From: Jeremy Fitzhardinge Subject: Re: Interaction between Xen and XFS: stray RW mappings Date: Mon, 22 Oct 2007 11:37:49 -0700 Message-ID: <471CEDFD.3030603@goop.org> References: <470FA7C3.90404@goop.org> <471C1A61.1010001@goop.org> <200710221439.21503.nickpiggin@yahoo.com.au> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <200710221439.21503.nickpiggin@yahoo.com.au> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: Nick Piggin Cc: Xen-devel , =?ISO-8859-1?Q?Morten_?=, dean gaudet , Linux Kernel Mailing List , =?ISO-8859-1?Q?B=F8geskov?= , xfs@oss.sgi.com, xfs-masters@oss.sgi.com, David Chinner , Mark Williamson List-Id: xen-devel@lists.xenproject.org Nick Piggin wrote: > You could call it a bug I think. I don't know much about Xen though, > whether or not it expects to be able to run an arbitrary OS kernel. > Xen's paravirtualized mode always requires a guest OS to be modified; certainly some operating systems would be very hard to make work with Xen. But you can always fall back to using shadow pagetables or full hvm (VT/SVM) mode. > Presumably, the hypervisor _could_ write protect and trap writes to > *all* page table page mappings. > Xen manages this stuff with refcounts; it doesn't maintain an rmap for these pages, so it would have to exhaustively search to do this. But aside from that, Xen never actively modifies pagetables, so this would be a new behaviour in the interface. J