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Date: Mon, 13 Jun 2016 23:45:10 +0300
From: "Michael S. Tsirkin" <mst@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH 03/10] tests/vhost-user-bridge: workaround
 stale vring base
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To: =?iso-8859-1?Q?Marc-Andr=E9?= Lureau <marcandre.lureau@gmail.com>
Cc: Victor Kaplansky <victork@redhat.com>, Yuanhan Liu <yuanhan.liu@linux.intel.com>, QEMU <qemu-devel@nongnu.org>, Ilya Maximets <i.maximets@samsung.com>, jonshin@cisco.com, Tetsuya Mukawa <mukawa@igel.co.jp>

On Thu, Jun 09, 2016 at 12:25:54PM +0200, Marc-Andr=E9 Lureau wrote:
> Hi
>=20
> On Thu, Jun 9, 2016 at 12:07 PM, Victor Kaplansky <victork@redhat.com> =
wrote:
> > What if set_vring_base is called after set_vring_addr?
> > Maybe it is worth to add the fixup to the set_vring_base as well?
>=20
> It would need to handle conditions like set_vring_base() being called
> while set_vring_addr() is not yet, and thus vq->used isn't set.
>=20
> Imho it's not necessary, since order is currently fixed in
> vhost_virtqueue_start(), but we could specify this in the protocol to
> avoid too much possible states.

I personally think it's better to just get the used idx
from memory before reconnecting.

Will fix old clients automatically.

Whoever wants to support old QEMU, can do this by a work-around
similar to the supplied one. Maybe add code here to make
sure everything is setup - if not it's a new QEMU so
it does not need the work-around.

I think there was a patch like this suggested at some point -
mind digging it up?

> --=20
> Marc-Andr=E9 Lureau