Re: [Qemu-devel] [bisected] VNC server can't get all sent chars correctly

[Gonglei (Arei)]

Hi,

> From: Michael Tokarev [mailto:address@hidden
> Sent: Saturday, August 23, 2014 4:56 PM
> To: qemu-devel
> Cc: Gerd Hoffmann; Gonglei (Arei); address@hidden; Gabriele
> Giacone
> Subject: [bisected] VNC server can't get all sent chars correctly
> 
> There's a bug filed against debian qemu package, there:
> 
>  http://bugs.debian.org/758881
> 
> which says about problems sending keypress events over VNC to
> a qemu guest, -- some keypresses gets lost, at least.
> 
> The bisection between qemu 2.0 and 2.1 leads to this commit:
> 
> commit 2858ab09e6f708e381fc1a1cc87e747a690c4884
> Author: Gonglei <address@hidden>
> Date:   Thu Apr 24 20:06:19 2014 +0800
> 
>     ps2: set ps/2 output buffer size as the same as kernel
> 
>     According to the PS/2 Mouse/Keyboard Protocol, the keyboard outupt
> buffer size
>     is 16 bytes. And the PS2_QUEUE_SIZE 256 was introduced in Qemu from
> the very
>     beginning.
> 
>     When I started a  redhat5.6 32bit guest, meanwhile tapped the keyboard
> as quickly as
>     possible, the screen would show me "i8042.c: No controller found". As a
> result,
>     I couldn't use the keyboard in the VNC client.
> 
>     Previous discussion about the issue in maillist:
> 
> http://thread.gmane.org/gmane.comp.emulators.qemu/43294/focus=47180
> 
>     This patch has been tested on redhat5.6 32-bit/suse11sp3 64-bit guests.
>     More easy meathod to reproduce:
>     1.boot a guest with libvirt.
>     2.connect to VNC client.
>     3.as you see the BIOS, bootloader, Linux booting, run the follow simply
> shell script:
>     for((i=0;i<10000000;i++)) do virsh send-key redhat5.6 KEY_A; done
> 
>     Actual results:
>     dmesg show "i8042.c: No controller found." And the keyboard is out of
> work.
> 
>     Signed-off-by: Gonglei <address@hidden>
>     Reviewed-by: Juan Quintela <address@hidden>
>     Signed-off-by: Gerd Hoffmann <address@hidden>
> 
> 
> So it looks like something else is not right here.  Before this patch,
> it wasn't possible to use keyboard with VNC client with redhat 5 guest.
> Now, it isn't possible to use keyboard with VNC in another scenario which
> worked before (so it is a regression compared with 2.0 version).
> 
> What do we do with this? :)
> 
I tested the same command line with the reported Bug, as below: 

./qemu-system-x86_64 -vnc :10 -enable-kvm -cpu host -m 1024 --kernel \
/home/linux --initrd /home/initrd.gz --append "locale=en_US keymap=us \ 
video=vesa:ywrap,mtrr vga=788"

And the VNC client I tested are TightVNC and RealVNC.

But I could not reproduce this issue.

So, I think maybe vncdotool client once send too many characters
(and ps2 queue length > PS2_QUEUE_SIZE), which leading to some 
characters are discarded by QEMU. More test cases will be useful IMHO.

Best regards,
-Gonglei