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=-2.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, 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 C3AA4C35247 for ; Mon, 3 Feb 2020 17:11:08 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 785D020721 for ; Mon, 3 Feb 2020 17:11:08 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="IEhxI504" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 785D020721 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 2223E6B0692; Mon, 3 Feb 2020 12:11:08 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 1D3EB6B0693; Mon, 3 Feb 2020 12:11:08 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 074466B0694; Mon, 3 Feb 2020 12:11:08 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0209.hostedemail.com [216.40.44.209]) by kanga.kvack.org (Postfix) with ESMTP id DF91B6B0692 for ; Mon, 3 Feb 2020 12:11:07 -0500 (EST) Received: from smtpin03.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 90FD0180AD80F for ; Mon, 3 Feb 2020 17:11:07 +0000 (UTC) X-FDA: 76449456174.03.ice63_7e20b608edd48 X-HE-Tag: ice63_7e20b608edd48 X-Filterd-Recvd-Size: 9429 Received: from us-smtp-delivery-1.mimecast.com (us-smtp-1.mimecast.com [207.211.31.81]) by imf13.hostedemail.com (Postfix) with ESMTP for ; Mon, 3 Feb 2020 17:11:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1580749866; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:autocrypt:autocrypt; bh=OCy8r+VxWXTJgkiB5bVYIPDHOx7WbPgsXxqFjuY5cMw=; b=IEhxI5048v2Qe8FeOSGL66aQsluXvBchDJb9XOGIK1HQMe58x5PDa1WyKCRWKCbTTDSmqR D2xg4dg2rWEhJo9VCUZs6Uy9Te2ZnHeICl27k5uuC3Au0PnyF0F3HQOKkgbqs6t6qN9aS8 FAhYnsMD6GITporcSXCMu1X3i3JJtQ4= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-207-EATBlwwbMbiMr0tXLapQjQ-1; Mon, 03 Feb 2020 12:10:57 -0500 X-MC-Unique: EATBlwwbMbiMr0tXLapQjQ-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 3034318B9FE1; Mon, 3 Feb 2020 17:10:55 +0000 (UTC) Received: from [10.36.117.77] (ovpn-117-77.ams2.redhat.com [10.36.117.77]) by smtp.corp.redhat.com (Postfix) with ESMTP id B4C805D9CA; Mon, 3 Feb 2020 17:10:50 +0000 (UTC) Subject: Re: [PATCH 09/16] page-flags: define PG_reserved behavior on compound pages To: Chris Wilson , "Kirill A. Shutemov" Cc: "Kirill A. Shutemov" , Andrea Arcangeli , Andrew Morton , Hugh Dickins , Dave Hansen , Mel Gorman , Vlastimil Babka , Christoph Lameter , Naoya Horiguchi , Steve Capper , "Aneesh Kumar K.V" , Johannes Weiner , Michal Hocko , Jerome Marchand , linux-kernel@vger.kernel.org, linux-mm@kvack.org References: <1426784902-125149-1-git-send-email-kirill.shutemov@linux.intel.com> <1426784902-125149-10-git-send-email-kirill.shutemov@linux.intel.com> <158048425224.2430.4905670949721797624@skylake-alporthouse-com> <20200203151844.mmgcwzz3igo7h6wj@box> <158074345183.25650.17229941243604183055@skylake-alporthouse-com> From: