Re: [RFC V3 PATCH] arm64: mm: swap: save and restore mte tags for large folios

[Yang Shi]

On Wed, Nov 15, 2023 at 12:49 PM Barry Song <21cnbao@xxxxxxxxx> wrote:
>
> On Wed, Nov 15, 2023 at 11:16 PM David Hildenbrand <david@xxxxxxxxxx> wrote:
> >
> > On 14.11.23 02:43, Barry Song wrote:
> > > This patch makes MTE tags saving and restoring support large folios,
> > > then we don't need to split them into base pages for swapping out
> > > on ARM64 SoCs with MTE.
> > >
> > > arch_prepare_to_swap() should take folio rather than page as parameter
> > > because we support THP swap-out as a whole.
> > >
> > > Meanwhile, arch_swap_restore() should use page parameter rather than
> > > folio as swap-in always works at the granularity of base pages right
> > > now.
> >
> > ... but then we always have order-0 folios and can pass a folio, or what
> > am I missing?
>
> Hi David,
> you missed the discussion here:
>
> https://lore.kernel.org/lkml/CAGsJ_4yXjex8txgEGt7+WMKp4uDQTn-fR06ijv4Ac68MkhjMDw@xxxxxxxxxxxxxx/
> https://lore.kernel.org/lkml/CAGsJ_4xmBAcApyK8NgVQeX_Znp5e8D4fbbhGguOkNzmh1Veocg@xxxxxxxxxxxxxx/
>
> >
> > >
> > > arch_thp_swp_supported() is dropped since ARM64 MTE was the only one
> > > who needed it.
> >
> > Can we do that separately?
>
> i think it is ok.

IMHO keeping it in this patch makes more sense. IIRC removing
arch_thp_swp_supported() is just because this patch made swapping
large folio with MTE more efficiently.

>
> >
> > --
> > Cheers,
> >
> > David / dhildenb
> >
>
> Thanks
> Barry