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Re: [Qemu-devel] [RFC 13/29] vhost+postcopy: Transmit 'listen' to client
From: |
Dr. David Alan Gilbert |
Subject: |
Re: [Qemu-devel] [RFC 13/29] vhost+postcopy: Transmit 'listen' to client |
Date: |
Wed, 26 Jul 2017 18:42:30 +0100 |
User-agent: |
Mutt/1.8.3 (2017-05-23) |
* Maxime Coquelin (address@hidden) wrote:
>
>
> On 06/28/2017 09:00 PM, Dr. David Alan Gilbert (git) wrote:
> > diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
> > index b98fbe4834..1f70f5760f 100644
> > --- a/hw/virtio/vhost-user.c
> > +++ b/hw/virtio/vhost-user.c
> > @@ -67,6 +67,7 @@ typedef enum VhostUserRequest {
> > VHOST_USER_SET_SLAVE_REQ_FD = 21,
> > VHOST_USER_IOTLB_MSG = 22,
> > VHOST_USER_POSTCOPY_ADVISE = 23,
> > + VHOST_USER_POSTCOPY_LISTEN = 24,
> > VHOST_USER_MAX
> > } VhostUserRequest;
> > @@ -771,6 +772,25 @@ static int vhost_user_postcopy_advise(struct vhost_dev
> > *dev, Error **errp)
> > return 0;
> > }
> > +/*
> > + * Called at the switch to postcopy on reception of the 'listen' command.
> > + */
> > +static int vhost_user_postcopy_listen(struct vhost_dev *dev, Error **errp)
> > +{
> > + VhostUserMsg msg = {
> > + .request = VHOST_USER_POSTCOPY_LISTEN,
> > + .flags = VHOST_USER_VERSION,
> > + };
>
> I think it should use REPLY_ACK feature when available for two reasons:
> 1. The backend could reply nack if nregions is already set.
> 2. When leaving vhost_user_postcopy_listen(), the message might likely
> not have been handled yet by the backend.
OK, I can do that. What are the rules on features like that? Can I
just assume that if you've got POSTCOPY then you'll ack for new messages
we add?
The current contrib/libvhost-user code doesn't seem to do acks yet, but
I can add it here quite easily.
Dave
> > + trace_vhost_user_postcopy_listen();
> > + if (vhost_user_write(dev, &msg, NULL, 0) < 0) {
> > + error_setg(errp, "Failed to send postcopy_listen to vhost");
> > + return -1;
> > + }
> > +
> > + return 0;
> > +}
> > +
> > static int vhost_user_postcopy_notifier(NotifierWithReturn *notifier,
> > void *opaque)
> > {
> > @@ -793,6 +813,9 @@ static int
> > vhost_user_postcopy_notifier(NotifierWithReturn *notifier,
> > case POSTCOPY_NOTIFY_INBOUND_ADVISE:
> > return vhost_user_postcopy_advise(dev, pnd->errp);
> > + case POSTCOPY_NOTIFY_INBOUND_LISTEN:
> > + return vhost_user_postcopy_listen(dev, pnd->errp);
> > +
> > default:
> > /* We ignore notifications we don't know */
> > break;
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK