This is a note to let you know that I've just added the patch titled
usb: dwc2: Fix DMA alignment to start at allocated boundary
to my usb git tree which can be found at git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git in the usb-linus branch.
The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.)
The patch will hopefully also be merged in Linus's tree for the next -rc kernel release.
If you have any questions about this process, please let me know.
From 56406e017a883b54b339207b230f85599f4d70ae Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Antti=20Sepp=C3=A4l=C3=A4?= a.seppala@gmail.com Date: Thu, 5 Jul 2018 17:31:53 +0300 Subject: usb: dwc2: Fix DMA alignment to start at allocated boundary MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit
The commit 3bc04e28a030 ("usb: dwc2: host: Get aligned DMA in a more supported way") introduced a common way to align DMA allocations. The code in the commit aligns the struct dma_aligned_buffer but the actual DMA address pointed by data[0] gets aligned to an offset from the allocated boundary by the kmalloc_ptr and the old_xfer_buffer pointers.
This is against the recommendation in Documentation/DMA-API.txt which states:
Therefore, it is recommended that driver writers who don't take special care to determine the cache line size at run time only map virtual regions that begin and end on page boundaries (which are guaranteed also to be cache line boundaries).
The effect of this is that architectures with non-coherent DMA caches may run into memory corruption or kernel crashes with Unhandled kernel unaligned accesses exceptions.
Fix the alignment by positioning the DMA area in front of the allocation and use memory at the end of the area for storing the orginal transfer_buffer pointer. This may have the added benefit of increased performance as the DMA area is now fully aligned on all architectures.
Tested with Lantiq xRX200 (MIPS) and RPi Model B Rev 2 (ARM).
Fixes: 3bc04e28a030 ("usb: dwc2: host: Get aligned DMA in a more supported way") Cc: stable@vger.kernel.org Reviewed-by: Douglas Anderson dianders@chromium.org Signed-off-by: Antti Seppälä a.seppala@gmail.com Signed-off-by: Felipe Balbi felipe.balbi@linux.intel.com --- drivers/usb/dwc2/hcd.c | 44 ++++++++++++++++++++++-------------------- 1 file changed, 23 insertions(+), 21 deletions(-)
diff --git a/drivers/usb/dwc2/hcd.c b/drivers/usb/dwc2/hcd.c index b1104be3429c..2ed0ac18e053 100644 --- a/drivers/usb/dwc2/hcd.c +++ b/drivers/usb/dwc2/hcd.c @@ -2665,34 +2665,29 @@ static int dwc2_alloc_split_dma_aligned_buf(struct dwc2_hsotg *hsotg,
#define DWC2_USB_DMA_ALIGN 4
-struct dma_aligned_buffer { - void *kmalloc_ptr; - void *old_xfer_buffer; - u8 data[0]; -}; - static void dwc2_free_dma_aligned_buffer(struct urb *urb) { - struct dma_aligned_buffer *temp; + void *stored_xfer_buffer;
if (!(urb->transfer_flags & URB_ALIGNED_TEMP_BUFFER)) return;
- temp = container_of(urb->transfer_buffer, - struct dma_aligned_buffer, data); + /* Restore urb->transfer_buffer from the end of the allocated area */ + memcpy(&stored_xfer_buffer, urb->transfer_buffer + + urb->transfer_buffer_length, sizeof(urb->transfer_buffer));
if (usb_urb_dir_in(urb)) - memcpy(temp->old_xfer_buffer, temp->data, + memcpy(stored_xfer_buffer, urb->transfer_buffer, urb->transfer_buffer_length); - urb->transfer_buffer = temp->old_xfer_buffer; - kfree(temp->kmalloc_ptr); + kfree(urb->transfer_buffer); + urb->transfer_buffer = stored_xfer_buffer;
urb->transfer_flags &= ~URB_ALIGNED_TEMP_BUFFER; }
static int dwc2_alloc_dma_aligned_buffer(struct urb *urb, gfp_t mem_flags) { - struct dma_aligned_buffer *temp, *kmalloc_ptr; + void *kmalloc_ptr; size_t kmalloc_size;
if (urb->num_sgs || urb->sg || @@ -2700,22 +2695,29 @@ static int dwc2_alloc_dma_aligned_buffer(struct urb *urb, gfp_t mem_flags) !((uintptr_t)urb->transfer_buffer & (DWC2_USB_DMA_ALIGN - 1))) return 0;
- /* Allocate a buffer with enough padding for alignment */ + /* + * Allocate a buffer with enough padding for original transfer_buffer + * pointer. This allocation is guaranteed to be aligned properly for + * DMA + */ kmalloc_size = urb->transfer_buffer_length + - sizeof(struct dma_aligned_buffer) + DWC2_USB_DMA_ALIGN - 1; + sizeof(urb->transfer_buffer);
kmalloc_ptr = kmalloc(kmalloc_size, mem_flags); if (!kmalloc_ptr) return -ENOMEM;
- /* Position our struct dma_aligned_buffer such that data is aligned */ - temp = PTR_ALIGN(kmalloc_ptr + 1, DWC2_USB_DMA_ALIGN) - 1; - temp->kmalloc_ptr = kmalloc_ptr; - temp->old_xfer_buffer = urb->transfer_buffer; + /* + * Position value of original urb->transfer_buffer pointer to the end + * of allocation for later referencing + */ + memcpy(kmalloc_ptr + urb->transfer_buffer_length, + &urb->transfer_buffer, sizeof(urb->transfer_buffer)); + if (usb_urb_dir_out(urb)) - memcpy(temp->data, urb->transfer_buffer, + memcpy(kmalloc_ptr, urb->transfer_buffer, urb->transfer_buffer_length); - urb->transfer_buffer = temp->data; + urb->transfer_buffer = kmalloc_ptr;
urb->transfer_flags |= URB_ALIGNED_TEMP_BUFFER;