David Hildenbrand Autocrypt: addr=david@redhat.com; prefer-encrypt=mutual; keydata= mQINBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABtCREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT6JAlgEEwEIAEICGwMFCQlmAYAGCwkIBwMCBhUI AgkKCwQWAgMBAh4BAheAFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAl3pImkCGQEACgkQTd4Q 9wD/g1o+VA//SFvIHUAvul05u6wKv/pIR6aICPdpF9EIgEU448g+7FfDgQwcEny1pbEzAmiw zAXIQ9H0NZh96lcq+yDLtONnXk/bEYWHHUA014A1wqcYNRY8RvY1+eVHb0uu0KYQoXkzvu+s Dncuguk470XPnscL27hs8PgOP6QjG4jt75K2LfZ0eAqTOUCZTJxA8A7E9+XTYuU0hs7QVrWJ jQdFxQbRMrYz7uP8KmTK9/Cnvqehgl4EzyRaZppshruKMeyheBgvgJd5On1wWq4ZUV5PFM4x II3QbD3EJfWbaJMR55jI9dMFa+vK7MFz3rhWOkEx/QR959lfdRSTXdxs8V3zDvChcmRVGN8U Vo93d1YNtWnA9w6oCW1dnDZ4kgQZZSBIjp6iHcA08apzh7DPi08jL7M9UQByeYGr8KuR4i6e RZI6xhlZerUScVzn35ONwOC91VdYiQgjemiVLq1WDDZ3B7DIzUZ4RQTOaIWdtXBWb8zWakt/ ztGhsx0e39Gvt3391O1PgcA7ilhvqrBPemJrlb9xSPPRbaNAW39P8ws/UJnzSJqnHMVxbRZC Am4add/SM+OCP0w3xYss1jy9T+XdZa0lhUvJfLy7tNcjVG/sxkBXOaSC24MFPuwnoC9WvCVQ ZBxouph3kqc4Dt5X1EeXVLeba+466P1fe1rC8MbcwDkoUo65Ag0EVcufkQEQAOfX3n0g0fZz Bgm/S2zF/kxQKCEKP8ID+Vz8sy2GpDvveBq4H2Y34XWsT1zLJdvqPI4af4ZSMxuerWjXbVWb T6d4odQIG0fKx4F8NccDqbgHeZRNajXeeJ3R7gAzvWvQNLz4piHrO/B4tf8svmRBL0ZB5P5A 2uhdwLU3NZuK22zpNn4is87BPWF8HhY0L5fafgDMOqnf4guJVJPYNPhUFzXUbPqOKOkL8ojk CXxkOFHAbjstSK5Ca3fKquY3rdX3DNo+EL7FvAiw1mUtS+5GeYE+RMnDCsVFm/C7kY8c2d0G NWkB9pJM5+mnIoFNxy7YBcldYATVeOHoY4LyaUWNnAvFYWp08dHWfZo9WCiJMuTfgtH9tc75 7QanMVdPt6fDK8UUXIBLQ2TWr/sQKE9xtFuEmoQGlE1l6bGaDnnMLcYu+Asp3kDT0w4zYGsx 5r6XQVRH4+5N6eHZiaeYtFOujp5n+pjBaQK7wUUjDilPQ5QMzIuCL4YjVoylWiBNknvQWBXS lQCWmavOT9sttGQXdPCC5ynI+1ymZC1ORZKANLnRAb0NH/UCzcsstw2TAkFnMEbo9Zu9w7Kv AxBQXWeXhJI9XQssfrf4Gusdqx8nPEpfOqCtbbwJMATbHyqLt7/oz/5deGuwxgb65pWIzufa N7eop7uh+6bezi+rugUI+w6DABEBAAGJAiUEGAECAA8FAlXLn5ECGwwFCQlmAYAACgkQTd4Q 9wD/g1qA6w/+M+ggFv+JdVsz5+ZIc6MSyGUozASX+bmIuPeIecc9UsFRatc91LuJCKMkD9Uv GOcWSeFpLrSGRQ1Z7EMzFVU//qVs6uzhsNk0RYMyS0B6oloW3FpyQ+zOVylFWQCzoyyf227y GW8HnXunJSC+4PtlL2AY4yZjAVAPLK2l6mhgClVXTQ/S7cBoTQKP+jvVJOoYkpnFxWE9pn4t H5QIFk7Ip8TKr5k3fXVWk4lnUi9MTF/5L/mWqdyIO1s7cjharQCstfWCzWrVeVctpVoDfJWp 4LwTuQ5yEM2KcPeElLg5fR7WB2zH97oI6/Ko2DlovmfQqXh9xWozQt0iGy5tWzh6I0JrlcxJ ileZWLccC4XKD1037Hy2FLAjzfoWgwBLA6ULu0exOOdIa58H4PsXtkFPrUF980EEibUp0zFz GotRVekFAceUaRvAj7dh76cToeZkfsjAvBVb4COXuhgX6N4pofgNkW2AtgYu1nUsPAo+NftU CxrhjHtLn4QEBpkbErnXQyMjHpIatlYGutVMS91XTQXYydCh5crMPs7hYVsvnmGHIaB9ZMfB njnuI31KBiLUks+paRkHQlFcgS2N3gkRBzH7xSZ+t7Re3jvXdXEzKBbQ+dC3lpJB0wPnyMcX FOTT3aZT7IgePkt5iC/BKBk3hqKteTnJFeVIT7EC+a6YUFg= Organization: Red Hat GmbH Message-ID: Date: Mon, 3 Feb 2020 18:10:49 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.3.1 MIME-Version: 1.0 In-Reply-To: <158074345183.25650.17229941243604183055@skylake-alporthouse-com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Content-Transfer-Encoding: quoted-printable 