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[84.255.245.182]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3502b79bc0asm33964495f8f.1.2024.05.22.01.27.31 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 22 May 2024 01:27:31 -0700 (PDT) From: Uros Bizjak To: iommu@lists.linux.dev, linux-kernel@vger.kernel.org Cc: Uros Bizjak , Joerg Roedel , Suravee Suthikulpanit , Will Deacon , Robin Murphy Subject: [PATCH 1/3] iommu/amd: Use try_cmpxchg64() in v2_alloc_pte() Date: Wed, 22 May 2024 10:26:47 +0200 Message-ID: <20240522082729.971123-1-ubizjak@gmail.com> X-Mailer: git-send-email 2.45.1 Precedence: bulk X-Mailing-List: iommu@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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 Cc: Joerg Roedel Cc: Suravee Suthikulpanit Cc: Will Deacon Cc: Robin Murphy --- 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