From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D8E72C31E40 for ; Tue, 6 Aug 2019 15:11:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id AC7FE20717 for ; Tue, 6 Aug 2019 15:11:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1565104310; bh=6UDrRhYrOs/0fVNeFUa7B2/tVmvKcooNzy/lwG+cCG0=; h=Subject:To:Cc:References:From:Date:In-Reply-To:List-ID:From; b=OyZbZCjYrvNfnN/uEsCgkRkRg1+JFsHuWJL/yVr9hcJuVqwAXstJKDze02UTEpiBV yWmPrzvwSWrTG7ESceofKamLLY5zVTLzIKucl9gSt8nNy7lFJZZo1qbIHmZdifG7n3 QUV70U9MU/0z1cw4GB3EFrBZ3vU76vndIygclv8s= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732024AbfHFPLq (ORCPT ); Tue, 6 Aug 2019 11:11:46 -0400 Received: from mail.kernel.org ([198.145.29.99]:56780 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726713AbfHFPLp (ORCPT ); Tue, 6 Aug 2019 11:11:45 -0400 Received: from [192.168.1.112] (c-24-9-64-241.hsd1.co.comcast.net [24.9.64.241]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id BCA9F2089E; Tue, 6 Aug 2019 15:11:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1565104305; bh=6UDrRhYrOs/0fVNeFUa7B2/tVmvKcooNzy/lwG+cCG0=; h=Subject:To:Cc:References:From:Date:In-Reply-To:From; b=k6IBJzQx9Arxu9foQUy+C1P4gaB9mQ07b842qiWcYyMDUu8gNQN6rq7QT9uRCAvCb 8wEWWuGOGCTnGaGo3VBmag8BLg/EVF0Td+PCzKJ6fstT7C43cnYrGl8W0nztAj+aw4 cCjlwkwKoMmSn8gmQFpAvOh3Y348vzvNBshV5wno= Subject: Re: [PATCH v4 1/2] usbip: Skip DMA mapping and unmapping for urb at vhci To: Suwan Kim , valentina.manea.m@gmail.com, gregkh@linuxfoundation.org, stern@rowland.harvard.edu Cc: linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, shuah References: <20190806123154.23798-1-suwan.kim027@gmail.com> <20190806123154.23798-2-suwan.kim027@gmail.com> From: shuah Message-ID: Date: Tue, 6 Aug 2019 09:11:30 -0600 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <20190806123154.23798-2-suwan.kim027@gmail.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-usb-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org On 8/6/19 6:31 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 > --- > v3 - v4: > - Replace WARN_ON() with pr_err() in the error path. > > v2 - v3 > - Move setting URB_DMA_MAP_SG flag to the patch 2. > - Prevent isoc pipe from using SG buffer. > > v1 - v2 > - Add setting URB_DMA_MAP_SG flag in urb->transfer_flags to tell > stub driver to use SG buffer. > --- > 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..429e4e989f38 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) { > + pr_err("SG is not supported for isochronous transfer\n"); Any reason to not use dev_err()? Looks good otherwise. thanks, -- Shuah