: Re: [PATCH] ARM: kexec: offline non panic CPUs on Kdump panic
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To: Vijay Kilari <vijay.kilari@gmail.com>
Cc: "linux@arm.linux.org.uk" <linux@arm.linux.org.uk>, "Prasun.Kapoor@caviumnetworks.com" <Prasun.Kapoor@caviumnetworks.com>, Will Deacon <will.deacon@arm.com>, Vijaya Kumar K <Vijaya.Kumar@caviumnetworks.com>, "kexec@lists.infradead.org" <kexec@lists.infradead.org>, "linux-arm-kernel@lists.infradead.org" <linux-arm-kernel@lists.infradead.org>

On 07/30/2013 04:37 AM, Vijay Kilari wrote:
> On Fri, Jul 26, 2013 at 10:38 PM, Stephen Warren <swarren@wwwdotorg.org> wrote:
...
>> Does a kernel that's used as the crash kernel guarantee:
>>
>> * Never to re-use the memory that was used by the previous kernel, so
>> that the spin loop code/data won't be corrupted, ever, no matter how
>> long the crash recovery kernel runs.
>>
>> * Not use SMP, so there's never a need to re-activate the non-boot CPUs,
>> which might not work if they aren't truly disabled but rather just
>> running a pin loop?
> 
> From cat /proc/iomem, normal kernel is executed from (0x80xxxxxx) with crash
> kernel reserved 64M@0xa0000000
> 
> 80000000-bfffffff : System RAM
>   80008000-805aeddf : Kernel code
>   805e2000-8063e427 : Kernel data
>   a0000000-a3ffffff : Crash kernel
> 
> crash kernel is loaded to reserved memory location and is executed from there.
> I could confirm this from /proc/iomem when crash kernel is running
> 
> a0000000-a3efffff : System RAM
>   a0008000-a05aeddf : Kernel code
>   a05e2000-a063e427 : Kernel data

OK, but in the crash dump kernel, is 80008000..8063e427 reserved as
well, which would guarantee that the spin loop being executed by the
non-crash CPUs won't be corrupted?

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