Re: [Xen-devel] [PATCH] xen: use hvc console for dom0

[Julien Grall]

Hi,

On 27/02/2018 20:03, Stefano Stabellini wrote:
> On Tue, 27 Feb 2018, Julien Grall wrote:
> > Hi,
> >
> > On 26/02/18 12:32, Juergen Gross wrote:
> > > On 26/02/18 13:06, Andrii Anisov wrote:
> > > > Hello Juergen,
> > > >
> > > >
> > > > On 26.02.18 13:08, Juergen Gross wrote:
> > > > > Today the hvc console is added as a preferred console for pv domUs
> > > > > only. As this requires a boot parameter for getting dom0 messages per
> > > > > default add it for dom0, too.
> > > > >
> > > > > Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
> > > > > ---
> > > > >   Â arch/x86/xen/enlighten_pv.c | 4 +++-
> > > > >   Â 1 file changed, 3 insertions(+), 1 deletion(-)
> > > > >
> > > > > diff --git a/arch/x86/xen/enlighten_pv.c b/arch/x86/xen/enlighten_pv.c
> > > > Is this something x86 specific? Could it be a generic approach?
> > >
> > > In case ARM wants something similar I guess the test for
> > > xen_initial_domain() should be dropped in xen_early_init().
> > I am pretty sure we discussed to remove !xen_initial_domain() for Arm in the
> > past. But I don't remember why the patch was not sent to remove it.
> >
> > Anyway, I guess this should be fine to have hvc as a preferred console for the
> > initial domain as well.
>
> Usually, Dom0 has access to several physical UARTs and/or VGA, making
> this patch less obviously desirable. I think that for Dom0 the best
> behavior would be to add "hvc0" as first console rather than last
> console, so that if the user specified something else, this call won't
> interfere with it.

Well, that's exactly the goal of add_preferred_console. It will use hvc0 
unless specified otherwise by the user on the command line.

Cheers,

--
Julien Grall