Re: [RFC] arm64: mm: update max_pfn after memory hotplug

[Georgi Djakov]

On 9/27/2021 6:51 PM, David Hildenbrand wrote:
> On 24.09.21 00:54, Chris Goldsworthy wrote:
> > From: Sudarshan Rajagopalan <quic_sudaraja@xxxxxxxxxxx>
> >
> > After new memory blocks have been hotplugged, max_pfn and max_low_pfn
> > needs updating to reflect on new PFNs being hot added to system.
> >
> > Signed-off-by: Sudarshan Rajagopalan <quic_sudaraja@xxxxxxxxxxx>
> > Signed-off-by: Chris Goldsworthy <quic_cgoldswo@xxxxxxxxxxx>
> > ---
> >   arch/arm64/mm/mmu.c | 5 +++++
> >   1 file changed, 5 insertions(+)
> >
> > diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
> > index cfd9deb..fd85b51 100644
> > --- a/arch/arm64/mm/mmu.c
> > +++ b/arch/arm64/mm/mmu.c
> > @@ -1499,6 +1499,11 @@ int arch_add_memory(int nid, u64 start, u64 size,
> >       if (ret)
> >           __remove_pgd_mapping(swapper_pg_dir,
> >                        __phys_to_virt(start), size);
> > +    else {
> > +        max_pfn = PFN_UP(start + size);
> > +        max_low_pfn = max_pfn;
> > +    }
> > +
> >       return ret;
>
> Note: didn't verify if updating max_low_pfn is correct here.

My understanding is that max_low_pfn defines the low/high memory
boundary and it should be also updated.

Thanks,
Georgi