linux-kernel - Re: [patch 02/21] Xen-paravirt: Handle a zero-sized VT console

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Date:	Wed, 14 Feb 2007 10:24:47 +0100
From:	Gerd Hoffmann <kraxel@...e.de>
To:	Jeremy Fitzhardinge <jeremy@...p.org>
Cc:	Andi Kleen <ak@....de>, Andrew Morton <akpm@...l.org>,
	linux-kernel@...r.kernel.org, virtualization@...ts.osdl.org,
	xen-devel@...ts.xensource.com, Chris Wright <chrisw@...s-sol.org>,
	Zachary Amsden <zach@...are.com>,
	Alan <alan@...rguk.ukuu.org.uk>
Subject: Re: [patch 02/21] Xen-paravirt: Handle a zero-sized VT console

Jeremy Fitzhardinge wrote:
> If we're running under Xen, then there's no VT console.  This results
> in vc->vc_screenbuf_size == 0, which causes alloc_bootmem to panic.
> Don't bother allocating a vc_screenbuf if its going to be 0 sized.

NAK.

The *real* problem is that the real-mode boot code never ever runs, thus
SCREEN_INFO is not initialized (all zeros), and vgacon doesn't catch
that case.  Instead it thinks it runs on a EGA card with 0 lines and 0
columns.

So better fix vgacon to catch this and switch to the 80x25 dummy console
instead, patch attached.

cheers,

  Gerd


View attachment "vgacon" of type "text/plain" (780 bytes)