Re: [PATCH] ARM: kexec: offline non panic CPUs on Kdump panic

Vijay Kilari
2013-08-12T12:18:38Z

On Thu, Aug 1, 2013 at 9:55 PM, Stephen Warren <swarren@wwwdotorg.org> wrote:
> On 08/01/2013 07:49 AM, Vijay Kilari wrote:
>> On Wed, Jul 31, 2013 at 10:44 PM, Stephen Warren <swarren@wwwdotorg.org> wrote:
>>> On 07/31/2013 05:37 AM, Vijay Kilari wrote:
>>>> On Tue, Jul 30, 2013 at 10:29 PM, Stephen Warren <swarren@wwwdotorg.org> wrote:
>>>>> 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?
>>>>
>>>> The crash dump kernel runs from reserved memory area (0xa0000000 - 0xa3effffff).
>>>> So it should not corrupt the memory area of original kernel that was running
>>>> at 0x80000000,where other CPU's are in spin loop.
>>>
>>> What about dynamic allocations?
>>
>> IMHO, it is the kdump functionality to ensure that it won't corrupt
>> original kernel's dynamic allocations
>
> OK, if there are explicit measure to assure this already, then there's
> no issue.

Hi Will,

Can you please consider this patch?

Thanks & Regards
Vijay