On Tue, Aug 27, 2019 at 12:00:07AM +0900, Suwan Kim wrote: > There are bugs on vhci with usb 3.0 storage device. In USB, each SG > list entry buffer should be divisible by the bulk max packet size. > But with native SG support, this problem doesn't matter because the > SG buffer is treated as contiguous buffer. But without native SG > support, USB storage driver breaks SG list into several URBs and the > error occurs because of a buffer size of URB that cannot be divided > by the bulk max packet size. The error situation is as follows. > > When USB Storage driver requests 31.5 KB data and has SG list which > has 3584 bytes buffer followed by 7 4096 bytes buffer for some > reason. USB Storage driver splits this SG list into several URBs > because VHCI doesn't support SG and sends them separately. So the > first URB buffer size is 3584 bytes. When receiving data from device, > USB 3.0 device sends data packet of 1024 bytes size because the max > packet size of BULK pipe is 1024 bytes. So device sends 4096 bytes. > But the first URB buffer has only 3584 bytes buffer size. So host > controller terminates the transfer even though there is more data to > receive. So, vhci needs to support SG transfer to prevent this error. > > In this patch, vhci supports SG regardless of whether the server's > host controller supports SG or not, because stub driver splits SG > list into several URBs if the server's host controller doesn't > support SG. > > To support SG, vhci sets URB_DMA_MAP_SG flag in urb->transfer_flags > if URB has SG list and this flag will tell stub driver to use SG > list. After receiving urb from stub driver, vhci clear URB_DMA_MAP_SG > flag to avoid dma unmapping in HCD. I have a mistake not modifying this commit log according to the change of the code. I will resend v8. Regards Suwan Kim
