From mboxrd@z Thu Jan 1 00:00:00 1970 From: Derek Murray Subject: Re: Re: Next steps with pv_ops for Xen Date: Wed, 05 Dec 2007 17:48:49 +0000 Message-ID: <4756E481.1060201@cl.cam.ac.uk> References: Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: Keir Fraser Cc: "xen-devel@lists.xensource.com" , Eduardo Habkost , Juan Quintela , "Stephen C. Tweedie" , Jan Beulich , Glauber de Oliveira Costa , Chris Wright , "virtualization@lists.osdl.org" , Gerd Hoffmann List-Id: virtualization@lists.linuxfoundation.org Keir Fraser wrote: > Need to bite the bullet and fix this properly by setting a software flag in > ptes that are not subject to reference counting. Could we get away with testing the VM_FOREIGN flag in vm_normal_page()? Although I get the impression that this wouldn't be easily justified if trying to merge with upstream Linux.... > Unfortunately that also needs a hypervisor interface change, to allow > setting of those pte flags. Easily done though, and we should definitely get > that piece in for 3.2.0. Alternatively, could we use the _PAGE_GNTTAB PTE flag that is used for debugging? Indeed, if we did this, could be obviate the need for the PTE-zapping hook, by instead catching the case where this flag is set, and unmapping the grant implicitly? Otherwise, what would the semantics of this new flag be? Regards, Derek.