From: Tianyu Lan <Tianyu.Lan@xxxxxxxxxxxxx>
swiotlb_find_slots() skips slots according to io tlb aligned mask
calculated from min aligned mask and original physical address
offset. This affects max mapping size. The mapping size can't
achieve the IO_TLB_SEGSIZE * IO_TLB_SIZE when original offset is
non-zero. This will cause system boot up failure in Hyper-V
Isolation VM where swiotlb force is enabled. Scsi layer use return
value of dma_max_mapping_size() to set max segment size and it
finally calls swiotlb_max_mapping_size(). Hyper-V storage driver
sets min align mask to 4k - 1. Scsi layer may pass 256k length of
request buffer with 0~4k offset and Hyper-V storage driver can't
get swiotlb bounce buffer via DMA API. Swiotlb_find_slots() can't
find 256k length bounce buffer with offset. Make swiotlb_max_mapping
_size() take min align mask into account.
Signed-off-by: Tianyu Lan <Tianyu.Lan@xxxxxxxxxxxxx>
---
kernel/dma/swiotlb.c | 13 ++++++++++++-
1 file changed, 12 insertions(+), 1 deletion(-)
diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
index 73a41cec9e38..0d6684ca7eab 100644
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c
@@ -743,7 +743,18 @@ dma_addr_t swiotlb_map(struct device *dev, phys_addr_t paddr, size_t size,
size_t swiotlb_max_mapping_size(struct device *dev)
{
- return ((size_t)IO_TLB_SIZE) * IO_TLB_SEGSIZE;
+ int min_align_mask = dma_get_min_align_mask(dev);
+ int min_align = 0;
+
+ /*
+ * swiotlb_find_slots() skips slots according to
+ * min align mask. This affects max mapping size.
+ * Take it into acount here.
+ */
+ if (min_align_mask)
+ min_align = roundup(min_align_mask, IO_TLB_SIZE);
+
+ return ((size_t)IO_TLB_SIZE) * IO_TLB_SEGSIZE - min_align;
}
bool is_swiotlb_active(struct device *dev)
--
2.25.1
