Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753470AbaJGKiB (ORCPT ); Tue, 7 Oct 2014 06:38:01 -0400 Received: from mta-out1.inet.fi ([62.71.2.197]:40925 "EHLO jenni2.inet.fi" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752758AbaJGKh6 (ORCPT ); Tue, 7 Oct 2014 06:37:58 -0400 Date: Tue, 7 Oct 2014 13:36:45 +0300 From: "Kirill A. Shutemov" To: Andrea Arcangeli Cc: qemu-devel@nongnu.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-api@vger.kernel.org, Linus Torvalds , Andres Lagar-Cavilla , Dave Hansen , Paolo Bonzini , Rik van Riel , Mel Gorman , Andy Lutomirski , Andrew Morton , Sasha Levin , Hugh Dickins , Peter Feiner , "\\\"Dr. David Alan Gilbert\\\"" , Christopher Covington , Johannes Weiner , Android Kernel Team , Robert Love , Dmitry Adamushko , Neil Brown , Mike Hommey , Taras Glek , Jan Kara , KOSAKI Motohiro , Michel Lespinasse , Minchan Kim , Keith Packard , "Huangpeng (Peter)" , Isaku Yamahata , Anthony Liguori , Stefan Hajnoczi , Wenchao Xia , Andrew Jones , Juan Quintela Subject: Re: [PATCH 08/17] mm: madvise MADV_USERFAULT Message-ID: <20141007103645.GB30762@node.dhcp.inet.fi> References: <1412356087-16115-1-git-send-email-aarcange@redhat.com> <1412356087-16115-9-git-send-email-aarcange@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1412356087-16115-9-git-send-email-aarcange@redhat.com> User-Agent: Mutt/1.5.22.1 (2013-10-16) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Oct 03, 2014 at 07:07:58PM +0200, Andrea Arcangeli wrote: > MADV_USERFAULT is a new madvise flag that will set VM_USERFAULT in the > vma flags. Whenever VM_USERFAULT is set in an anonymous vma, if > userland touches a still unmapped virtual address, a sigbus signal is > sent instead of allocating a new page. The sigbus signal handler will > then resolve the page fault in userland by calling the > remap_anon_pages syscall. Hm. I wounder if this functionality really fits madvise(2) interface: as far as I understand it, it provides a way to give a *hint* to kernel which may or may not trigger an action from kernel side. I don't think an application will behaive reasonably if kernel ignore the *advise* and will not send SIGBUS, but allocate memory. I would suggest to consider to use some other interface for the functionality: a new syscall or, perhaps, mprotect(). -- Kirill A. Shutemov -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/