From mboxrd@z Thu Jan 1 00:00:00 1970 From: Keir Fraser Subject: Re: Re: [PATCH] Support swap a page from user spacetools -- Was RE: [RFC][PATCH] Basic support for page offline Date: Fri, 20 Mar 2009 09:42:24 +0000 Message-ID: References: <49C37206.76E4.0078.0@novell.com> Mime-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <49C37206.76E4.0078.0@novell.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: Jan Beulich , Yunhong Jiang Cc: Tim Deegan , "xen-devel@lists.xensource.com" List-Id: xen-devel@lists.xenproject.org On 20/03/2009 09:37, "Jan Beulich" wrote: >> 5) After update all page tables, user space tools will try to exchange the >> old page with the new page. If the new mfn has no >> reference anymore (i.e. count_info & count_mask = 1), the exchange will >> update the m2p and return success, otherwise it will >> return fail. (the page may be referenced by other domain, like grant table or >> foreign mapped). > > Hmm, if you consider the possibility of this case, then you should also > consider the possibility of a page still being accessible by another domain at > the point where you copy its content, but no longer in use when you do the > exchange (which means that the content may have changed between the two points > in time). Since the guest is suspended, would that matter? Any I/Os that were in flight on suspend will get resubmitted on resume. So the potential races might all be benign. -- Keir