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=-5.1 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,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 E4DB4C5517A for ; Mon, 9 Nov 2020 16:47:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6E724221E9 for ; Mon, 9 Nov 2020 16:47:26 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=deltatee.com header.i=@deltatee.com header.b="J7+Mv2hm" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730631AbgKIQrZ (ORCPT ); Mon, 9 Nov 2020 11:47:25 -0500 Received: from ale.deltatee.com ([204.191.154.188]:32996 "EHLO ale.deltatee.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729776AbgKIQrZ (ORCPT ); Mon, 9 Nov 2020 11:47:25 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=deltatee.com; s=20200525; h=Subject:Content-Transfer-Encoding:Content-Type: In-Reply-To:MIME-Version:Date:Message-ID:From:References:Cc:To:Sender: Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From:Resent-Sender :Resent-To:Resent-Cc:Resent-Message-ID:List-Id:List-Help:List-Unsubscribe: List-Subscribe:List-Post:List-Owner:List-Archive; bh=M+FlpbSeF5MJfdXFDHCsfOBW2uUFOxuE0dG6gfttals=; b=J7+Mv2hmxQ4d09bkdoSjlqM2hY vOukZfUTBRpLH8UGn1KHGgk0N/mPDRhd8A08oEOiCCh7q0cCAQVeglBNPPwfDNvy1V8uyt6Yu6ZUv B226XvqReVoUsnygDkmcgOzKoZH3chhJ0pctPMiVhnGnBjWg9+3MBnhgwV0R2hIc8OBD0D4YeHHv3 0EhQ5E/lzpaFxooyniSTwwoOSq1y/+/a4VGSBpzogy8zYQeSpf0UXlcEzEqG/fRetW7/w+rJj2q0x 1m0DXzXIw3LJaLolwWEGKvxt4TbNZ8TqfPtxCyHuIFLEYgVlgR1OZb3qgvysUDswJ3GahxJvXZhyY skh+Vrug==; Received: from guinness.priv.deltatee.com ([172.16.1.162]) by ale.deltatee.com with esmtp (Exim 4.92) (envelope-from ) id 1kcAK2-00011d-Rd; Mon, 09 Nov 2020 09:47:15 -0700 To: Christoph Hellwig Cc: linux-kernel@vger.kernel.org, linux-nvme@lists.infradead.org, linux-block@vger.kernel.org, linux-pci@vger.kernel.org, linux-mm@kvack.org, iommu@lists.linux-foundation.org, Stephen Bates , Dan Williams , Jason Gunthorpe , =?UTF-8?Q?Christian_K=c3=b6nig?= , Ira Weiny , John Hubbard , Don Dutile , Matthew Wilcox , Daniel Vetter References: <20201106170036.18713-1-logang@deltatee.com> <20201106170036.18713-5-logang@deltatee.com> <20201109091258.GB28918@lst.de> From: Logan Gunthorpe Message-ID: <4e336c7e-207b-31fa-806e-c4e8028524a5@deltatee.com> Date: Mon, 9 Nov 2020 09:47:11 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.3.1 MIME-Version: 1.0 In-Reply-To: <20201109091258.GB28918@lst.de> Content-Type: text/plain; charset=utf-8 Content-Language: en-CA Content-Transfer-Encoding: 7bit X-SA-Exim-Connect-IP: 172.16.1.162 X-SA-Exim-Rcpt-To: daniel.vetter@ffwll.ch, willy@infradead.org, ddutile@redhat.com, jhubbard@nvidia.com, iweiny@intel.com, christian.koenig@amd.com, jgg@ziepe.ca, dan.j.williams@intel.com, sbates@raithlin.com, iommu@lists.linux-foundation.org, linux-mm@kvack.org, linux-pci@vger.kernel.org, linux-block@vger.kernel.org, linux-nvme@lists.infradead.org, linux-kernel@vger.kernel.org, hch@lst.de X-SA-Exim-Mail-From: logang@deltatee.com Subject: Re: [RFC PATCH 04/15] lib/scatterlist: Add flag for indicating P2PDMA segments in an SGL X-SA-Exim-Version: 4.2.1 (built Wed, 08 May 2019 21:11:16 +0000) X-SA-Exim-Scanned: Yes (on ale.deltatee.com) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2020-11-09 2:12 a.m., 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. Yes, I expected this would be the unacceptable part. Any alternative ideas? Logan