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Subject[PATCH] iommu/amd: Fix alloc_irq_index() increment
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On an is_allocated() interrupt index, we ALIGN() the current index and
then increment it via the for loop, guaranteeing that it is no longer
aligned for alignments >1. We instead need to align the next index,
to guarantee forward progress, moving the increment-only to the case
where the index was found to be unallocated.

Fixes: 37946d95fc1a ('iommu/amd: Add align parameter to alloc_irq_index()')
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
---
drivers/iommu/amd_iommu.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/iommu/amd_iommu.c b/drivers/iommu/amd_iommu.c
index 9dc7facfd2e5..3c1a29104f0e 100644
--- a/drivers/iommu/amd_iommu.c
+++ b/drivers/iommu/amd_iommu.c
@@ -3682,13 +3682,12 @@ static int alloc_irq_index(u16 devid, int count, bool align)

/* Scan table for free entries */
for (index = ALIGN(table->min_index, alignment), c = 0;
- index < MAX_IRQS_PER_TABLE;
- index++) {
+ index < MAX_IRQS_PER_TABLE;) {
if (!iommu->irte_ops->is_allocated(table, index)) {
c += 1;
} else {
c = 0;
- index = ALIGN(index, alignment);
+ index = ALIGN(index + 1, alignment);
continue;
}

@@ -3699,6 +3698,8 @@ static int alloc_irq_index(u16 devid, int count, bool align)
index -= count - 1;
goto out;
}
+
+ index++;
}

index = -ENOSPC;
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