Re: [Qemu-devel] [RFC v2 1/2] docs: vhost-user: add in-band kick/call messages

[Johannes Berg]

On Thu, 2019-09-12 at 09:09 +0100, Dr. David Alan Gilbert wrote:
> 
> You're actually using the same trick of using
> REPLY_ACK/need_reply  to make it synchronous that set_mem_table does;

I don't think it's really the same - though arguably I could have
spec'ed the inband signal to *require* an ACK. The way I did it relies
on the REPLY_ACK extension.

SET_MEM_TABLE actually specifies a 3-way handshake, qemu->device,
device->qemu, qemu->device.

> that makes sense - but then new calls are getting it to actually process
> some data/commands on the ring itself?

No, the calls (or more specifically the REPLY_ACK to them) are really in
simulation to only acknowledge the interrupt (kick/call) signal has been
received and accounted for on the simulation calendar, the actual
processing happens when the calendar event is scheduled.

johannes