Re: [PATCH v12 7/7] x86/crash: Add x86 crash hotplug support

[Eric DeVolder]

On 10/11/22 23:55, Sourabh Jain wrote:
> > > > > > If kmap_local_page() works for all archs, then I'm happy to drop these
> > > > > > arch_ variants and use it directly.
> > > > >
> > > > > Yes, pls do.
> > > >
> > > > I'll check with Sourabh to see if PPC can work with kmap_local_page().
> > > I think kmap_local_page do support on  PowerPC. But can you explain why we need this
> > > function here, aren't the reserve memory already available to use?
> >
> > On x86, attempts to access the elfcorehdr without mapping it did not work (resulted
> > in a fault).
> >
> > Let me know if using kmap_local_page() in place of __va() in arch_map_crash_pages().
> > If it does, then I can eliminate arch_un/map_crash_pages() and use kmap_local_page()
> > directly.
> Hello Eric,
>
> Atleast on ppc64 we have direct mapping available and hence just by doing page shift
> on physical address (__va) we can get valid virtual address on powerpc. In short we don't
> have to generate mapping again to access reserved region.
>
> Regardless let's go with kdump_local_page API, it is supported on powerpc.
>
> Thanks,
> Sourabh Jain

Ok, I will go that route.
Thanks!
eric