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=-8.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_MUTT 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 F10F1C31E49 for ; Wed, 19 Jun 2019 08:16:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CB3A52084A for ; Wed, 19 Jun 2019 08:16:53 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="M3qgtyV4" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731297AbfFSIQt (ORCPT ); Wed, 19 Jun 2019 04:16:49 -0400 Received: from mail-pg1-f196.google.com ([209.85.215.196]:44385 "EHLO mail-pg1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731213AbfFSIQt (ORCPT ); Wed, 19 Jun 2019 04:16:49 -0400 Received: by mail-pg1-f196.google.com with SMTP id n2so9202248pgp.11; Wed, 19 Jun 2019 01:16:48 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:content-transfer-encoding:in-reply-to :user-agent; bh=v129+ZmLYPT0Qs610F/+KFD490TqCFT77Vj5+nBNN28=; b=M3qgtyV4AQr65r2pR1XmxMysyqRVsRmXoqrZFpp9C6zTvsQyKmyphn+6AiqPxTOdAH GCRRu24W/izWtCCzJFP6u6UQieHtTtp0qqTrZexVYMkd7yTbbrh8vgbSrR4Kn4Vdg9+A QWg4sDNEf3lZe8+jA3hazKFgNMOAfdapUL9f3l+tdDT6CC4rd8MbUMPM+ZLX2NeF9rLt etQbZ+g8R4qczgqml/JlfBZM4KSiK0a4+k2efumXahIGq6HnPrLUjXEGfg91nT0xgt6l URrAu1aqdjXKyeUckE/effvcdPFBchJe7vjkuPnRqTprmS0TxjeCBmt3mAclkLSoXOfi jxQA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:content-transfer-encoding :in-reply-to:user-agent; bh=v129+ZmLYPT0Qs610F/+KFD490TqCFT77Vj5+nBNN28=; b=AmD9B1b7xlMziihkS0WSYzdbAutrJpSGWFHW7Qb9mDPb1V3L407cGQcdzBCkxAeDYJ G3r06BIkTigMc9WBkjVQigm83a0wZ3TKGGC1Gua+KT0tQfnQ/oBrOymhCGWLTUPkyryF RYlymmgdks/FZV/yXNZQOYeTwy6Wfkf8k60oEb+afdadTgy70KfAfHweKyS5e18fkD0x wGOvK7v1R/T4e5l8kgMNZ8mSMuzP9bPO7U9fZg9icWSybuAw7gmW8orHp8rv3pRnzWyY BSmqOiEGUec2YuMEKTa7OdTr9GgGcVJiU8D94X2tR5U/lgS12j85l60vC9NrUFJ/F5jd AJyw== X-Gm-Message-State: APjAAAUUdmTB3AbrbciIIa1dOR+JripUyBaNAq3zXafpi2CL60fyJ6pv SBGGCz0axizjKYZKWVv2ccg= X-Google-Smtp-Source: APXvYqy46mmCmfahU0kewqo7z+Wo2ByFUBKVQhnj602dEah1sJEMMpRJq+iwu/9ERzcbE0ZNLHP96A== X-Received: by 2002:a63:80c8:: with SMTP id j191mr6962738pgd.442.1560932208474; Wed, 19 Jun 2019 01:16:48 -0700 (PDT) Received: from localhost.localdomain ([163.152.162.99]) by smtp.gmail.com with ESMTPSA id u1sm15769414pgr.94.2019.06.19.01.16.46 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Wed, 19 Jun 2019 01:16:48 -0700 (PDT) Date: Wed, 19 Jun 2019 17:16:42 +0900 From: Suwan Kim To: Alan Stern Cc: shuah@kernel.org, valentina.manea.m@gmail.com, gregkh@linuxfoundation.org, linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] usbip: Implement map_urb_for_dma function for vhci to skip dma mapping Message-ID: <20190619081641.GA2387@localhost.localdomain> References: <20190618142817.16844-1-suwan.kim027@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-usb-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org On Tue, Jun 18, 2019 at 11:30:34AM -0400, Alan Stern wrote: > On Tue, 18 Jun 2019, Suwan Kim wrote: > > > vhci doesn’t do dma for remote device. Actually, the real dma > > operation is done by network card driver. So, vhci doesn’t use and > > need dma address of transfer buffer of urb. > > > > But hcd provides dma mapping function by defualt in usb_hcd_submit_urb() > > and it causes unnecessary dma mapping which will be done again at > > NIC driver and it wastes CPU cycles. So, implement map_urb_for_dma > > function for vhci in order to skip the dma mapping procedure. > > > > Signed-off-by: Suwan Kim > > --- > > drivers/usb/usbip/vhci_hcd.c | 8 ++++++++ > > 1 file changed, 8 insertions(+) > > > > diff --git a/drivers/usb/usbip/vhci_hcd.c b/drivers/usb/usbip/vhci_hcd.c > > index 667d9c0ec905..9df4d9e36788 100644 > > --- a/drivers/usb/usbip/vhci_hcd.c > > +++ b/drivers/usb/usbip/vhci_hcd.c > > @@ -1287,6 +1287,13 @@ 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) > > +{ > > + dev_dbg(hcd->self.controller, "vhci does not map urb for dma\n"); > > + return 0; > > +} > > + > > static const struct hc_driver vhci_hc_driver = { > > .description = driver_name, > > .product_desc = driver_desc, > > @@ -1302,6 +1309,7 @@ static const struct hc_driver vhci_hc_driver = { > > .urb_dequeue = vhci_urb_dequeue, > > > > .get_frame_number = vhci_get_frame_number, > > + .map_urb_for_dma = vhci_map_urb_for_dma, > > > > .hub_status_data = vhci_hub_status, > > .hub_control = vhci_hub_control, > > If the goal is to avoid wasting CPU cycles, you probably should have a > vhci_unmap_urb_for_dma routine as well. I missed that. Thank you for pointing it out. I will send v2 including unmap function. Regards Suwan Kim