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 00802C31E40 for ; Tue, 6 Aug 2019 15:39:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C7650216B7 for ; Tue, 6 Aug 2019 15:39:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1565105941; bh=WSyjZn+YLypg21sFQeIjJZqQbHjw3ecOVTDeasZ6QE4=; h=Subject:To:Cc:References:From:Date:In-Reply-To:List-ID:From; b=MUQCm1aUrzSerVGCtUIW/svTD72XOOs8FgWWoYJ88A6r4stmq6YKzG8Pb/+Byj7Yh c3i+w76rzDFZX8Bv10nxod3D5JuJUsMqwUgMWLPrg/oXHh5aNTAGwn/vAO7FXd5sKw YjWa3227UsaL6uXzIVWN7+etqvSCU03LXZa6LE+M= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729680AbfHFPi5 (ORCPT ); Tue, 6 Aug 2019 11:38:57 -0400 Received: from mail.kernel.org ([198.145.29.99]:38706 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728156AbfHFPi5 (ORCPT ); Tue, 6 Aug 2019 11:38:57 -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 3D2CE20717; Tue, 6 Aug 2019 15:38:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1565105935; bh=WSyjZn+YLypg21sFQeIjJZqQbHjw3ecOVTDeasZ6QE4=; h=Subject:To:Cc:References:From:Date:In-Reply-To:From; b=Chbn1UpOQSIkiQmbmfnz3vY2T8w8jfDOCzP60WH3GSv0NCvXaMV8z0zV9S+9hCPLM YiUjcVLXt0gPO43bEiCiabBpUk/0K+RcdnKhupjr7PerFPsJBW8hAraqI7RCqNfjZ8 8aaNHzq1Fjl0qmJhFlOgNBRzmHjjZoYSaHQTbIj8= Subject: Re: [PATCH v4 1/2] usbip: Skip DMA mapping and unmapping for urb at vhci To: Suwan Kim Cc: valentina.manea.m@gmail.com, gregkh@linuxfoundation.org, stern@rowland.harvard.edu, 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> <20190806153241.GA3738@localhost.localdomain> From: shuah Message-ID: Date: Tue, 6 Aug 2019 09:38:54 -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: <20190806153241.GA3738@localhost.localdomain> 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 9:32 AM, Suwan Kim wrote: > On Tue, Aug 06, 2019 at 09:11:30AM -0600, shuah wrote: >> 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()? > > Because some codes in vhci_hcd.c use pr_err().There is no other > reason. However, dev_err() seems more appropriate than pr_err(). > I will replace pr_err() with dev_err(urb->dev->dev, "SG is ...") > Is it ok? > Please. This way we will have the device information. pr_err() won't us that. In general I prefer dev_* if dev is available in the code path, which is the case here. thanks, -- Shuah