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=-10.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=unavailable 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 6F49DC43461 for ; Tue, 11 May 2021 13:45:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4293A61363 for ; Tue, 11 May 2021 13:45:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231671AbhEKNrA (ORCPT ); Tue, 11 May 2021 09:47:00 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38728 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231426AbhEKNq6 (ORCPT ); Tue, 11 May 2021 09:46:58 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 44459C06174A; Tue, 11 May 2021 06:45:52 -0700 (PDT) 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=FVA5wqZqu8qiAE18h5kq9MiEIAMhp9EbfMLzX4fyri0=; b=qXaafalpgCsxtOTMTKsFr32oAl Ey4Pn5q26OmCtYaucXBxnIc0nTRX90wkfOgcbYJ5B9wESM8C0n7F3PTXHnwa4/4MY5QSTyVNzOt2w w0LE/RGFPT2Iwwi983+WJrOchbqG2Z/ZhzM+nFrlyFr/Yd475x75jCjPe0Kbh06tm93HqeyDPJ7SS 39BS3YUqzv/AbpzCUfG8+HXbylR9cj/X15Ad3l0g9OfyanhsU7zCJw8gAxfCVgsxRaDJ1igUR85M6 CriaKnychXfPzkvEMBUYFiJI1YXfFtIFEjJMyv/0jqIWfCze7IKMWonff8JCfJMI48b3ANGJBXgfp R6vqWoeA==; Received: from willy by casper.infradead.org with local (Exim 4.94 #2 (Red Hat Linux)) id 1lgShY-007K8j-G2; Tue, 11 May 2021 13:45:33 +0000 Date: Tue, 11 May 2021 14:45:32 +0100 From: Matthew Wilcox To: Matteo Croce Cc: netdev@vger.kernel.org, linux-mm@kvack.org, Ayush Sawal , Vinay Kumar Yadav , Rohit Maheshwari , "David S. Miller" , Jakub Kicinski , Thomas Petazzoni , Marcin Wojtas , Russell King , Mirko Lindner , Stephen Hemminger , Tariq Toukan , Jesper Dangaard Brouer , Ilias Apalodimas , Alexei Starovoitov , Daniel Borkmann , John Fastabend , Boris Pismenny , Arnd Bergmann , Andrew Morton , "Peter Zijlstra (Intel)" , Vlastimil Babka , Yu Zhao , Will Deacon , Michel Lespinasse , Fenghua Yu , Roman Gushchin , Hugh Dickins , Peter Xu , Jason Gunthorpe , Jonathan Lemon , Alexander Lobakin , Cong Wang , wenxu , Kevin Hao , Jakub Sitnicki , Marco Elver , Willem de Bruijn , Miaohe Lin , Yunsheng Lin , Guillaume Nault , linux-kernel@vger.kernel.org, linux-rdma@vger.kernel.org, bpf@vger.kernel.org, Eric Dumazet , David Ahern , Lorenzo Bianconi , Saeed Mahameed , Andrew Lunn , Paolo Abeni , Sven Auhagen Subject: Re: [PATCH net-next v4 1/4] mm: add a signature in struct page Message-ID: References: <20210511133118.15012-1-mcroce@linux.microsoft.com> <20210511133118.15012-2-mcroce@linux.microsoft.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210511133118.15012-2-mcroce@linux.microsoft.com> Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Tue, May 11, 2021 at 03:31:15PM +0200, Matteo Croce wrote: > @@ -101,6 +101,7 @@ struct page { > * 32-bit architectures. > */ > unsigned long dma_addr[2]; > + unsigned long signature; > }; > struct { /* slab, slob and slub */ > union { No. Signature now aliases with page->mapping, which is going to go badly wrong for drivers which map this page into userspace. I had this as: + unsigned long pp_magic; + unsigned long xmi; + unsigned long _pp_mapping_pad; unsigned long dma_addr[2]; and pp_magic needs to be set to something with bits 0&1 clear and clearly isn't a pointer. I went with POISON_POINTER_DELTA + 0x40.