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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,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 4750CC28CC7 for ; Mon, 10 Jun 2019 12:32:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 27F7720679 for ; Mon, 10 Jun 2019 12:32:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389471AbfFJMcu (ORCPT ); Mon, 10 Jun 2019 08:32:50 -0400 Received: from verein.lst.de ([213.95.11.211]:43628 "EHLO newverein.lst.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2389048AbfFJMcu (ORCPT ); Mon, 10 Jun 2019 08:32:50 -0400 Received: by newverein.lst.de (Postfix, from userid 2407) id 4360268B02; Mon, 10 Jun 2019 14:32:22 +0200 (CEST) Date: Mon, 10 Jun 2019 14:32:22 +0200 From: Christoph Hellwig To: Yoshihiro Shimoda Cc: Christoph Hellwig , Alan Stern , Linux-Renesas , "linux-block@vger.kernel.org" , "iommu@lists.linux-foundation.org" , "linux-usb@vger.kernel.org" Subject: Re: How to resolve an issue in swiotlb environment? Message-ID: <20190610123222.GA20985@lst.de> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.17 (2007-11-01) Sender: linux-usb-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org Hi Yoshihiro, sorry for not taking care of this earlier, today is a public holiday here and thus I'm not working much over the long weekend. On Mon, Jun 10, 2019 at 11:13:07AM +0000, Yoshihiro Shimoda wrote: > I have another way to avoid the issue. But it doesn't seem that a good way though... > According to the commit that adding blk_queue_virt_boundary() [3], > this is needed for vhci_hcd as a workaround so that if we avoid to call it > on xhci-hcd driver, the issue disappeared. What do you think? > JFYI, I pasted a tentative patch in the end of email [4]. Oh, I hadn't even look at why USB uses blk_queue_virt_boundary, and it seems like the usage is wrong, as it doesn't follow the same rules as all the others. I think your patch goes in the right direction, but instead of comparing a hcd name it needs to be keyed of a flag set by the driver (I suspect there is one indicating native SG support, but I can't quickly find it), and we need an alternative solution for drivers that don't see like vhci. I suspect just limiting the entire transfer size to something that works for a single packet for them would be fine.