Re: [Xen-devel] reboot driver domain, vifX.Y = NO-CARRIER?

[Jason Cooper <xen@xxxxxxxxxxxxxx>]

Hi George,

On Mon, Apr 30, 2018 at 05:38:55PM +0100, George Dunlap wrote:
> On Mon, Apr 30, 2018 at 5:16 PM, Jason Cooper <xen@xxxxxxxxxxxxxx> wrote:
> > Hi Ian,
> >
> > On Mon, Apr 30, 2018 at 04:22:30PM +0100, Ian Jackson wrote:
> >> Wei Liu writes ("Re: [Xen-devel] reboot driver domain, vifX.Y = 
> >> NO-CARRIER?"):
> >> > To implement reuse_domid in a sane way, either the toolstack needs to
> >> > manage all domids and always sets domid when creating domain or the
> >> > hypervisor needs to cooperate -- to have interface to reserve /
> >> > pre-allocate domids.
> >>
> >> I think this is entirely the wrong approach.
> >
> > Whew.  Glad I didn't start hacking yet...
> >
> >> I think the right answer is that this is simply a bug in the
> >> frontends.  frontends should cope if the backend path pointer in the
> >> frontend directory is updated, and should start reading the new
> >> backend instead.
> >
> > Ok, so I'm new to the guts of Xen.  The bug, at a high level, is that
> > "When a driver domain is rebooted (domid changed), previously connected
> > client domUs can't gain network connectivity to/through the driver
> > domain via 'xl network-attach client_domu mac=... bridge=...
> > backend=drv_dom'"
> 
> Hang on -- just to clarify, something like the following doesn't work
> (or wouldn't, you suspect, work)?
> 
> * Start driver domain
> * Start domU A with no network

My setup is different here.  I include the vif = [... backend=...]
declaration in my domain config.

> * xl network-attach A backend=drv_dom

So I don't do this step manually.

> * [do some stuff]
> * xl network-detach A [network devid]
> * Restart driver domain
> * xl network-attach A backend=drv_dom

Otherwise, this is all correct.  Then I get the NO-CARRIER in domU A.

thx,

Jason.

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