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iommu/vt-d: Use try_cmpxchg64() in intel_pasid_get_entry()

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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: 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: Lu Baolu <baolu.lu@linux.intel.com>
Link: https://lore.kernel.org/r/20240522082729.971123-2-ubizjak@gmail.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>
This commit is contained in:
Uros Bizjak 2024-05-22 10:26:48 +02:00 committed by Joerg Roedel
parent 83a7eefedc
commit 5c555f1f1c
1 changed files with 5 additions and 2 deletions
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7
drivers/iommu/intel/pasid.c
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@ -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;
@ -156,8 +158,9 @@ retry:
* 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,
(u64)virt_to_phys(entries) | PASID_PTE_PRESENT)) {
tmp = 0ULL;
if (!try_cmpxchg64(&dir[dir_index].val, &tmp,
(u64)virt_to_phys(entries) | PASID_PTE_PRESENT)) {
iommu_free_page(entries);
goto retry;
}