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=-5.3 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no 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 BAFF3C2D0A3 for ; Mon, 9 Nov 2020 14:02:32 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 523EC20867 for ; Mon, 9 Nov 2020 14:02:32 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="ozmOWgQh" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 523EC20867 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.20170209; h=Sender:Content-Type: Content-Transfer-Encoding:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:Date:Message-ID:From: References:To:Subject:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=lafiJtYz6azJyImy9Fs5KrEKkKA+dP+RtMh2O/hB+4g=; b=ozmOWgQhvw2AvDqLAWFdD6Qoc C1ttrk6liKAoJpJtHiZ3L/Z/x+2t+lDUOn/Pdl77u8ckn2SdhT8VlcWBFbEjWS2aLITI9v//JcEma rwpe6GFDlb3OoyIb9eW7KCJ0pXYEIC7OQ9RfnPYmvcjik3WXDENow7/b6zWHJxz315V8YSYoGE1xn wNJMGpEhCHNZIoJRWwcy5uPB54WPGD4cHcjCWxBsjY5VhDQ7dluXz/9fS3xov1Wv4IO4RGxNnKZtT LKCXZlbDzuQ89Id0hnGVJapRL/8Bx0LJUVKoAsqPRxYu3g1N0wu3xD1vmvCSW5qnjCJGTkzygXhIb /h2Eb5K4A==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1kc7kb-0001FK-6Z; Mon, 09 Nov 2020 14:02:29 +0000 Received: from foss.arm.com ([217.140.110.172]) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1kc7kY-0001EI-Sj for linux-nvme@lists.infradead.org; Mon, 09 Nov 2020 14:02:27 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 8C77E31B; Mon, 9 Nov 2020 06:02:25 -0800 (PST) Received: from [10.57.54.223] (unknown [10.57.54.223]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 383D53F719; Mon, 9 Nov 2020 06:02:23 -0800 (PST) Subject: Re: [RFC PATCH 04/15] lib/scatterlist: Add flag for indicating P2PDMA segments in an SGL To: Christoph Hellwig , Logan Gunthorpe References: <20201106170036.18713-1-logang@deltatee.com> <20201106170036.18713-5-logang@deltatee.com> <20201109091258.GB28918@lst.de> From: Robin Murphy Message-ID: <491c26de-bda0-3266-a67d-ee2580559a54@arm.com> Date: Mon, 9 Nov 2020 14:02:21 +0000 User-Agent: Mozilla/5.0 (Windows NT 10.0; rv:78.0) Gecko/20100101 Thunderbird/78.4.1 MIME-Version: 1.0 In-Reply-To: <20201109091258.GB28918@lst.de> Content-Language: en-GB X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20201109_090227_055036_43CD1E34 X-CRM114-Status: GOOD ( 15.09 ) X-BeenThere: linux-nvme@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: John Hubbard , linux-mm@kvack.org, Daniel Vetter , Ira Weiny , linux-kernel@vger.kernel.org, Matthew Wilcox , Stephen Bates , linux-block@vger.kernel.org, Jason Gunthorpe , iommu@lists.linux-foundation.org, linux-nvme@lists.infradead.org, linux-pci@vger.kernel.org, Dan Williams , =?UTF-8?Q?Christian_K=c3=b6nig?= Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "Linux-nvme" Errors-To: linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org On 2020-11-09 09:12, Christoph Hellwig wrote: > On Fri, Nov 06, 2020 at 10:00:25AM -0700, Logan Gunthorpe wrote: >> We make use of the top bit of the dma_length to indicate a P2PDMA >> segment. > > I don't think "we" can. There is nothing limiting the size of a SGL > segment. Right, the story behind ab2cbeb0ed30 ("iommu/dma: Handle SG length overflow better") comes immediately to mind, for one. If all the P2P users can agree to be in on the game then by all means implement this in the P2P code, but I don't think it belongs in the generic top-level scatterlist API. Robin. _______________________________________________ Linux-nvme mailing list Linux-nvme@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-nvme