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Re: disappointing upgrade to NetBSD 5.0

On Mon, May 25, 2009 at 10:46:23PM -0700, Dan Engholm wrote:
> To the experts,
> I have been running NetBSD in a Xen user domain on top of NetBSD for
> several years.  I finally decided to upgrade my user domain virtual machine
> from NetBSD 4.0.1 to 5.0.  The installation went without a hitch but
> shortly after booting to the upgraded system, the user domain kernel
> crashed.  The message in the Xen console said:
> panic: Unable to reduce memory reservation
> Begin traceback...
> rx_mcl(5e3a003,1,0,0,0,0,1,c04a1460,1,0) at netbsd:__kernassert+0xb0a90
> End traceback...

Does the traceback end here ?
I've never seen this on a xen2 domU ...

> [...]
> I can't be sure what I am doing to get the problem to occur, but it seems
> to be network related.  Looking around Google, I found one thread in
> port-xen with a similar description but it dead ended with no resolution. 
> (see http://mail-index.netbsd.org/port-xen/2009/01/18/msg004686.html)  I
> thought that since I was still using Xen 2, I should look at this as an
> opportunity to upgrade to Xen 3.  It was a further learning experience but
> I did manage to get Domain0 up and running and also got my user domain
> created and booting.  But, before it finished its rc script, it died:
> Setting sysctl variables:
> vfs.generic.usermount: 0 -> 1
> kern.no_sa_support: 0 -> 1
> ddb.onpanic: 1 -> 0
> Starting network.
> Hostname: xxxxx.xxxxxxx.org
> IPv6 mode: host
> Configuring network interfaces: xennet0.
> Adding interface aliases:.
> add net default: gateway yyyyyy
> Building databases:panic: buf mem pool index 7
> Begin traceback...
> uvm_fault(0xc9d58b98, 0, 1) -> 0xe

Null pointer dereference

> fatal page fault in supervisor mode
> trap type 6 code 0 eip c0396531 cs 9 eflags 10246 cr2 0 ilevel 0
> panic: trap
> Faulted in mid-traceback; aborting...

the stack is trashed. Maybe it's running out of stack space ?
How much RAM did you allocate to this domU ?

> [...]
> Since the upgrade, my user domain no longer boots without intervention.  It
> does not figure out on its own where the root partition is so I have to
> manually enter "xbd0a" from the Xen console.  The configuration file has
> 'root = "/dev/xbd0a"' in it as it has since I started using Xen.  This is
> true regardless of which version of Xen I use.

root = "xbd0"

> Also, I got burned by Xen telling me that the "nics" configuration option
> is obsolete.  The man page says that it's still valid and that its default
> value is 1.  If I don't have a "nics = 1" line in my configuration file, no
> NICs are created and the creation fails because it can't configure the
> network.  What gives?

Do you have a vif array in your domU configuration ? something like
vif = [ 'mac=00:16:3e:00:12:00, bridge=bridge0']

I don't have a nics= line in my xen3 domU configs, the nic number is
fixed by the size of the vif array.

Manuel Bouyer <bouyer%antioche.eu.org@localhost>
     NetBSD: 26 ans d'experience feront toujours la difference

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