linux-kernel - Re: [PATCH 9/11] Panic delay fix

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Message-ID: <20070208133321.GA36397@muc.de>
Date:	Thu, 8 Feb 2007 14:33:21 +0100
From:	Andi Kleen <ak@....de>
To:	Zachary Amsden <zach@...are.com>
Cc:	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...l.org>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Jeremy Fitzhardinge <jeremy@...p.org>,
	Chris Wright <chrisw@...s-sol.org>
Subject: Re: [PATCH 9/11] Panic delay fix

On Thu, Feb 08, 2007 at 01:08:14AM -0800, Zachary Amsden wrote:
> Andi Kleen wrote:
> >On Wed, Feb 07, 2007 at 02:31:57PM -0800, Zachary Amsden wrote:
> >  
> >>Dmitry Torokhov wrote:
> >>    
> >>>I am confused - does i8042 talk to a virtual or real hardware here? In
> >>>any case I think you need to fix kernel/panic.c to have proper
> >>>(m)delay, not mess with i8042.
> >>>      
> >>I think I need to fix both of them actually.  This is virtual hardware, 
> >>but when you grab focus on a VM, the virtual hardware gets reflected to 
> >>the actual physical keyboard.  Driving physical hardware that fast is bad.
> >>    
> >
> >???
> >
> >Surely the physical keyboard is always handled by the host kernel? 
> >I hope you're not saying it's trying to access the io ports directly?
> >  
> 
> No, not that.  But the virtual keyboard I/O gets processed and converted 
> to physical keyboard I/O when a keyboard is attached to a VM.  The 

You mean the commands to change the keyboard LEDs?

> result is that the virtual keyboard spinning out of control causes the 
> physical keyboard to receive the same commands, far too rapidly.

Hmm i would expect the host kernel keyboard driver to throttle these.
I'm pretty sure the Linux one does the necessary mdelays at least.

> So the keyboard blinks out of control and acts as if possessed by demons.

Still sounds weird.

-Andi
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