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

[Hari Bathini]

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