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From: Pavel Machek <>
To: Alan Cox <>
Cc: Benjamin LaHaise <>,,,
Subject: Re: [PATCH] serial: remove "too much work for irq" printk
Date: Sun, 13 Jan 2008 23:03:27 +0100	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

On Sat 2008-01-12 21:24:57, Alan Cox wrote:
> On Sat, 12 Jan 2008 15:15:43 -0500
> Benjamin LaHaise <> wrote:
> > When using kvm with a serial console, the serial driver will print out 
> > "too much work for irq4" on any heavy activity (ie vi on a file repainting 
> > the terminal).  This message is entirely spurious, as output continues to 
> > work fine.  Remove the message as it corrupts screen output and is far too 
> > easy to trigger.
> NAK. This is a qemu/kvm emulation bug. The real check is there to catched
> jammed IRQs and combined with the IRQ bug handling nowdays does actually
> do the intended job.
> Our serial port code (correctly) interprets a continuous stream of bytes
> at an impossible bit rate as an error. KVM should be emulating to some
> extent at least the timing on serial interfaces or using a virtualised
> interface.

How can you tell apart impossible bit rate from really slow CPU, or
maybe just an SMI storm, or heavy busmaster DMA?

(cesky, pictures)

      parent reply	other threads:[~2008-01-13 22:03 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-01-12 20:15 [PATCH] serial: remove "too much work for irq" printk Benjamin LaHaise
2008-01-12 20:21 ` Christoph Hellwig
2008-01-12 21:24 ` Alan Cox
2008-01-12 21:39   ` H. Peter Anvin
2008-01-12 21:42     ` Alan Cox
2008-01-12 21:58       ` H. Peter Anvin
2008-01-13 22:03   ` Pavel Machek [this message]

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