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=-3.9 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS 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 09DE5C2D0A3 for ; Wed, 4 Nov 2020 16:41:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A60C3206DB for ; Wed, 4 Nov 2020 16:41:22 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="Y1htN0aB" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731106AbgKDQlW (ORCPT ); Wed, 4 Nov 2020 11:41:22 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38352 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730971AbgKDQlV (ORCPT ); Wed, 4 Nov 2020 11:41:21 -0500 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C2FC6C0613D3; Wed, 4 Nov 2020 08:41:21 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=N+PdC8aIRIGAg2FR28I1P/4kBIo6jnmN4QhPRmCU08A=; b=Y1htN0aBJKelZ9PF10bOpkfzNm AbdmBX7uwg/dy8j86ohk0c2kPpXPZzG0w5faSlS/dCeaixKVHRJuLcLLQ7dQcHXbInbLBAAwWbgY2 0+jbViIJWH+PzBiBQWi2s9Jrmk/I8R62cvYgsYWRhrqxOhT5cze01WusTw+gBleoPF6GUkV4wguSf GN2jz0PJcmRTFJ9I/UNw0GwSXF3aEF7PE7twMLwlKVN5jr+K8DmA/zIiIGLLHLjPRHUvfri1ifWkQ lhzs6zF6PkoS5rz5oqYfTnpenyuB+ufAq0MXJl0XWojaqOVac3o65QNUxwOqel58DO/Tkmn/n4Rzl T1oYFK8w==; Received: from hch by casper.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1kaLqZ-0004uc-8m; Wed, 04 Nov 2020 16:41:19 +0000 Date: Wed, 4 Nov 2020 16:41:19 +0000 From: Christoph Hellwig To: Daniel Vetter Cc: Christoph Hellwig , Jason Gunthorpe , J??r??me Glisse , linux-samsung-soc , Jan Kara , Pawel Osciak , KVM list , John Hubbard , Mauro Carvalho Chehab , LKML , DRI Development , Tomasz Figa , Linux MM , Kyungmin Park , Daniel Vetter , Andrew Morton , Marek Szyprowski , Dan Williams , Linux ARM , "open list:DMA BUFFER SHARING FRAMEWORK" Subject: Re: [PATCH v5 05/15] mm/frame-vector: Use FOLL_LONGTERM Message-ID: <20201104164119.GA18218@infradead.org> References: <1f7cf690-35e2-c56f-6d3f-94400633edd2@nvidia.com> <7f29a42a-c408-525d-90b7-ef3c12b5826c@nvidia.com> <20201104140023.GQ36674@ziepe.ca> <20201104162125.GA13007@infradead.org> <20201104163758.GA17425@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201104163758.GA17425@infradead.org> X-SRS-Rewrite: SMTP reverse-path rewritten from by casper.infradead.org. See http://www.infradead.org/rpr.html Precedence: bulk List-ID: X-Mailing-List: linux-samsung-soc@vger.kernel.org On Wed, Nov 04, 2020 at 04:37:58PM +0000, Christoph Hellwig wrote: > On Wed, Nov 04, 2020 at 05:26:58PM +0100, Daniel Vetter wrote: > > What we're discussing is whether gup_fast and pup_fast also obey this, > > or fall over and can give you the struct page that's backing the > > dma_mmap_* memory. Since the _fast variant doesn't check for > > vma->vm_flags, and afaict that's the only thing which closes this gap. > > And like you restate, that would be a bit a problem. So where's that > > check which Jason&me aren't spotting? > > remap_pte_range uses pte_mkspecial to set up the PTEs, and gup_pte_range > errors out on pte_special. Of course this only works for the > CONFIG_ARCH_HAS_PTE_SPECIAL case, for other architectures we do have > a real problem. Except that we don't really support pte-level gup-fast without CONFIG_ARCH_HAS_PTE_SPECIAL, and in fact all architectures selecting HAVE_FAST_GUP also select ARCH_HAS_PTE_SPECIAL, so we should be fine.