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=HEADER_FROM_DIFFERENT_DOMAINS, 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 3A4F6C18E5B for ; Tue, 17 Mar 2020 12:28:19 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 00DF7206EC for ; Tue, 17 Mar 2020 12:28:18 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 00DF7206EC 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 789CF6B0005; Tue, 17 Mar 2020 08:28:18 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 71B416B0006; Tue, 17 Mar 2020 08:28:18 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 659736B0007; Tue, 17 Mar 2020 08:28:18 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0099.hostedemail.com [216.40.44.99]) by kanga.kvack.org (Postfix) with ESMTP id 521D96B0005 for ; Tue, 17 Mar 2020 08:28:18 -0400 (EDT) Received: from smtpin22.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 06416181AEF09 for ; Tue, 17 Mar 2020 12:28:18 +0000 (UTC) X-FDA: 76604781876.22.sound55_e321af3d9c28 X-HE-Tag: sound55_e321af3d9c28 X-Filterd-Recvd-Size: 2857 Received: from verein.lst.de (verein.lst.de [213.95.11.211]) by imf24.hostedemail.com (Postfix) with ESMTP for ; Tue, 17 Mar 2020 12:28:17 +0000 (UTC) Received: by verein.lst.de (Postfix, from userid 2407) id 1763568BFE; Tue, 17 Mar 2020 13:28:14 +0100 (CET) Date: Tue, 17 Mar 2020 13:28:13 +0100 From: Christoph Hellwig To: Jason Gunthorpe Cc: Ralph Campbell , Christoph Hellwig , Dan Williams , Bharata B Rao , Christian =?iso-8859-1?Q?K=F6nig?= , Ben Skeggs , Jerome Glisse , kvm-ppc@vger.kernel.org, amd-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, nouveau@lists.freedesktop.org, linux-mm@kvack.org Subject: Re: [PATCH 3/4] mm: simplify device private page handling in hmm_range_fault Message-ID: <20200317122813.GA11866@lst.de> References: <20200316193216.920734-1-hch@lst.de> <20200316193216.920734-4-hch@lst.de> <7256f88d-809e-4aba-3c46-a223bd8cc521@nvidia.com> <20200317121536.GQ20941@ziepe.ca> <20200317122445.GA11662@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200317122445.GA11662@lst.de> 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, Mar 17, 2020 at 01:24:45PM +0100, Christoph Hellwig wrote: > On Tue, Mar 17, 2020 at 09:15:36AM -0300, Jason Gunthorpe wrote: > > > Getting rid of HMM_PFN_DEVICE_PRIVATE seems reasonable to me since a driver can > > > look at the struct page but what if a driver needs to fault in a page from > > > another device's private memory? Should it call handle_mm_fault()? > > > > Isn't that what this series basically does? > > > > The dev_private_owner is set to the type of pgmap the device knows how > > to handle, and everything else is automatically faulted for the > > device. > > > > If the device does not know how to handle device_private then it sets > > dev_private_owner to NULL and it never gets device_private pfns. > > > > Since the device_private pfn cannot be dma mapped, drivers must have > > explicit support for them. > > No, with this series (and all actual callers before this series) > we never fault in device private pages. IFF we want to fault it in we'd need something like this. But I'd really prefer to see test cases for that first. diff --git a/mm/hmm.c b/mm/hmm.c index b75b3750e03d..2884a3d11a1f 100644 --- a/mm/hmm.c +++ b/mm/hmm.c @@ -276,7 +276,7 @@ static int hmm_vma_handle_pte(struct mm_walk *walk, unsigned long addr, if (!fault && !write_fault) return 0; - if (!non_swap_entry(entry)) + if (!non_swap_entry(entry) || is_device_private_entry(entry)) goto fault; if (is_migration_entry(entry)) {