From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail203.messagelabs.com (mail203.messagelabs.com [216.82.254.243]) by kanga.kvack.org (Postfix) with SMTP id 88FBF6B005D for ; Wed, 6 May 2009 13:09:15 -0400 (EDT) Date: Wed, 6 May 2009 10:09:17 -0700 From: Chris Wright Subject: Re: [PATCH 3/6] ksm: change the KSM_REMOVE_MEMORY_REGION ioctl. Message-ID: <20090506170917.GE15712@x200.localdomain> References: <1241475935-21162-1-git-send-email-ieidus@redhat.com> <1241475935-21162-2-git-send-email-ieidus@redhat.com> <1241475935-21162-3-git-send-email-ieidus@redhat.com> <1241475935-21162-4-git-send-email-ieidus@redhat.com> <4A00DF9B.1080501@redhat.com> <4A014C7B.9080702@redhat.com> <4A01AC5E.6000906@redhat.com> <20090506161424.GC15712@x200.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org To: Hugh Dickins Cc: Chris Wright , Izik Eidus , Rik van Riel , akpm@linux-foundation.org, linux-kernel@vger.kernel.org, aarcange@redhat.com, alan@lxorguk.ukuu.org.uk, device@lanana.org, linux-mm@kvack.org, nickpiggin@yahoo.com.au List-ID: * Hugh Dickins (hugh@veritas.com) wrote: > On Wed, 6 May 2009, Chris Wright wrote: > > Another > > question of what to do w/ VM_LOCKED, should that exclude VM_MERGE or > > let user get what asked for? > > What's the issue with VM_LOCKED? We wouldn't want to merge a page > while it was under get_user_pages (unless KSM's own, but ignore that), > but what's the deal with VM_LOCKED? > > Is the phrase "covert channel" going to come up somehow? There's two (still hand wavy) conerns I see there. First is the security implication: timing writes to see cow and guess the shared data for another apps VM_LOCKED region, second is just plain old complaints of those rt latency sensitive apps that somehow have VM_LOCKED|VM_MERGE and complain of COW fault time, probably just "don't do that". thanks, -chris -- 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