On Mon, Jul 25, 2016 at 04:43:43PM +0200, Roger Pau Monné wrote:
> Adding Wei to the Cc list since he added the multiqueue functionality.
> 
> On Mon, Jul 25, 2016 at 02:59:02PM +0100, Karl Pielorz wrote:
> > 
> > --On 22 July 2016 13:55 +0200 Roger Pau Monné <roger....@citrix.com> wrote:
> > 
> > > In my environment I've migrated a FreeBSD VM with 2 cpus for > 100
> > > consecutive times without seeing any issues (or freezes), although this
> > > was  with OSS Xen and without xe-guest-utilities. Karl, have you tested
> > > HEAD  recently?
> > 
> > Ok, I have tested this with r303286 - it seems to work OK. The hosts gain no
> > time that I can see while migrating, and NTP stays happy.
> > 
> > I did get a panic after about 40 migrations - but that seems to be some
> > network issue or something...
> > 
> >   ('panic called with 0 available queues / dbt_trace_self_wrapper / vpanic /
> > kassert_panic / xn_txq_mq_start / ether_output / udp_send / sosend_dgram /
> > kern_sendit / sendit / sys_sendto / amd64_syscall / Xfast_syscall)
> 
> I haven't been able to reproduce this, but I think it's possible that if you 
> migrate an active netfront xn_txq_mq_start might be called during the 
> migration, just in the middle of the setup_device reconfiguation (while 
> info->num_queues is 0).
> 
> Wei, I think netif_disconnect_backend should set IFF_DRV_OACTIVE in order to 
> notify the net subsystem that the queues are full, so no further calls to 
> xn_txq_mq_start happen until the resume has finished, do you agree?
> 

Perhaps clear IFF_DRV_RUNNING and only set it when the device is ready?
Looking at the manpage is seems more appropriate to me semantically.

Wei.

> Roger.
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