Re: port-xen/47057: Xen NetBSD DomU file system trash under Linux Dom0

[Manuel Bouyer <bouyer%antioche.eu.org@localhost>]

The following reply was made to PR port-xen/47057; it has been noted by GNATS.

From: Manuel Bouyer <bouyer%antioche.eu.org@localhost>
To: Roger Pau =?iso-8859-1?Q?Monn=E9?= <royger%NetBSD.org@localhost>
Cc: Roger Pau =?iso-8859-1?Q?Monn=E9?= <roger.pau%citrix.com@localhost>,
        "gnats-bugs%NetBSD.org@localhost" <gnats-bugs%NetBSD.org@localhost>,
        "port-xen-maintainer%netbsd.org@localhost" 
<port-xen-maintainer%NetBSD.org@localhost>,
        "gnats-admin%netbsd.org@localhost" <gnats-admin%NetBSD.org@localhost>,
        "netbsd-bugs%netbsd.org@localhost" <netbsd-bugs%NetBSD.org@localhost>
Subject: Re: port-xen/47057: Xen NetBSD DomU file system trash under Linux
 Dom0
Date: Sun, 21 Oct 2012 20:00:21 +0200

 On Sun, Oct 21, 2012 at 07:47:38PM +0200, Roger Pau Monné wrote:
 > On Sun, Oct 21, 2012 at 1:29 PM, Manuel Bouyer 
 > <bouyer%antioche.eu.org@localhost> wrote:
 > > OK, here's another patch, which also checks that the mapping doesn't
 > > change. But I wonder is the corruption occurs on the NetBSD side.
 > > Could you also add some debugging code on the other side ?
 > 
 > Still no luck with the new patch, I've been looking at the Linux code,
 > and the attached patch (taken the idea from Linux) mitigates the
 > problem, but we still have it.
 
 Does linux do this silently, or does it complain when the ring
 corruption occurs ?
 
 > I've also added the trace and verbose
 > options to xenstored running in the Dom0, and there's no sign that
 > anyone is writing to xenstore when the crash happens.
 > 
 > Is it possible that someone writes to the machine address
 > xen_start_info.store_mfn and is there anyway to check that nobody is
 > mapping this ma to another va?
 
 I've been thinking about checking this, but it's harder to do.
 Maybe it's easier to do this check in the hypervisor ?
 
 -- 
 Manuel Bouyer <bouyer%antioche.eu.org@localhost>
      NetBSD: 26 ans d'experience feront toujours la difference
 --