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iommu/amd: Use try_cmpxchg64() in v2_alloc_pte()

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Use try_cmpxchg64() instead of cmpxchg64 (*ptr, old, new) != old in
v2_alloc_pte().  cmpxchg returns success in ZF flag, so this change
saves a compare after cmpxchg (and related move instruction
in front of cmpxchg).

This is the same improvement as implemented for alloc_pte() in:

  commit 0d10fe7591 ("iommu/amd: Use try_cmpxchg64 in alloc_pte and free_clear_pte")

Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Cc: Joerg Roedel <joro@8bytes.org>
Cc: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
Cc: Will Deacon <will@kernel.org>
Cc: Robin Murphy <robin.murphy@arm.com>
Reviewed-by: Vasant Hegde <vasant.hegde@amd.com>
Link: https://lore.kernel.org/r/20240522082729.971123-1-ubizjak@gmail.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>
This commit is contained in:
Uros Bizjak
2024-05-22 10:26:47 +02:00
committed by Joerg Roedel
parent 83a7eefedc
commit 9a448e4531
1 changed files with 1 additions and 1 deletions
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2
drivers/iommu/amd/io_pgtable_v2.c
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@@ -158,7 +158,7 @@ static u64 *v2_alloc_pte(int nid, u64 *pgd, unsigned long iova,
__npte = set_pgtable_attr(page);
/* pte could have been changed somewhere. */
if (cmpxchg64(pte, __pte, __npte) != __pte)
if (!try_cmpxchg64(pte, &__pte, __npte))
iommu_free_page(page);
else if (IOMMU_PTE_PRESENT(__pte))
*updated = true;