On 05/06/2020 01:13 PM, Will Deacon wrote:

On Wed, May 06, 2020 at 11:42:12AM +0530, Anshuman Khandual wrote:

quoted

Platform specific huge_ptep_get() is required only when fetching the huge
PTE involves more than just dereferencing the page table pointer. This is
not the case on arm64 platform. Hence huge_ptep_pte() can be dropped along
with it's __HAVE_ARCH_HUGE_PTEP_GET subscription.

Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-mm@kvack.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Anshuman Khandual <redacted>
---
 arch/arm64/include/asm/hugetlb.h | 6 ------
 1 file changed, 6 deletions(-)

diff --git a/arch/arm64/include/asm/hugetlb.h b/arch/arm64/include/asm/hugetlb.h
index 2eb6c234d594..b88878ddc88b 100644
--- a/arch/arm64/include/asm/hugetlb.h
+++ b/arch/arm64/include/asm/hugetlb.h

@@ -17,12 +17,6 @@
 extern bool arch_hugetlb_migration_supported(struct hstate *h);
 #endif
 
-#define __HAVE_ARCH_HUGE_PTEP_GET
-static inline pte_t huge_ptep_get(pte_t *ptep)
-{
-	return READ_ONCE(*ptep);
-}

Hmm, I'm nervous about dropping the READ_ONCE() here. We added them after
running into page-table issues with THP [1] and it's really important to
use them consistently to avoid hitting that again.

If the generic code used READ_ONCE(), I'd be happy to switch to it.

Sure, will add READ_ONCE() in the generic huge_ptep_get(). AFAICS it should
not cause any problem for other platforms (but let me know otherwise).

Will

[1] https://lore.kernel.org/lkml/1506527369-19535-1-git-send-email-will.deacon@arm.com/ (local)

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