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From: "Dmitry Torokhov" <dmitry.torokhov@gmail.com>
To: "Andi Kleen" <ak@muc.de>
Cc: "Zachary Amsden" <zach@vmware.com>,
	"Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>,
	"Andrew Morton" <akpm@osdl.org>,
	"Rusty Russell" <rusty@rustcorp.com.au>,
	"Jeremy Fitzhardinge" <jeremy@goop.org>,
	"Chris Wright" <chrisw@sous-sol.org>
Subject: Re: [PATCH 9/11] Panic delay fix
Date: Thu, 8 Feb 2007 09:41:03 -0500	[thread overview]
Message-ID: <d120d5000702080641p515b0226v27f208d0e685b898@mail.gmail.com> (raw)
In-Reply-To: <20070208133321.GA36397@muc.de>

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.

-- 
Dmitry

  reply	other threads:[~2007-02-08 14:41 UTC|newest]

Thread overview: 31+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-02-06  3:53 Zachary Amsden
2007-02-06 12:27 ` Andi Kleen
2007-02-06 21:59   ` Zachary Amsden
2007-02-07 12:35     ` Pavel Machek
2007-02-07 20:36       ` Rusty Russell
2007-02-07 22:23         ` Zachary Amsden
2007-02-08 14:43         ` Dmitry Torokhov
2007-02-08 21:26           ` Zachary Amsden
2007-02-08 21:37             ` Dmitry Torokhov
2007-02-14 12:26         ` Pavel Machek
2007-02-14 19:47           ` Zachary Amsden
2007-02-14 12:52         ` Alan
2007-02-14 20:04           ` Zachary Amsden
2007-02-14 21:34             ` Alan
2007-02-14 21:53               ` Zachary Amsden
2007-02-15  0:33                 ` Alan
2007-02-15 10:17             ` Pavel Machek
2007-02-15 23:42               ` Zachary Amsden
2007-02-15 23:49                 ` Pavel Machek
2007-02-15 23:50                 ` Jeremy Fitzhardinge
2007-02-16  3:22                 ` Rusty Russell
2007-02-07 14:58     ` Dmitry Torokhov
2007-02-07 22:31       ` Zachary Amsden
2007-02-08  8:24         ` Andi Kleen
2007-02-08  9:08           ` Zachary Amsden
2007-02-08 13:33             ` Andi Kleen
2007-02-08 14:41               ` Dmitry Torokhov [this message]
2007-02-14 12:49             ` Alan
2007-02-14 22:51 ` Rusty Russell
2007-02-15  0:28   ` Alan
2007-02-15 13:35   ` Dmitry Torokhov

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