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

[Roger Pau Monné <roger.pau%citrix.com@localhost>]

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

From: =?ISO-8859-1?Q?Roger_Pau_Monn=E9?= <roger.pau%citrix.com@localhost>
To: Manuel Bouyer <bouyer%antioche.eu.org@localhost>
Cc: "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>, "royger%netbsd.org@localhost" 
<royger%NetBSD.org@localhost>
Subject: Re: port-xen/47057: Xen NetBSD DomU file system trash under Linux
 Dom0
Date: Sat, 20 Oct 2012 17:48:08 +0200

 On 20/10/12 17:38, Manuel Bouyer wrote:
 > On Sat, Oct 20, 2012 at 05:31:11PM +0200, Roger Pau Monné wrote:
 >>> You can also try to type 'continue' and enter ddb again to see
 >>> if things changes (especially where in xenbus_thread it is
 >>> interrupted).
 >>
 >> Nope, the system is completely frozen, tried several times and the trace
 >> is exactly the same.
 > 
 > You mean, it's always at xenbus_thread+0xf5 ? You never see other offsets ?
 
 No, no other offsets.
 
 > 
 >> Will compile a new kernel with -g and let's see
 >> what I can get, but I bet xenbus_thread is blocked at:
 >>
 >> 831: printk("XENBUS error %d while reading message\n", err);
 >>
 >> In fact I'm going to replace that with a panic.
 > 
 > Maybe just a printf instead of a printk at first.
 
 Tried that in the past (replacing the printk with a printf), and then I
 just get in an infite printf loop, intf->rsp_cons and intf->rsp_prod are
 corrupted, check_indexes in xb_read always returns false and this leads
 to a infinite loop in xenbus_thread because process_msg always return error.
 
 I've now compiled a kernel that has the panic and prints the ring
 indexes. What's the best way to check who modifies intf->rsp_cons and
 intf->rsp_prod? Will ddb watch work on this kind of memory region?
 
 > If the offset never changes, I wonder if it could be stuck in
 >      (void)HYPERVISOR_console_io(CONSOLEIO_write, ret, buf);
 >