2021-05-10 09:12:20

by Chanho Park

[permalink] [raw]
Subject: [PATCH v2] swiotlb: manipulate orig_addr when tlb_addr has offset

From: Bumyong Lee <[email protected]>

in case of driver wants to sync part of ranges with offset,
swiotlb_tbl_sync_single() copies from orig_addr base to tlb_addr with
offset it makes data mismatch

it removed from
- "swiotlb: don't modify orig_addr in swiotlb_tbl_sync_single",
but it have to be recovered due to below case.

1. Get dma_addr_t from dma_map_single()
dma_addr_t tlb_addr = dma_map_single(dev, vaddr, vsize, DMA_TO_DEVICE);

|<---------------vsize------------->|
+-----------------------------------+
| | original buffer
+-----------------------------------+
vaddr

swiotlb_align_offset
|<----->|<---------------vsize------------->|
+-------+-----------------------------------+
| | | swiotlb buffer
+-------+-----------------------------------+
tlb_addr

2. Do something
3. Sync dma_addr_t through dma_sync_single_for_device(..)
dma_sync_single_for_device(dev, tlb_addr + offset, size, DMA_TO_DEVICE);

Error case.
copy data to original buffer.
but it is from base addr in original buffer

|<----->|<- offset ->|<- size ->|
+-------+-----------------------------------+
| | |##########| | swiotlb buffer
+-------+-----------------------------------+
tlb_addr

swiotlb_align_offset
|<----->|<- offset ->|<- size ->|
+-------+-----------------------------------+
| | |##########| | swiotlb buffer
+-------+-----------------------------------+
tlb_addr

|<- size ->|
+-----------------------------------+
|##########| | original buffer
+-----------------------------------+
vaddr

FIX. copy data to original buffer.
but it is from base addr in original buffer

swiotlb_align_offset
|<----->|<- offset ->|<- size ->|
+-------+-----------------------------------+
| | |##########| | swiotlb buffer
+-------+-----------------------------------+
tlb_addr

|<- offset ->|<- size ->|
+-----------------------------------+
| |##########| | original buffer
+-----------------------------------+
vaddr

Fixes: 16fc3cef33a0 ("swiotlb: don't modify orig_addr in swiotlb_tbl_sync_single")
Signed-off-by: Bumyong Lee <[email protected]>
Signed-off-by: Chanho Park <[email protected]>
---
Changes since v1:
- Move swiotlb_align_offset to avoid forward declaration
- Make tlb_offset calculation as single assignment

kernel/dma/swiotlb.c | 23 +++++++++++++++--------
1 file changed, 15 insertions(+), 8 deletions(-)

diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
index 8ca7d505d61c..e50df8d8f87e 100644
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c
@@ -334,6 +334,14 @@ void __init swiotlb_exit(void)
io_tlb_default_mem = NULL;
}

+/*
+ * Return the offset into a iotlb slot required to keep the device happy.
+ */
+static unsigned int swiotlb_align_offset(struct device *dev, u64 addr)
+{
+ return addr & dma_get_min_align_mask(dev) & (IO_TLB_SIZE - 1);
+}
+
/*
* Bounce: copy the swiotlb buffer from or back to the original dma location
*/
@@ -346,10 +354,17 @@ static void swiotlb_bounce(struct device *dev, phys_addr_t tlb_addr, size_t size
size_t alloc_size = mem->slots[index].alloc_size;
unsigned long pfn = PFN_DOWN(orig_addr);
unsigned char *vaddr = phys_to_virt(tlb_addr);
+ unsigned int tlb_offset;

if (orig_addr == INVALID_PHYS_ADDR)
return;

+ tlb_offset = (tlb_addr & (IO_TLB_SIZE - 1)) -
+ swiotlb_align_offset(dev, orig_addr);
+
+ orig_addr += tlb_offset;
+ alloc_size -= tlb_offset;
+
if (size > alloc_size) {
dev_WARN_ONCE(dev, 1,
"Buffer overflow detected. Allocation size: %zu. Mapping size: %zu.\n",
@@ -390,14 +405,6 @@ static void swiotlb_bounce(struct device *dev, phys_addr_t tlb_addr, size_t size

#define slot_addr(start, idx) ((start) + ((idx) << IO_TLB_SHIFT))

-/*
- * Return the offset into a iotlb slot required to keep the device happy.
- */
-static unsigned int swiotlb_align_offset(struct device *dev, u64 addr)
-{
- return addr & dma_get_min_align_mask(dev) & (IO_TLB_SIZE - 1);
-}
-
/*
* Carefully handle integer overflow which can occur when boundary_mask == ~0UL.
*/
--
2.31.1