From 9e7ee0f045395dc8aa55fbdc164c062484f4c88d Mon Sep 17 00:00:00 2001 From: Uros Bizjak Date: Wed, 24 Apr 2024 15:16:28 +0800 Subject: iommu/vt-d: Use try_cmpxchg64{,_local}() in iommu.c Replace this pattern in iommu.c: cmpxchg64{,_local}(*ptr, 0, new) != 0 ... with the simpler and faster: !try_cmpxchg64{,_local}(*ptr, &tmp, new) The x86 CMPXCHG instruction returns success in the ZF flag, so this change saves a compare after the CMPXCHG. No functional change intended. Signed-off-by: Uros Bizjak Cc: David Woodhouse Cc: Lu Baolu Cc: Joerg Roedel Cc: Will Deacon Cc: Robin Murphy Reviewed-by: Jason Gunthorpe Link: https://lore.kernel.org/r/20240414162454.49584-1-ubizjak@gmail.com Signed-off-by: Lu Baolu Signed-off-by: Joerg Roedel --- drivers/iommu/intel/iommu.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) (limited to 'drivers/iommu/intel') diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c index a7ecd90303dc..4a2afe89b464 100644 --- a/drivers/iommu/intel/iommu.c +++ b/drivers/iommu/intel/iommu.c @@ -865,7 +865,7 @@ static struct dma_pte *pfn_to_dma_pte(struct dmar_domain *domain, break; if (!dma_pte_present(pte)) { - uint64_t pteval; + uint64_t pteval, tmp; tmp_page = alloc_pgtable_page(domain->nid, gfp); @@ -877,7 +877,8 @@ static struct dma_pte *pfn_to_dma_pte(struct dmar_domain *domain, if (domain->use_first_level) pteval |= DMA_FL_PTE_XD | DMA_FL_PTE_US | DMA_FL_PTE_ACCESS; - if (cmpxchg64(&pte->val, 0ULL, pteval)) + tmp = 0ULL; + if (!try_cmpxchg64(&pte->val, &tmp, pteval)) /* Someone else set it while we were thinking; use theirs. */ free_pgtable_page(tmp_page); else @@ -2128,8 +2129,8 @@ __domain_mapping(struct dmar_domain *domain, unsigned long iov_pfn, /* We don't need lock here, nobody else * touches the iova range */ - tmp = cmpxchg64_local(&pte->val, 0ULL, pteval); - if (tmp) { + tmp = 0ULL; + if (!try_cmpxchg64_local(&pte->val, &tmp, pteval)) { static int dumps = 5; pr_crit("ERROR: DMA PTE for vPFN 0x%lx already set (to %llx not %llx)\n", iov_pfn, tmp, (unsigned long long)pteval); -- cgit v1.2.3