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PowerPC book3s 4K mostly has the same definition on both, except
pXd_huge() constantly returns 0 for hash MMUs.  As Michael Ellerman
pointed out [1], it is safe to check _PAGE_PTE on hash MMUs, as the bit
will never be set so it will keep returning false.

As a reference, __p[mu]d_mkhuge() will trigger a BUG_ON trying to create
such huge mappings for 4K hash MMUs.  Meanwhile, the major powerpc hugetlb
pgtable walker __find_linux_pte() already used pXd_leaf() to check leaf
hugetlb mappings.

The goal should be that we will have one API pXd_leaf() to detect all
kinds of huge mappings (hugepd is still special in this case, though). 
AFAICT we need to use the pXd_leaf() impl (rather than pXd_huge()'s) to
make sure ie.  THPs on hash MMU will also return true.

This helps to simplify a follow up patch to drop pXd_huge() treewide.

NOTE: *_leaf() definition need to be moved before the inclusion of
asm/book3s/64/pgtable-4k.h, which defines pXd_huge() with it.

[1] https://lore.kernel.org/r/87v85zo6w7.fsf@mail.lhotse

Link: https://lkml.kernel.org/r/20240318200404.448346-10-peterx@redhat.com

Signed-off-by: Peter Xu <peterx@redhat.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@kernel.org>
Cc: "Naveen N. Rao" <naveen.n.rao@linux.ibm.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Andreas Larsson <andreas@gaisler.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Bjorn Andersson <andersson@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Fabio Estevam <festevam@denx.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Konrad Dybcio <konrad.dybcio@linaro.org>
Cc: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Cc: Lucas Stach <l.stach@pengutronix.de>
Cc: Mark Salter <msalter@redhat.com>
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Cc: Mike Rapoport (IBM) <rppt@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Naoya Horiguchi <nao.horiguchi@gmail.com>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Shawn Guo <shawnguo@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>