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=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT 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 E1370C282D4 for ; Wed, 30 Jan 2019 08:02:11 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id A398121473 for ; Wed, 30 Jan 2019 08:02:11 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A398121473 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=lst.de Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 442468E0004; Wed, 30 Jan 2019 03:02:11 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 3F2738E0001; Wed, 30 Jan 2019 03:02:11 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 306F88E0004; Wed, 30 Jan 2019 03:02:11 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from mail-wr1-f72.google.com (mail-wr1-f72.google.com [209.85.221.72]) by kanga.kvack.org (Postfix) with ESMTP id CD6708E0001 for ; Wed, 30 Jan 2019 03:02:10 -0500 (EST) Received: by mail-wr1-f72.google.com with SMTP id j30so8923270wre.16 for ; Wed, 30 Jan 2019 00:02:10 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-original-authentication-results:x-gm-message-state:date:from:to :cc:subject:message-id:references:mime-version:content-disposition :in-reply-to:user-agent; bh=bSvzEOpTuQZUwQLSOSlYFpmxHnqbqpoLNfEkerIfslQ=; b=EW+pCGHM1MYwqfUQvxAYCbMnJfywycXmc4bNPn62QdyoVeCLQHg17YyvNMioobXsP2 UENkWnNueKcAdcoyXMysB/nevOD+EnI5bN/d4JaROyVlRWfZ/yjArUvIsc9gYs5RINvK Q7ijsTg1xE3xk2Qr1YU0lrDB+u5Ngl4QfqiU0gKA2rCb0LIXtKq2E6yaTm4l/paWJ67+ LqdoSIXmv+XnonAc8cjBT586ukwpkh7A1aB/ptOQEqmhUjXE387aik7v745x3gb5sdc4 /pyUZRbM09MyGOBpx4IsQ7imo4fxYpGxvyhLafDT+1NSP0E54uWFLi/x3+7BQwXGQky4 AumA== X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of hch@lst.de designates 213.95.11.211 as permitted sender) smtp.mailfrom=hch@lst.de X-Gm-Message-State: AJcUukeHevoC2jIzQLbyS7VHWMZNuIPjaBvxq9F+Ycg62uYnAY09DyYd K3N5TpIMyV9X05P128lFBlqpWdTwptgmHXNZzYlNdiDgHyfwXMB8+u5pADI4rQnf9zy2pu4pyta CsMcjcO43NFsFO8yF1BH0RMHebWfBzuZliWqlYbcN77i3j/AlTSKeWJOQ9qroE10yiQ== X-Received: by 2002:a1c:4346:: with SMTP id q67mr25464557wma.114.1548835330313; Wed, 30 Jan 2019 00:02:10 -0800 (PST) X-Google-Smtp-Source: ALg8bN560zrVod5boWlhdGeOc3GMa+0oMiPnimMeVmYtWWQogcIc3fzg9+2OjxV96m5dEfK7ehRt X-Received: by 2002:a1c:4346:: with SMTP id q67mr25464478wma.114.1548835329427; Wed, 30 Jan 2019 00:02:09 -0800 (PST) ARC-Seal: i=1; a=rsa-sha256; t=1548835329; cv=none; d=google.com; s=arc-20160816; b=YsyGCtuLJExUP7NUWhcS3tfya5fHQIKsZxAlqr+QscGWgF9AEg8AJSvXB1Z3ac1+u4 Ch0VxMXtinTEYByy+/YtDhKKLaYX/ugZKUKTOZNoaGahbLKyfODM147tN6O2BN+/a71N nKYStO9lW//5AaxmRNldkHthyToH4UotDJRK0X5GQifrcZ6vi/WDNyX7Sl3DyEXGuFW3 kvnHZdleFNLj7ez9BbHYwRycVWyDXKX5bqg8nwsrolksWIBgoN7ikm9zUOpzGU2ynJXU h6f1Pa8UlQk1PmSuAoy2K5LRBeq0jjmGZtrbQEQHjDOAidozdGgFtK0KTDmRwuSDSCRe jNBw== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=user-agent:in-reply-to:content-disposition:mime-version:references :message-id:subject:cc:to:from:date; bh=bSvzEOpTuQZUwQLSOSlYFpmxHnqbqpoLNfEkerIfslQ=; b=aBuSG/guPGORMb0Okd5LR0W7N2MLvMjvGL2J+h6xyskK9BwoUT6/TiEPnbBCoD4DtO 