[PATCH v16 07/45] arm64: mm: Handle Granule Protection Faults (GPFs)

[Will Deacon]

On Wed, Aug 12, 2026 at 02:51:29PM +0100, Catalin Marinas wrote:
> On Wed, Aug 12, 2026 at 06:12:09PM +0530, Pavan Kondeti wrote:
> > There is a valid case for fixup_exception() to be needed here in GPF
> > handling.
> > 
> > -000 |load_unaligned_zeropad(inline)
> > -000 |hash_name(inline)
> > -000 |link_path_walk()
> > -001 |path_lookupat()
> > -002 |filename_lookup()
> > -003 |vfs_statx()
> > -004 |vfs_fstatat()
> > 
> > We observed this in Android running Gunyah when the page is mapped in
> > EL1 but unmapped at EL2. path_lookupat() can actually handle this
> > via fixup_exeption() when a word load crosses the page boundary.
> > However, Gunyah injects a Synchronous External Abort and we have
> > a downstream patch [1] that adds fixup_exception() in do_sea(). pKVM
> > injects [2] such faults back to EL1 and fixup_exception() is taken care.
> 
> Ah, good point, completely forgot about load_unaligned_zeropad(). Since
> we don't unmap the linear map for delegated pages, we'll need the
> fixup_exception(). And I guess warning in this case is not desirable
> either. We could limit it to EX_TYPE_KACCESS_ERR_ZERO and
> EX_TYPE_LOAD_UNALIGNED_ZEROPAD, though not sure it's worth it.

Alternatively, I think the series to unmap guest memory from the linear
map would solve that for gmem:

https://lore.kernel.org/all/20260410151746.61150-1-kalyazin@amazon.com/

but I can't tell whether that's still being actively pursued.

Will