Re: [PATCH 1/2] vmcore: allow alternate dump capturing methods to export vmcore without is_kdump_kernel()

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On 05/09/23 8:00 am, Baoquan He wrote:
On 09/04/23 at 08:04pm, Hari Bathini wrote:
Hi Baoquan,

Thanks for the review...

On 03/09/23 9:06 am, Baoquan He wrote:
Hi Hari,

On 09/02/23 at 12:34am, Hari Bathini wrote:
Currently, is_kdump_kernel() returns true when elfcorehdr_addr is set.
While elfcorehdr_addr is set for kexec based kernel dump mechanism,
alternate dump capturing methods like fadump [1] also set it to export
the vmcore. is_kdump_kernel() is used to restrict resources in crash
dump capture kernel but such restrictions may not be desirable for
fadump. Allow is_kdump_kernel() to be defined differently for such
scenarios. With this, is_kdump_kernel() could be false while vmcore
is usable. So, introduce is_crashdump_kernel() to return true when
elfcorehdr_addr is set and use it for vmcore related checks.

I got what is done in these two patches, but didn't get why they need be
done. vmcore_unusable()/is_vmcore_usable() are only unitilized in ia64.
Why do you care if it's is_crashdump_kernel() or is_kdump_kernel()?
If you want to override the generic is_kdump_kernel() with powerpc's own
is_kdump_kernel(), your below change is enough to allow you to do that.
I can't see why is_crashdump_kernel() is needed. Could you explain that
specifically?

You mean to just remove is_kdump_kernel() check in is_vmcore_usable() &
vmcore_unusable() functions? Replaced generic is_crashdump_kernel()
function instead, that returns true for any dump capturing method,
irrespective of whether is_kdump_kernel() returns true or false.
For fadump case, is_kdump_kernel() will return false after patch 2/2.

OK, I could understand what you want to achieve. You want to make
is_kdump_kernel() only return true for kdump, while is_vmcore_usable()
returns true for both kdump and fadump.

IIUC, can we change as below? It could make code clearer and more
straightforward. I don't think adding another is_crashdump_kernel()
is a good idea, that would be a torture for non-powerpc people reading
code when they need differentiate between kdump and crashdump.


Sure, Baoquan.
Posted v2 based on your suggestion.

Thanks
Hari

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