linux-kernel - Re: [PATCH 23/24] hvc_xen: allow dom0_write

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Message-ID: <alpine.DEB.2.02.1208011704000.4645@kaball.uk.xensource.com>
Date:	Wed, 1 Aug 2012 17:04:45 +0100
From:	Stefano Stabellini <stefano.stabellini@...citrix.com>
To:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
CC:	Stefano Stabellini <Stefano.Stabellini@...citrix.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"xen-devel@...ts.xensource.com" <xen-devel@...ts.xensource.com>,
	Ian Campbell <Ian.Campbell@...rix.com>,
	"Tim (Xen.org)" <tim@....org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linaro-dev@...ts.linaro.org" <linaro-dev@...ts.linaro.org>,
	"catalin.marinas@....com" <catalin.marinas@....com>,
	"arnd@...db.de" <arnd@...db.de>
Subject: Re: [PATCH 23/24] hvc_xen: allow dom0_write_console for HVM guests

On Wed, 1 Aug 2012, Konrad Rzeszutek Wilk wrote:
> On Thu, Jul 26, 2012 at 04:34:05PM +0100, Stefano Stabellini wrote:
> > On ARM all guests are HVM guests, including Dom0.
> > Allow dom0_write_console to be called by an HVM domain.
> 
> Um, but xen_hvm_domain() != xen_pv_domain() so won't this return without
> printing anything?

Nope, it would call dom0_write_console that issues a console hypercall.
However I am going to remove this patch and rely on the simple serial
emulator we have in Xen for early_printk stuff

> > 
> > Signed-off-by: Stefano Stabellini <stefano.stabellini@...citrix.com>
> > ---
> >  drivers/tty/hvc/hvc_xen.c |    5 +----
> >  1 files changed, 1 insertions(+), 4 deletions(-)
> > 
> > diff --git a/drivers/tty/hvc/hvc_xen.c b/drivers/tty/hvc/hvc_xen.c
> > index 3c04fb8..949edc2 100644
> > --- a/drivers/tty/hvc/hvc_xen.c
> > +++ b/drivers/tty/hvc/hvc_xen.c
> > @@ -616,12 +616,9 @@ static void xenboot_write_console(struct console *console, const char *string,
> >  	unsigned int linelen, off = 0;
> >  	const char *pos;
> >  
> > -	if (!xen_pv_domain())
> > -		return;
> > -
> >  	dom0_write_console(0, string, len);
> >  
> > -	if (xen_initial_domain())
> > +	if (!xen_pv_domain())
> >  		return;
> >  
> >  	domU_write_console(0, "(early) ", 8);
> > -- 
> > 1.7.2.5
> 
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