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Re: [Qemu-devel] [PATCH RFC] ps2: set the keybord output buffer size as

From: Gonglei (Arei)
Subject: Re: [Qemu-devel] [PATCH RFC] ps2: set the keybord output buffer size as the same as kernel
Date: Wed, 23 Apr 2014 14:26:31 +0000

>   Hi,
> > > Completely separate question:  Have you figured what the root cause for
> > > the bug is?
> >
> > > While wading through the code I've figured the queue size
> > > isn't (directly) exposed to the guest.
> > The process correspond with the above linux kernel code, i8042_flush(void).
> So linux tries to flush the buffer, then is confused in case it can read
> more than 16 bytes (which is the buffer size of real hardware) without
> seeing the status register signaling that the buffer is empty.  So the
> qemu internal buffer size is indirectly visible to the guest.

> Hmm.
> We could try sending the data to the guest in chunks, i.e. signal
> "buffer empty", then set up a (short) timer when we'll go make it appear
> to the guest as if new data arrived (which in reality just comes from
> out large buffer).
> Not that easy to do, as we should better avoid splitting messages in the
> middle.
> > > but for mouse events we
> > > probably want keep some more space to buffer events ...
> > >
> > Maybe you are right, and I worry about it too. At present,
> > but I haven't feel uncomfortable by VNC client then before.
> Do you have a usb-tablet attached, for more comfortable absolute
> coordinates?  If so, then the ps/2 mouse will not be used to deliver
> events to the guest.
I have tested the two situation, both using usb-tablet and not using usb-tablet 

> And as this is a pretty common setup we maybe should not worry too much
> about the ps/2 mouse queue depth ...
> cheers,
>   Gerd

Best regards,

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