Re: [Xen-users] domU with two eth but only one is active

[Ian Campbell <ian.campbell@xxxxxxxxxx>]

On Sat, 2015-07-18 at 11:07 +0200, SZABO Zsolt wrote:
> On Sat, 18 Jul 2015, Ian Campbell wrote:
> 
> > On Sat, 2015-07-18 at 00:56 +0200, SZABO Zsolt wrote:
> > [...]
> >> What can be the problem?
> >
> > Nothing in the configuration you describe stands out to me as being
> > wrong.
> >
> > Do you have eth1 configured within the guest? What does the in-guest
> > config and state look like?
> 
> Originally, both eth0 and eth1 in domU was configured by dhcp
> but now it only works for eth0, thus, I configure eth1 static:
> 
> auto eth0
> iface eth0 inet dhcp
> 
> auto eth1
> iface eth1 inet static
>          address 192.168.3.2
>          network 255.255.255.0
>          broadcast 192.168.3.255
> 
> I have also checked dmesg in the guest:
> # dmesg |grep -i net
> [    0.033297] Initializing cgroup subsys net_cls
> [    0.033330] Initializing cgroup subsys net_prio
> [    0.118117] NET: Registered protocol family 16
> [    0.208776] NET: Registered protocol family 2
> [    0.212141] NET: Registered protocol family 1
> [    0.301223] audit: initializing netlink subsys (disabled)
> [    1.376536] NET: Registered protocol family 10
> [    1.377181] NET: Registered protocol family 17
> [    1.472973] xen_netfront: Initialising Xen virtual ethernet driver
> [    1.601085] xen_netfront: can't alloc rx grant refs

This is strange, and I would bet related to your problem.

> [    1.601105] net eth1: only created 16 queues

and this is maybe related too.

I'm afraid I've run out of time to investigate for the weekend, but I'll
see what I can figure out next week.

In the meantime off the top of my head in addition to googling those
messages it might be worth investigating options for extending the
number of grant entries which a guest is allowed to use and perhaps
whether multiqueue networking can be disabled (therefore reducing the
need for grant entries).

> [    9.095908] FS-Cache: Netfs 'nfs' registered for caching
> 
> 
> > Did you upgrade the guest too or just dom0?
> 
> I have also upgraded the guest to jessie...
> 
> > Some versions of xl were fussy about spaces within the vif descriptions
> > (like the one before the "bridge=" in yours). Since your eth0 works I
> > doubt this is the issue you are seeing, but I suppose it is worth
> > removing them just in case.
> 
> I have tried, nothing improved. :-(
> [...]
> 
> Ok, I have another linux domU but with wheezy. Originally, only eth0 was 
> configured, but now I have also tried to add eth1 similarly as to
> the jessie domU and it works...

Good to know.

> The dmesg of this domU is shorter:
> # dmesg |grep net
> [    0.004000] Initializing cgroup subsys net_cls
> [    0.004000] Initializing cgroup subsys net_prio
> [    0.134434] microcode: Microcode Update Driver: v2.00 
> <tigran@xxxxxxxxxxxxxxxxxxxx>, Peter Oruba
> [    0.134838] audit: initializing netlink subsys (disabled)
> [    1.340978] xen_netfront: Initialising Xen virtual ethernet driver
> 
> Maybe the jessie upgrade missed some feature of the later upgraded dom0?
> Or it is about some kind of other conflict...?

I think a new feature of the Jessie kernel(s) is running up against some
resource limit when two NICs are used.

Ian.


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