Re: [PATCH v2 RESEND] mm/sparsemem: pfn_to_page is not valid yet on SPARSEMEM

[Mike Rapoport]

On Wed, Feb 19, 2020 at 08:37:25AM -0800, Dan Williams wrote:
> On Wed, Feb 19, 2020 at 12:57 AM Mike Rapoport <rppt@xxxxxxxxxxxxx> wrote:
> >
> > On Tue, Feb 18, 2020 at 07:25:15PM -0800, Dan Williams wrote:
> > > On Tue, Feb 18, 2020 at 7:05 PM Baoquan He <bhe@xxxxxxxxxx> wrote:
> > > >
> > > > From: Wei Yang <richardw.yang@xxxxxxxxxxxxxxx>
> > > >
> > > > When we use SPARSEMEM instead of SPARSEMEM_VMEMMAP, pfn_to_page()
> > > > doesn't work before sparse_init_one_section() is called. This leads to a
> > > > crash when hotplug memory:
> > >
> > > I'd also add:
> > >
> > > "On x86 the impact is limited to x86_32 builds, or x86_64
> > > configurations that override the default setting for
> > > SPARSEMEM_VMEMMAP".
> >
> > Do we also want to check how it affects, say, arm64, ia64 and ppc? ;-)
> 
> Sure, I just did not take the time to look up their respective default
> stances on SPARSEMEM_VMEMMAP. For a distro looking to backport this
> commit I think it's helpful for them to understand if they are exposed
> or not.

Looks like only i386_defconfig does not enable SPARSEMEM_VMEMMAP. All the
rest may have it disabled only with manual override.

-- 
Sincerely yours,
Mike.