From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f72.google.com (mail-wm0-f72.google.com [74.125.82.72]) by kanga.kvack.org (Postfix) with ESMTP id 603F46B038C for ; Sat, 18 Mar 2017 13:01:19 -0400 (EDT) Received: by mail-wm0-f72.google.com with SMTP id h188so8663390wma.4 for ; Sat, 18 Mar 2017 10:01:19 -0700 (PDT) Received: from mail-wr0-x243.google.com (mail-wr0-x243.google.com. [2a00:1450:400c:c0c::243]) by mx.google.com with ESMTPS id i63si7711969wmd.135.2017.03.18.10.01.17 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sat, 18 Mar 2017 10:01:17 -0700 (PDT) Received: by mail-wr0-x243.google.com with SMTP id u108so13037934wrb.2 for ; Sat, 18 Mar 2017 10:01:17 -0700 (PDT) Date: Wed, 15 Mar 2017 18:42:05 +0300 From: "Kirill A. Shutemov" Subject: Re: [PATCH 0/6] x86: 5-level paging enabling for v4.12, Part 1 Message-ID: <20170315154205.33hvpvkbjypgkd7g@node.shutemov.name> References: <20170313143309.16020-1-kirill.shutemov@linux.intel.com> <20170314074729.GA23151@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org List-ID: To: Linus Torvalds Cc: Ingo Molnar , "Kirill A. Shutemov" , Andrew Morton , the arch/x86 maintainers , Thomas Gleixner , Ingo Molnar , Arnd Bergmann , "H. Peter Anvin" , Andi Kleen , Dave Hansen , Andy Lutomirski , Michal Hocko , "linux-arch@vger.kernel.org" , linux-mm , Linux Kernel Mailing List On Tue, Mar 14, 2017 at 10:48:51AM -0700, Linus Torvalds wrote: > On Tue, Mar 14, 2017 at 12:47 AM, Ingo Molnar wrote: > > > > I've also applied the GUP patch, with the assumption that you'll address Linus's > > request to switch x86 over to the generic version. > > Note that switching over to the generic version is somewhat fraught > with subtle issues: > > (a) we need to make sure that x86 actually matches the required > semantics for the generic GUP. > > (b) we need to make sure the atomicity of the page table reads is ok. > > (c) need to verify the maximum VM address properly There's another difference with generic version: it uses page_cache_get_speculative() instead of plain get_page() on x86. That's somewhat more expensive, but probably fine. -- Kirill A. Shutemov -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org