[PATCH v2] iommu/arm-smmu-v3: Limit queue allocation retry boundary to PAGE_SIZE

[PATCH v2] iommu/arm-smmu-v3: Limit queue allocation retry boundary to PAGE_SIZE

[Leo Jiang]

In arm_smmu_init_one_queue(), the driver attempts to allocate the largest
supported queue and retries by halving the size on failure. Currently,
the retry logic allows the allocation to fall below PAGE_SIZE if the
PAGE_SIZE attempt fails.

While dmam_alloc_coherent() can theoretically return allocations smaller
than a page in certain configurations, it is preferable to limit the
retry boundary to PAGE_SIZE for SMMUv3 queues to align with the
original design intent.

This patch ensures the retry loop terminates when qsz reaches PAGE_SIZE,
per the feedback from the maintainer.

Signed-off-by: Leo Jiang <leo.jiang1224@foxmail.com>
---
v2:
- Use real name "Leo Jiang".
- Remove code comments as suggested by Will.
- Limit the queue allocation retry boundary to PAGE_SIZE

 drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
index e8d7dbe495f0..4a0b15b1d4d2 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
@@ -4418,7 +4418,7 @@ int arm_smmu_init_one_queue(struct arm_smmu_device *smmu,
 		qsz = ((1 << q->llq.max_n_shift) * dwords) << 3;
 		q->base = dmam_alloc_coherent(smmu->dev, qsz, &q->base_dma,
 					      GFP_KERNEL);
-		if (q->base || qsz < PAGE_SIZE)
+		if (q->base || qsz <= PAGE_SIZE)
 			break;
 
 		q->llq.max_n_shift--;
-- 
2.34.1

[PATCH v2] iommu/arm-smmu-v3: Limit queue allocation retry boundary to PAGE_SIZE

[Leo Jiang]

Stop retrying queue allocation when qsz reaches PAGE_SIZE.

Signed-off-by: Leo Jiang <leo.jiang1224@foxmail.com>
---
Changes in v2:
- Use real name "Leo Jiang".
- Remove code comments as suggested by Will.
- Limit the queue allocation retry boundary to PAGE_SIZE, per the feedback from the maintainer.
- Link to v1: https://lore.kernel.org/linux-iommu/tencent_F6E384A40D990A279B460A0CDE1927FDF509@qq.com
---
 drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
index e8d7dbe495f0..4a0b15b1d4d2 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
@@ -4418,7 +4418,7 @@ int arm_smmu_init_one_queue(struct arm_smmu_device *smmu,
 		qsz = ((1 << q->llq.max_n_shift) * dwords) << 3;
 		q->base = dmam_alloc_coherent(smmu->dev, qsz, &q->base_dma,
 					      GFP_KERNEL);
-		if (q->base || qsz < PAGE_SIZE)
+		if (q->base || qsz <= PAGE_SIZE)
 			break;
 
 		q->llq.max_n_shift--;
-- 
2.34.1