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iommu/vt-d: Use try_cmpxchg64{,_local}() in iommu.c

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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 <ubizjak@gmail.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Lu Baolu <baolu.lu@linux.intel.com>
Cc: Joerg Roedel <joro@8bytes.org>
Cc: Will Deacon <will@kernel.org>
Cc: Robin Murphy <robin.murphy@arm.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/20240414162454.49584-1-ubizjak@gmail.com
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>
This commit is contained in:
Uros Bizjak 2024-04-24 15:16:28 +08:00 committed by Joerg Roedel
parent a770ccd91d
commit 9e7ee0f045
1 changed files with 5 additions and 4 deletions
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9
drivers/iommu/intel/iommu.c
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@ -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);