Messages in this thread | | | Subject | Re: [PATCH v3 1/2] usbip: Skip DMA mapping and unmapping for urb at vhci | From | shuah <> | Date | Mon, 5 Aug 2019 09:08:18 -0600 |
| |
On 8/4/19 11:23 PM, Suwan Kim wrote: > On Fri, Aug 02, 2019 at 04:22:27PM -0600, shuah wrote: >> On 8/2/19 11:36 AM, Suwan Kim wrote: >>> vhci doesn’t do DMA for remote device. Actually, the real DMA >>> operation is done by network card driver. vhci just passes virtual >>> address of the buffer to the network stack, so vhci doesn’t use and >>> need dma address of the buffer of the URB. >>> >>> But HCD provides DMA mapping and unmapping function by default. >>> Moreover, it causes unnecessary DMA mapping and unmapping which >>> will be done again at the NIC driver and it wastes CPU cycles. >>> So, implement map_urb_for_dma and unmap_urb_for_dma function for >>> vhci in order to skip the DMA mapping and unmapping procedure. >>> >>> When it comes to supporting SG for vhci, it is useful to use native >>> SG list (urb->num_sgs) instead of mapped SG list because DMA mapping >>> fnuction can adjust the number of SG list (urb->num_mapped_sgs). >>> And vhci_map_urb_for_dma() prevents isoc pipe from using SG as >>> hcd_map_urb_for_dma() does. >>> >>> Signed-off-by: Suwan Kim <suwan.kim027@gmail.com> >>> --- >>> drivers/usb/usbip/vhci_hcd.c | 19 +++++++++++++++++++ >>> 1 file changed, 19 insertions(+) >>> >>> diff --git a/drivers/usb/usbip/vhci_hcd.c b/drivers/usb/usbip/vhci_hcd.c >>> index 000ab7225717..c62f7fa8118c 100644 >>> --- a/drivers/usb/usbip/vhci_hcd.c >>> +++ b/drivers/usb/usbip/vhci_hcd.c >>> @@ -1288,6 +1288,22 @@ static int vhci_free_streams(struct usb_hcd *hcd, struct usb_device *udev, >>> return 0; >>> } >>> +static int vhci_map_urb_for_dma(struct usb_hcd *hcd, struct urb *urb, >>> + gfp_t mem_flags) >>> +{ >>> + if (usb_endpoint_xfer_isoc(&urb->ep->desc) && urb->num_sgs) { >>> + WARN_ON(1); >> >> Don't add WARN_ON. I cleaned them all up recently and don't want new >> ones added. > > Ok. I will remove it and resend v4. >
Please add appropriate error message in place of WARN_ON
thanks, -- Shuah
| |