From mboxrd@z Thu Jan  1 00:00:00 1970
From: Jeremy Fitzhardinge <jeremy@goop.org>
Subject: Re: pv_ops dom0 and kernel console output problem
Date: Wed, 31 Dec 2008 09:44:52 +1100
Message-ID: <495AA464.6080501@goop.org>
References: <20081226115145.GP15052@edu.joroinen.fi>
	<20081229165130.GR15052@edu.joroinen.fi>
	<1e16a9ed0812290855j59e80e3ei37cb4d2ea75b8ae5@mail.gmail.com>
	<20081229170238.GS15052@edu.joroinen.fi>
	<1e16a9ed0812290915x6c72a28fhc0e7ffcdbc456f60@mail.gmail.com>
	<20081229173041.GU15052@edu.joroinen.fi>
	<1e16a9ed0812290941i2534abfcsbcc67293b8da1608@mail.gmail.com>
	<4959FFBA.4080501@goop.org>
	<20081230130703.GZ15052@edu.joroinen.fi>
	<20081230132036.GA15052@edu.joroinen.fi>
	<20081230150331.GF15052@edu.joroinen.fi>
Mime-Version: 1.0
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: quoted-printable
Return-path: <xen-devel-bounces@lists.xensource.com>
In-Reply-To: <20081230150331.GF15052@edu.joroinen.fi>
List-Unsubscribe: <http://lists.xensource.com/mailman/listinfo/xen-devel>,
	<mailto:xen-devel-request@lists.xensource.com?subject=unsubscribe>
List-Post: <mailto:xen-devel@lists.xensource.com>
List-Help: <mailto:xen-devel-request@lists.xensource.com?subject=help>
List-Subscribe: <http://lists.xensource.com/mailman/listinfo/xen-devel>,
	<mailto:xen-devel-request@lists.xensource.com?subject=subscribe>
Sender: xen-devel-bounces@lists.xensource.com
Errors-To: xen-devel-bounces@lists.xensource.com
To: =?ISO-8859-1?Q?Pasi_K=E4rkk=E4inen?= <pasik@iki.fi>
Cc: deshantm@gmail.com, xen-devel@lists.xensource.com, Andrew Lyon <andrew.lyon@gmail.com>
List-Id: xen-devel@lists.xenproject.org

Pasi K=E4rkk=E4inen wrote:
> Reading pv_ops wiki page I noticed this:
>
> "If the domain crashes very early, before any output appears on the con=
sole,
> then booting with: "earlyprintk=3Dxen" should provide some useful infor=
mation.
> If you are running a debug build of Xen hypervisor (set "debug =3D y" i=
n
> Config.mk in the Xen source tree), then you should get crash dumps on t=
he
> Xen console. You can view those with "xm dmesg"."
>
> So I guess earlyprintk=3Dxen is only useful if you're running debug bui=
ld of
> Xen hypervisor.. ?

earlyprintk=3Dxen has the effect of directing the kernel's console output=
=20
via the console output hypercall.  domU kernel's are not generally=20
allowed to do this, but it is when you compile Xen in debug mode.  dom0,=20
however, uses the Xen console in the normal case, so it doesn't need a=20
debug Xen build.  But when Xen switches its console output to serial the=20
kernel's output goes with it, so if you want it to appear on VGA you=20
need to use the VGA console output (make sure your kernel has all the VT=20
console options enabled).

    J