Re: [Qemu-devel] [PATCH] hid: Extend the event queue size to 1024

[Alexander Graf <agraf@suse.de>]

On 04/14/2016 05:17 PM, Gerd Hoffmann wrote:
> On Do, 2016-04-14 at 16:25 +0200, Alexander Graf wrote:
>> We can currently buffer up to 16 events in our event queue for input
>> devices. While it sounds like 16 events backlog for everyone should
>> be enough, our automated testing tools (OpenQA) manage to easily
>> type faster than our guests can handle.
> IMO you should fix OpenQA to type slower then.
>
> Real hardware is made for human typing speeds.  qemu emulates real
> hardware.  Typing insane fast is going to cause problems because the
> hardware interfaces are not designed for that.
>
> Note the ps/2 keyboard has only a 16 byte queue too.  Used to be 256
> bytes, but that caused problems because this diverges from real hardware
> (see commit 2858ab09e6f708e381fc1a1cc87e747a690c4884 for all the
> details).
>
> Note that the generic input code has support for slow typing already
> (see qemu_input_event_send_key_delay in ui/input.c).  That queue will
> (a) work for all keyboard devices and (b) isn't visible to the guest, so
> using that might be a reasonable option if you can't put the delay logic
> into OpenQA.  How to you feed the guest with keystrokes?  monitor?  vnc?

It used to type via the monitor, but these days everything goes via vnc.

Vnc already uses qemu_input_event_send_key_delay today, so I'm not sure 
where things fall apart.


Alex