diff options
Diffstat (limited to 'kernel/dma/swiotlb.c')
| -rw-r--r-- | kernel/dma/swiotlb.c | 17 |
1 files changed, 12 insertions, 5 deletions
diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c index 01637677736f..26202274784f 100644 --- a/kernel/dma/swiotlb.c +++ b/kernel/dma/swiotlb.c @@ -678,6 +678,11 @@ static struct io_tlb_pool *swiotlb_alloc_pool(struct device *dev, size_t pool_size; size_t tlb_size; + if (nslabs > SLABS_PER_PAGE << MAX_ORDER) { + nslabs = SLABS_PER_PAGE << MAX_ORDER; + nareas = limit_nareas(nareas, nslabs); + } + pool_size = sizeof(*pool) + array_size(sizeof(*pool->areas), nareas); pool = kzalloc(pool_size, gfp); if (!pool) @@ -1296,11 +1301,13 @@ phys_addr_t swiotlb_tbl_map_single(struct device *dev, phys_addr_t orig_addr, pool->slots[index + i].orig_addr = slot_addr(orig_addr, i); tlb_addr = slot_addr(pool->start, index) + offset; /* - * When dir == DMA_FROM_DEVICE we could omit the copy from the orig - * to the tlb buffer, if we knew for sure the device will - * overwrite the entire current content. But we don't. Thus - * unconditional bounce may prevent leaking swiotlb content (i.e. - * kernel memory) to user-space. + * When the device is writing memory, i.e. dir == DMA_FROM_DEVICE, copy + * the original buffer to the TLB buffer before initiating DMA in order + * to preserve the original's data if the device does a partial write, + * i.e. if the device doesn't overwrite the entire buffer. Preserving + * the original data, even if it's garbage, is necessary to match + * hardware behavior. Use of swiotlb is supposed to be transparent, + * i.e. swiotlb must not corrupt memory by clobbering unwritten bytes. */ swiotlb_bounce(dev, tlb_addr, mapping_size, DMA_TO_DEVICE); return tlb_addr; |