Messages in this thread Patch in this message | | | From | Uros Bizjak <> | Subject | [PATCH 1/3] iommu/amd: Use try_cmpxchg64() in v2_alloc_pte() | Date | Wed, 22 May 2024 10:26:47 +0200 |
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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 0d10fe759117 ("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> --- drivers/iommu/amd/io_pgtable_v2.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/iommu/amd/io_pgtable_v2.c b/drivers/iommu/amd/io_pgtable_v2.c index 78ac37c5ccc1..664e91c88748 100644 --- a/drivers/iommu/amd/io_pgtable_v2.c +++ b/drivers/iommu/amd/io_pgtable_v2.c @@ -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; -- 2.45.1
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