1H8wL05v5d2PHZ5Xl70kEard5T6/kn6udGmSTGsCYFN0n8DNLE4IasByiBob5iwenvqy bRf+Nhq2nNq+7kntXzuRXz4296DC90cY387knEqyWo76FYu/eche2APoyWeToFRmf8UL JkHrK58HPVhzx2e7Vn3DzgeRG2Xr2DhcIeUtegu/J6ZqiCFjigYeR17GWe6UaQ6KvHHI Q/63C3BZ+ZWoyVv9u12jy7rfptXl670vtHn/LOKBe6E4/7p9/5cOkR9T4LOH9J4J0cZz 3Ibg== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: best guess record for domain of hch@lst.de designates 213.95.11.211 as permitted sender) smtp.mailfrom=hch@lst.de Received: from newverein.lst.de (verein.lst.de. [213.95.11.211]) by mx.google.com with ESMTPS id l17si890142wmi.103.2019.01.30.00.02.09 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 30 Jan 2019 00:02:09 -0800 (PST) Received-SPF: pass (google.com: best guess record for domain of hch@lst.de designates 213.95.11.211 as permitted sender) client-ip=213.95.11.211; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of hch@lst.de designates 213.95.11.211 as permitted sender) smtp.mailfrom=hch@lst.de Received: by newverein.lst.de (Postfix, from userid 2407) id BF4D968CEC; Wed, 30 Jan 2019 09:02:08 +0100 (CET) Date: Wed, 30 Jan 2019 09:02:08 +0100 From: Christoph Hellwig To: Jason Gunthorpe Cc: Logan Gunthorpe , Jerome Glisse , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , Greg Kroah-Hartman , "Rafael J . Wysocki" , Bjorn Helgaas , Christian Koenig , Felix Kuehling , "linux-pci@vger.kernel.org" , "dri-devel@lists.freedesktop.org" , Christoph Hellwig , Marek Szyprowski , Robin Murphy , Joerg Roedel , "iommu@lists.linux-foundation.org" Subject: Re: [RFC PATCH 3/5] mm/vma: add support for peer to peer to device vma Message-ID: <20190130080208.GC29665@lst.de> References: <20190129174728.6430-1-jglisse@redhat.com> <20190129174728.6430-4-jglisse@redhat.com> <20190129191120.GE3176@redhat.com> <20190129193250.GK10108@mellanox.com> <99c228c6-ef96-7594-cb43-78931966c75d@deltatee.com> <20190129205827.GM10108@mellanox.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190129205827.GM10108@mellanox.com> User-Agent: Mutt/1.5.17 (2007-11-01) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, Jan 29, 2019 at 08:58:35PM +0000, Jason Gunthorpe wrote: > On Tue, Jan 29, 2019 at 01:39:49PM -0700, Logan Gunthorpe wrote: > > > implement the mapping. And I don't think we should have 'special' vma's > > for this (though we may need something to ensure we don't get mapping > > requests mixed with different types of pages...). > > I think Jerome explained the point here is to have a 'special vma' > rather than a 'special struct page' as, really, we don't need a > struct page at all to make this work. > > If I recall your earlier attempts at adding struct page for BAR > memory, it ran aground on issues related to O_DIRECT/sgls, etc, etc. Struct page is what makes O_DIRECT work, using sgls or biovecs, etc on it work. Without struct page none of the above can work at all. That is why we use struct page for backing BARs in the existing P2P code. Not that I'm a particular fan of creating struct page for this device memory, but without major invasive surgery to large parts of the kernel it is the only way to make it work.