On Thu, May 10, 2007 at 08:35:17PM +0300, Martti Kuparinen wrote:
> Re: Number of interfaces in Xen 3
> 
> So I'm running NetBSD 4.0_BETA2 and I tried to add 16 interfaces to my domU 
> but it crashed. It works with 7 interfaces but more than 7 caused the domU 
> to crash like this.
> 
> Martti
> 
> 
> xenbus0 at hypervisor0: Xen Virtual Bus Interface
> xencons0 at hypervisor0: Xen Virtual Console Driver
> xencons0: console major 143, unit 0
> xencons0: using event channel 2
> npx0 at hypervisor0: using exception 16
> Xen clock: using event channel 4
> Kernelized RAIDframe activated
> md0: internal 5000 KB image area
> xenbus0: using event channel 1
> [...]
> xennet15 at xenbus0 id 15: Xen Virtual Network Interface
> xennet15: MAC address 00:16:3e:00:00:10
> xbd0 at xenbus0 id 1: Xen Virtual Block Device Interface
> uvm_fault(0xc0730140, 0xe0750000, 2) -> 0xe
> kernel: supervisor trap page fault, code=0
> Stopped in pid 3.1 (xenwatch) at        netbsd:xengnt_free_entry+0x2b:  orl 
> %
> edx,netbsd:gnt_entries_bitmask(,%ebx,4)
> db>

Hum, I'm not sure I tried that many interfaces on a xen3 system.
Does your kernel have DIAGNOSTIC  (it's in XEN2_DOMU and XEN3_DOMU by
default, but not INSTALL_XEN*) ?

Looks like we're running out of grant entries. I don't have an immediate
solution for this; other than maybe hacking if_xennet_xenbus.c to
use less receive buffer (in xennet_xenbus_attach(), change the for(;;) loop
to use something less than NET_RX_RING_SIZE - it may work but I've not
tested it :)

Xen 3.0.4 is still limited to 4 grant pages per domain; -unstable has
a much larger limit but I don't know if it'll be in 3.0.5.

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