Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754066AbXJVEp6 (ORCPT ); Mon, 22 Oct 2007 00:45:58 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751188AbXJVEpu (ORCPT ); Mon, 22 Oct 2007 00:45:50 -0400 Received: from smtp108.mail.mud.yahoo.com ([209.191.85.218]:25732 "HELO smtp108.mail.mud.yahoo.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1751139AbXJVEpu (ORCPT ); Mon, 22 Oct 2007 00:45:50 -0400 DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=s1024; d=yahoo.com.au; h=Received:X-YMail-OSG:From:To:Subject:Date:User-Agent:Cc:References:In-Reply-To:MIME-Version:Content-Type:Content-Transfer-Encoding:Content-Disposition:Message-Id; b=POTxb7XtXDXVXF5OmqUaS+Q1uOttvO41sgih9zniHHooeCWFQMsgSADrNWCNRPI88dsI3jP6SGwLTW/vnD0Ew6PEuj9OAGMl8amKO1442F45WUIO/MKXpftUB4345IfbCxPcL0iuGF4rXemigiub9Y74dAXXFk8nv23FPNILyo0= ; X-YMail-OSG: unlB55wVM1nPPiI5CbLS5NcaytrpQ60oVcWjYaZimQkAkIDWqxOu07p0A5sw3tzQPZjuU3xk2Q-- From: Nick Piggin To: dean gaudet Subject: Re: Interaction between Xen and XFS: stray RW mappings Date: Mon, 22 Oct 2007 14:39:21 +1000 User-Agent: KMail/1.9.5 Cc: Jeremy Fitzhardinge , David Chinner , xfs@oss.sgi.com, Xen-devel , Linux Kernel Mailing List , Mark Williamson , Morten =?iso-8859-1?q?B=F8geskov?= , xfs-masters@oss.sgi.com References: <470FA7C3.90404@goop.org> <471C1A61.1010001@goop.org> In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200710221439.21503.nickpiggin@yahoo.com.au> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1174 Lines: 26 On Monday 22 October 2007 14:28, dean gaudet wrote: > On Sun, 21 Oct 2007, Jeremy Fitzhardinge wrote: > > dean gaudet wrote: > > > On Mon, 15 Oct 2007, Nick Piggin wrote: > > >> Yes, as Dave said, vmap (more specifically: vunmap) is very expensive > > >> because it generally has to invalidate TLBs on all CPUs. > > > > > > why is that? ignoring 32-bit archs we have heaps of address space > > > available... couldn't the kernel just burn address space and delay > > > global TLB invalidate by some relatively long time (say 1 second)? > > > > Yes, that's precisely the problem. xfs does delay the unmap, leaving > > stray mappings, which upsets Xen. > > sounds like a bug in xen to me :) 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. Presumably, the hypervisor _could_ write protect and trap writes to *all* page table page mappings. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/