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 03.02.20 16:24, Chris Wilson wrote: > Quoting Kirill A. Shutemov (2020-02-03 15:18:44) >> On Fri, Jan 31, 2020 at 03:24:12PM +0000, Chris Wilson wrote: >>> Quoting Kirill A. Shutemov (2015-03-19 17:08:15) >>>> As far as I can see there's no users of PG_reserved on compound page= s. >>>> Let's use NO_COMPOUND here. >>> >>> Much later than you would ever expect, but we just had a user update = an >>> ancient device and trip over this. >>> https://gitlab.freedesktop.org/drm/intel/issues/1027 >>> >>> In drm_pci_alloc() we allocate a high-order page (for it to be physic= ally >>> contiguous) and mark each page as Reserved. >>> >>> dmah->vaddr =3D dma_alloc_coherent(&dev->pdev->dev, size, >>> &dmah->busaddr, >>> GFP_KERNEL | __GFP_COMP); >>> >>> /* XXX - Is virt_to_page() legal for consistent mem? */ >>> /* Reserve */ >>> for (addr =3D (unsigned long)dmah->vaddr, sz =3D size; >>> sz > 0; addr +=3D PAGE_SIZE, sz -=3D PAGE_SIZE) { >>> SetPageReserved(virt_to_page((void *)addr)); >>> } >>> >>> It's been doing that since >>> >>> commit ddf19b973be5a96d77c8467f657fe5bd7d126e0f >>> Author: Dave Airlie >>> Date: Sun Mar 19 18:56:12 2006 +1100 >>> >>> drm: fixup PCI DMA support >>> >>> I haven't found anything to say if we are meant to be reserving the >>> pages or not. So I bring it to your attention, asking for help. >> >> I don't see a real reason for these pages to be reserved. But I might = be >> wrong here. >> >> I tried to look around: other users (infiniband/ethernet) of >> dma_alloc_coherent(__GFP_COMP) don't mess with PG_reserved. >> >> Could you try to drop it from DRM? >=20 > That is the current plan. So long as there is nothing magical about > either the __GFP_COMP or SetPageReserved, we should be able to drop the= m > without any functional change. Only 2 very old bits of HW (r128, ancien= t > i915) depend on this routine, and i915 seems, touch wood, quite happy > with a plain dma_alloc_coherent(). I documented a while ago in include/linux/page-flags.h " Pages marked as PG_reserved include: [...] MMIO/DMA pages. Some architectures don't allow to ioremap pages that are not marked PG_reserved (as they might be in use by somebody else who does not respect the caching strategy). " I also removed a bunch of users back then (and even had a patch to remove this code here), but for this code I think I came to the conclusion that it might be relevant for some archs. git grep -o PageReserved | grep ioremap arch/mips/mm/ioremap.c:PageReserved arch/nios2/mm/ioremap.c:PageReserved arch/parisc/mm/ioremap.c:PageReserved arch/x86/mm/ioremap.c:PageReserved It would be good to clarify if this here is actually needed (and in addition the same pattern in other driver/ paths) and eventually update the documentation. --=20 Thanks, David / dhildenb