linux-kernel - Re: 2.6.24 says "serial8250: too much work for irq4" a lot.

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Message-ID: <47AB6FD7.1030502@zytor.com>
Date:	Thu, 07 Feb 2008 12:53:43 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Rob Landley <rob@...dley.net>
CC:	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org
Subject: Re: 2.6.24 says "serial8250: too much work for irq4" a lot.

Rob Landley wrote:
> 
> Specifically, qemu isn't paravirtualized, it's fully virtualized.  The same 
> kernel can run on real hardware just fine.  (Sort of the point of the 
> project...)
> 
> I can yank the warning for the kernels I build (or set PASS_LIMIT to 9999999), 
> but I'd rather not carry any more patches than I can avoid...
> 

The right thing to do is to add virtual FIFO exhaustion into the Qemu 
device model.  It really isn't a valid emulation of a UART that it has 
an infinite FIFO behind it that can flood the interrupt handler for an 
arbitrary number of fetches.

I was going to give a technical description of how to do it here, but 
then I realized I might as well just write it up as a patch.  Stay tuned.

	-hpa

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