Commit 5c555f1f authored by Uros Bizjak's avatar Uros Bizjak Committed by Joerg Roedel
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iommu/vt-d: Use try_cmpxchg64() in intel_pasid_get_entry() 



Use try_cmpxchg64() instead of cmpxchg64 (*ptr, old, new) != old in
intel_pasid_get_entry().  cmpxchg returns success in ZF flag, so
this change saves a compare after cmpxchg (and related move
instruction in front of cmpxchg).

Signed-off-by: default avatarUros 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: default avatarLu Baolu <baolu.lu@linux.intel.com>
Link: https://lore.kernel.org/r/20240522082729.971123-2-ubizjak@gmail.com


Signed-off-by: default avatarJoerg Roedel <jroedel@suse.de>
parent 83a7eefe

drivers/iommu/intel/pasid.c

+5 −2
Original line number Diff line number Diff line
@@ -146,6 +146,8 @@ static struct pasid_entry *intel_pasid_get_entry(struct device *dev, u32 pasid) 
retry:

	entries = get_pasid_table_from_pde(&dir[dir_index]);

	if (!entries) {

		u64 tmp;



		entries = iommu_alloc_page_node(info->iommu->node, GFP_ATOMIC);

		if (!entries)

			return NULL;
@@ -156,7 +158,8 @@ static struct pasid_entry *intel_pasid_get_entry(struct device *dev, u32 pasid) 
		 * clear. However, this entry might be populated by others

		 * while we are preparing it. Use theirs with a retry.

		 */

		if (cmpxchg64(&dir[dir_index].val, 0ULL,

		tmp = 0ULL;

		if (!try_cmpxchg64(&dir[dir_index].val, &tmp,

				   (u64)virt_to_phys(entries) | PASID_PTE_PRESENT)) {

			iommu_free_page(entries);

			goto retry;