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swiotlb: fix a braino in the alignment check fix 

The alignment mask in swiotlb_do_find_slots() masks off the high
bits which are not relevant for the alignment, so multiple
requirements are combined with a bitwise OR rather than AND.
In plain English, the stricter the alignment, the more bits must
be set in iotlb_align_mask.

Confusion may arise from the fact that the same variable is also
used to mask off the offset within a swiotlb slot, which is
achieved with a bitwise AND.

Fixes: 0eee5ae102 ("swiotlb: fix slot alignment checks")
Reported-by: Dexuan Cui <decui@microsoft.com>
Link: https://lore.kernel.org/all/CAA42JLa1y9jJ7BgQvXeUYQh-K2mDNHd2BYZ4iZUz33r5zY7oAQ@mail.gmail.com/
Reported-by: Kelsey Steele <kelseysteele@linux.microsoft.com>
Link: https://lore.kernel.org/all/20230405003549.GA21326@linuxonhyperv3.guj3yctzbm1etfxqx2vob5hsef.xx.internal.cloudapp.net/
Signed-off-by: Petr Tesarik <petr.tesarik.ext@huawei.com>
Tested-by: Dexuan Cui <decui@microsoft.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
This commit is contained in:
Petr Tesarik 2023-04-06 16:35:39 +02:00 committed by Christoph Hellwig
parent 0eee5ae102
commit bbb73a103f
1 changed files with 3 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
kernel/dma/swiotlb.c
View File

@ -623,7 +623,7 @@ static int swiotlb_do_find_slots(struct device *dev, int area_index,
phys_to_dma_unencrypted(dev, mem->start) & boundary_mask;
unsigned long max_slots = get_max_slots(boundary_mask);
unsigned int iotlb_align_mask =
dma_get_min_align_mask(dev) & ~(IO_TLB_SIZE - 1);
dma_get_min_align_mask(dev) | alloc_align_mask;
unsigned int nslots = nr_slots(alloc_size), stride;
unsigned int offset = swiotlb_align_offset(dev, orig_addr);
unsigned int index, slots_checked, count = 0, i;
@ -639,8 +639,8 @@ static int swiotlb_do_find_slots(struct device *dev, int area_index,
* allocations.
*/
if (alloc_size >= PAGE_SIZE)
iotlb_align_mask &= PAGE_MASK;
iotlb_align_mask &= alloc_align_mask;
iotlb_align_mask |= ~PAGE_MASK;
iotlb_align_mask &= ~(IO_TLB_SIZE - 1);
/*
* For mappings with an alignment requirement don't bother looping to