NetBSD Problem Report #47056

From  Thu Oct 11 17:03:47 2012
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Date: Thu, 11 Oct 2012 17:03:46 +0000 (UTC)
Subject: Xen NetBSD DomU freeze under Linux Dom0
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>Number:         47056
>Category:       port-xen
>Synopsis:       Xen NetBSD DomU freeze under Linux Dom0
>Confidential:   no
>Severity:       serious
>Priority:       high
>Responsible:    port-xen-maintainer
>State:          closed
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Thu Oct 11 17:05:00 +0000 2012
>Closed-Date:    Fri Nov 30 09:29:31 +0000 2012
>Last-Modified:  Fri Nov 30 09:29:31 +0000 2012
>Originator:     Roger Pau Monné
>Release:        6.0RC2
NetBSD  6.0_RC2 NetBSD 6.0_RC2 (XEN3_DOMU) #6: Wed Sep 26 18:06:29 BST 2012  root@roger-xen:/root/obj/sys/arch/amd64/compile/XEN3_DOMU amd64
The simptoms are that
the DomU is frozen and xentop on Dom0 shows CPU usage of 100% (so it's a
busy-wait). I went further on this, and the culprit of the freeze was
this line in sys/arch/xen/xenbus/xenbus_xs.c:

831 printk("XENBUS error %d while reading message\n", err);

Going further, replacing this line with a regular panic made the kernel
panic (obvious), and the root cause of this panic is the fact that the
ring indexes in xenstore_interface global variable get completely
corrupted, they jump from ~400 to ~30000, which shows that we have a
memory corruption problem in my opinion.
I've been able to reproduce this using a Debian Dom0 (with Linux kernel
2.6.32 and 3.2) with 4vcpus. The procedure is to create a NetBSD DomU,
and try to perform a NetBSD build from sources. I haven't been able to
finish any build inside of a DomU using a Linux Dom0.


From: =?ISO-8859-1?Q?Roger_Pau_Monn=E9?= <>
To: "" <>
Cc: "" <>, ""
Subject: Re: port-xen/47056: Xen NetBSD DomU freeze under Linux Dom0
Date: Wed, 24 Oct 2012 16:59:31 +0200

 This bug was caused by the same issue as port-xen/47056. Revision 1.25
 of src/sys/arch/xen/xen/xengnt.c fixes it.

State-Changed-From-To: open->closed
State-Changed-When: Fri, 30 Nov 2012 09:29:31 +0000
Fixed in src/sys/arch/xen/xen/xengnt.c version 1.25


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