On Thu, Jun 10, 2021 at 7:52 AM Horia Geantă <horia.geanta@xxxxxxx> wrote:
>
> Documentation/core-api/dma-api.rst explicitly allows for partial syncs:
> Synchronise a single contiguous or scatter/gather mapping for the CPU
> and device. With the sync_sg API, all the parameters must be the same
> as those passed into the single mapping API. With the sync_single API,
> you can use dma_handle and size parameters that aren't identical to
> those passed into the single mapping API to do a partial sync.
>
> AFAICS commit 16fc3cef33a0 ("swiotlb: don't modify orig_addr in swiotlb_tbl_sync_single")
> is breaking this functionality.
How about a patch like the attached? Does that fix things for you.
Christoph? Comments - that commit removed the offset calculation
entirely, because the old
(unsigned long)tlb_addr & (IO_TLB_SIZE - 1)
was wrong, but instead of removing it, I think it should have just
fixed it to be
(tlb_addr - mem->start) & (IO_TLB_SIZE - 1);
instead. That way the slot offset always matches the slot index calculation.
I also made it then take the offset into account for the alloc_size checks.
Does this UNTESTED patch perhaps do the right thing?
Linus
kernel/dma/swiotlb.c | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
index 8ca7d505d61c..f63d15e94d35 100644
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c
@@ -342,6 +342,7 @@ static void swiotlb_bounce(struct device *dev, phys_addr_t tlb_addr, size_t size
{
struct io_tlb_mem *mem = io_tlb_default_mem;
int index = (tlb_addr - mem->start) >> IO_TLB_SHIFT;
+ unsigned long offset = (tlb_addr - mem->start) & (IO_TLB_SIZE - 1);
phys_addr_t orig_addr = mem->slots[index].orig_addr;
size_t alloc_size = mem->slots[index].alloc_size;
unsigned long pfn = PFN_DOWN(orig_addr);
@@ -350,6 +351,14 @@ static void swiotlb_bounce(struct device *dev, phys_addr_t tlb_addr, size_t size
if (orig_addr == INVALID_PHYS_ADDR)
return;
+ if (offset > alloc_size) {
+ dev_WARN_ONCE(dev, 1,
+ "Buffer overflow detected. Offset: %lu. Mapping size: %zu.\n",
+ offset, size);
+ return;
+ }
+ alloc_size -= offset;
+ orig_addr += offset;
if (size > alloc_size) {
dev_WARN_ONCE(dev, 1,
"Buffer overflow detected. Allocation size: %zu. Mapping size: %zu.\n",
