From 9a448e453151ec4e4b98a914b463539e790dd198 Mon Sep 17 00:00:00 2001
From: Uros Bizjak <ubizjak@gmail.com>
Date: Wed, 22 May 2024 10:26:47 +0200
Subject: [PATCH] iommu/amd: Use try_cmpxchg64() in v2_alloc_pte()
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>
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>
---
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 78ac37c5ccc1e..664e91c88748e 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;
--
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