linux-kernel - Re: [PATCH 1/5] xen: Enable console tty by default in domU if it's not a dummy

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Message-Id: <20080521172613.18eb24c4.akpm@linux-foundation.org>
Date:	Wed, 21 May 2008 17:26:13 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Markus Armbruster <armbru@...hat.com>
Cc:	linux-kernel@...r.kernel.org,
	virtualization@...ts.linux-foundation.org, jeremy@...p.org,
	xen-devel@...ts.xensource.com,
	linux-fbdev-devel@...ts.sourceforge.net, adaplas@...il.com,
	linux-input@...r.kernel.org, dmitry.torokhov@...il.com,
	mingo@...hat.com, plc@...ell.com
Subject: Re: [PATCH 1/5] xen: Enable console tty by default in domU if it's
 not a dummy

On Wed, 21 May 2008 10:38:50 +0200
Markus Armbruster <armbru@...hat.com> wrote:

> Without console= arguments on the kernel command line, the first
> console to register becomes enabled and the preferred console (the one
> behind /dev/console).  This is normally tty (assuming
> CONFIG_VT_CONSOLE is enabled, which it commonly is).
> 
> This is okay as long tty is a useful console.  But unless we have the
> PV framebuffer, and it is enabled for this domain, tty0 in domU is
> merely a dummy.  In that case, we want the preferred console to be the
> Xen console hvc0, and we want it without having to fiddle with the
> kernel command line.  Commit b8c2d3dfbc117dff26058fbac316b8acfc2cb5f7
> did that for us.
> 
> Since we now have the PV framebuffer, we want to enable and prefer tty
> again, but only when PVFB is enabled.  But even then we still want to
> enable the Xen console as well.
> 
> Problem: when tty registers, we can't yet know whether the PVFB is
> enabled.  By the time we can know (xenstore is up), the console setup
> game is over.
> 
> Solution: enable console tty by default, but keep hvc as the preferred
> console.  Change the preferred console to tty when PVFB probes
> successfully, unless we've been given console kernel parameters.

What a stunningly good changelog - I'd buy the tee-shirt.

Ack on the non-xen bits.
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