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

Vijay Kilari
2013-08-01T13:49:13Z

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