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Date: Wed, 25 Nov 2009 10:03:01 +0100
From: Carsten Otte <carsteno@de.ibm.com>
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Subject: Re: [Qemu-devel] [PATCH 10/13] Implement early printk in
	virtio-console
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To: Anthony Liguori <anthony@codemonkey.ws>
Cc: Carsten Otte <cotte@de.ibm.com>, Alexander Graf <agraf@suse.de>, Aurelien Jarno <aurelien@aurel32.net>, qemu-devel@nongnu.org

Anthony Liguori wrote:
> What is this used for?
On x86 the kernel uses bios output for early prints. We don't have bios 
and do therefore need to bring up a console device as early as possible 
so that we can see kernel panics during I/O subsystem detection/startup. 
All s390 console devices do support this function (3215/3270 and ASCII 
console), and it is used only up to the point when the kernel has its 
console subsystem ready to run.