Steven Price's on July 1, 2019 7:57 pm:

On 01/07/2019 07:40, Nicholas Piggin wrote:

quoted

walk_page_range() is going to be allowed to walk page tables other than
those of user space. For this it needs to know when it has reached a
'leaf' entry in the page tables. This information will be provided by the
p?d_large() functions/macros.

For arm64, we already have p?d_sect() macros which we can reuse for
p?d_large().

pud_sect() is defined as a dummy function when CONFIG_PGTABLE_LEVELS < 3
or CONFIG_ARM64_64K_PAGES is defined. However when the kernel is
configured this way then architecturally it isn't allowed to have a
large page that this level, and any code using these page walking macros
is implicitly relying on the page size/number of levels being the same as
the kernel. So it is safe to reuse this for p?d_large() as it is an
architectural restriction.

Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <redacted>
Signed-off-by: Steven Price <steven.price@arm.com>

Hi Nicolas,

This appears to my patch which I originally posted as part of converting
x86/arm64 to use a generic page walk code[1].

Hey, yeah it is, I'd intended to mark you as the author but must have
forgot to change it in git.

I'm not sure that this
patch makes much sense on its own, in particular it was working up to
having a generic macro[2] which means the _large() macros could be used
across all architectures.

It goes with this series which makes _large macros usable for archs
that define HUGE_VMAP. I posted the same thing earlier and Anshuman
noted you'd done it too so I deferred to yours (I thought it would
go via arm64 tree and that this would just allow Andrew to easily
reconcile the merge).

If your series is not going upstream this time then the changelog
probably doesn't make so much sense, so I could just send my version
to the arm64 tree.

Thanks,
Nick