Messages in this thread | | | Date | Thu, 8 Feb 2007 09:41:03 -0500 | From | "Dmitry Torokhov" <> | Subject | Re: [PATCH 9/11] Panic delay fix |
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On 8 Feb 2007 14:33:21 +0100, Andi Kleen <ak@muc.de> wrote: > 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.
There is no throttling, we will switch leds as fast as keyboard controller will allow us (not that I consider it a bad thing).
> > > So the keyboard blinks out of control and acts as if possessed by demons. > > Still sounds weird. >
The problem is that panic blink routine expects to be called with 1ms frequency. If mdelay in kernel/panic.c is changed to noop then i8042 will try to blink as fast as it possibly can.
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