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=-15.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham 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 AD002C433E6 for ; Thu, 28 Jan 2021 18:20:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 79D3464DE5 for ; Thu, 28 Jan 2021 18:20:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231876AbhA1STo (ORCPT ); Thu, 28 Jan 2021 13:19:44 -0500 Received: from verein.lst.de ([213.95.11.211]:58507 "EHLO verein.lst.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231506AbhA1SQp (ORCPT ); Thu, 28 Jan 2021 13:16:45 -0500 Received: by verein.lst.de (Postfix, from userid 2407) id B320468B02; Thu, 28 Jan 2021 19:15:58 +0100 (CET) Date: Thu, 28 Jan 2021 19:15:57 +0100 From: Christoph Hellwig To: Robin Murphy Cc: Jianxiong Gao , erdemaktas@google.com, marcorr@google.com, hch@lst.de, m.szyprowski@samsung.com, gregkh@linuxfoundation.org, saravanak@google.com, heikki.krogerus@linux.intel.com, rafael.j.wysocki@intel.com, andriy.shevchenko@linux.intel.com, dan.j.williams@intel.com, bgolaszewski@baylibre.com, jroedel@suse.de, iommu@lists.linux-foundation.org, konrad.wilk@oracle.com, kbusch@kernel.org, axboe@fb.com, sagi@grimberg.me, linux-nvme@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/3] Adding page_offset_mask to device_dma_parameters Message-ID: <20210128181557.GA11790@lst.de> References: <20210128003829.1892018-1-jxgao@google.com> <20210128003829.1892018-2-jxgao@google.com> <2863b6d2-47f6-51fa-f60c-ba24904818e9@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <2863b6d2-47f6-51fa-f60c-ba24904818e9@arm.com> User-Agent: Mutt/1.5.17 (2007-11-01) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jan 28, 2021 at 05:27:25PM +0000, Robin Murphy wrote: > On 2021-01-28 00:38, Jianxiong Gao wrote: >> Some devices rely on the address offset in a page to function >> correctly (NVMe driver as an example). These devices may use >> a different page size than the Linux kernel. The address offset >> has to be preserved upon mapping, and in order to do so, we >> need to record the page_offset_mask first. >> >> Signed-off-by: Jianxiong Gao >> --- >> include/linux/device.h | 1 + >> include/linux/dma-mapping.h | 17 +++++++++++++++++ >> 2 files changed, 18 insertions(+) >> >> diff --git a/include/linux/device.h b/include/linux/device.h >> index 1779f90eeb4c..f44e0659fc66 100644 >> --- a/include/linux/device.h >> +++ b/include/linux/device.h >> @@ -292,6 +292,7 @@ struct device_dma_parameters { >> */ >> unsigned int max_segment_size; >> unsigned long segment_boundary_mask; >> + unsigned int page_offset_mask; > > Could we call this something more like "min_align_mask" (sorry, I can't > think of a name that's actually good and descriptive right now). > Essentially I worry that having "page" in there is going to be too easy to > misinterpret as having anything to do what "page" means almost everywhere > else (even before you throw IOMMU pages into the mix). > > Also note that of all the possible ways to pack two ints and a long, this > one is the worst ;) The block layer uses virt_boundary for the related concept, but that is pretty horrible too.