From mboxrd@z Thu Jan 1 00:00:00 1970 From: Razvan Cojocaru Subject: Re: [PATCH V2] mem_event: Allow emulating an instruction that caused a page fault Date: Tue, 22 Jan 2013 16:22:16 +0200 Message-ID: <50FEA098.6030105@gmail.com> References: <50FDCBA8.1060000@gmail.com> <20130122123149.GA86613@ocelot.phlegethon.org> <50FE8BDD.9080504@gmail.com> <20130122132059.GA87324@ocelot.phlegethon.org> <50FE9876.8030907@gmail.com> <7A228E53-E6F8-4C1A-8BAF-F7558600FB5B@gridcentric.ca> Mime-Version: 1.0 Content-Type: text/plain; charset="windows-1252"; Format="flowed" Content-Transfer-Encoding: quoted-printable Return-path: In-Reply-To: <7A228E53-E6F8-4C1A-8BAF-F7558600FB5B@gridcentric.ca> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Andres Lagar-Cavilla Cc: Tim Deegan , "xen-devel@lists.xen.org" List-Id: xen-devel@lists.xenproject.org > Razvan, have you tried the n2rwx mode? It'll cause an event for the first= access to each page. It'll automatically patch the access (hence 2 rwx) to= allow execution to continue unhindered. > > So user-space doesn't decide anything, but gets informed about everything= (within the constraints of mem event, i.e. no foreign mappings, no Xen map= pings). Hello, yes, I did look at that. Unfortunately, my userspace application = needs to be notified about subsequent writes to the same page, and once = the page goes to rwx mode there are no further events. So that's not a = very useful mechanism. > If you want to know about every write and decide on every write=85 you ca= n't have your cake and eat it too, right? Right. Thanks, Razvan Cojocaru