Re: [Qemu-devel] [PATCH] chardev/char-socket: add POLLHUP handler

["Daniel P. Berrange" <berrange@redhat.com>]

On Tue, Jan 16, 2018 at 06:56:20PM +0100, Marc-André Lureau wrote:
> Hi
> 
> On Wed, Jan 10, 2018 at 2:18 PM, Klim Kireev <klim.kireev@virtuozzo.com> wrote:
> > The following behavior was observed for QEMU configured by libvirt
> > to use guest agent as usual for the guests without virtio-serial
> > driver (Windows or the guest remaining in BIOS stage).
> >
> > In QEMU on first connect to listen character device socket
> > the listen socket is removed from poll just after the accept().
> > virtio_serial_guest_ready() returns 0 and the descriptor
> > of the connected Unix socket is removed from poll and it will
> > not be present in poll() until the guest will initialize the driver
> > and change the state of the serial to "guest connected".
> >
> > In libvirt connect() to guest agent is performed on restart and
> > is run under VM state lock. Connect() is blocking and can
> > wait forever.
> > In this case libvirt can not perform ANY operation on that VM.
> 
> Adding Daniel in CC for comments about libvirt behaviour.

This is a libvirt bug - libvirt should put a finite timeout on connecting
to the guest agent socket to avoid this.

Regards,
Daniel
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