From mboxrd@z Thu Jan 1 00:00:00 1970 From: Zachary Amsden Subject: Re: [PATCH 0/5] KVM paravirt_ops implementation Date: Wed, 20 Jun 2007 13:43:03 -0700 Message-ID: <46799157.3070805@vmware.com> References: <4675F462.1010708@codemonkey.ws> <4675F9DE.6080806@goop.org> <4675FDCA.4040006@codemonkey.ws> <4676084F.3090901@goop.org> <46787325.30804@vmware.com> <4679381E.9090404@codemonkey.ws> <46794899.6070708@goop.org> <46798174.2060304@vmware.com> <46798597.4020903@codemonkey.ws> <4679882B.7070605@vmware.com> <46798B16.5090407@goop.org> <46798D9B.5000400@codemonkey.ws> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <46798D9B.5000400-rdkfGonbjUSkNkDKm+mE6A@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org Errors-To: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org To: Anthony Liguori Cc: Jeremy Fitzhardinge , kvm-devel , virtualization List-Id: virtualization@lists.linuxfoundation.org Anthony Liguori wrote: > I've been thinking about this wrt the hypercall page in KVM. The > problem is that in a model like KVM (or presumably VMI), migration > gets really difficult if you have anything but a trivial hypercall > page since the hypercall page will change after migration. > > If you cannot guarantee the guest isn't executing code within the > hypercall page (or in your case, doing something with paravirt_ops), > then you cannot safely migrate. Unless you also migrate the hypercall page itself and impose migration restrictions on compatible hypercall pages. Although I favor the guarantee that execution within the hypercall page is finished - it is important for protecting against non-reentrancy as well. Think about interrupts during batching / queueing operations. Zach ------------------------------------------------------------------------- This SF.net email is sponsored by DB2 Express Download DB2 Express C - the FREE version of DB2 express and take control of your XML. No limits. Just data. Click to get it now. http://sourceforge.net/powerbar/db2/