linux-kernel - Re: [PATCH v2 2/3] hvc_xen: fix xenboot for DomUs

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Date:	Fri, 26 Feb 2016 15:39:41 +0000
From:	Stefano Stabellini <stefano.stabellini@...citrix.com>
To:	Boris Ostrovsky <boris.ostrovsky@...cle.com>
CC:	Stefano Stabellini <stefano.stabellini@...citrix.com>,
	<xen-devel@...ts.xensource.com>, <linux-kernel@...r.kernel.org>,
	<david.vrabel@...rix.com>, <konrad.wilk@...cle.com>
Subject: Re: [PATCH v2 2/3] hvc_xen: fix xenboot for DomUs

On Thu, 25 Feb 2016, Boris Ostrovsky wrote:
> On 02/25/2016 07:10 AM, Stefano Stabellini wrote:
> > The xenboot early console has been partially broken for DomU for a long
> > time: the output would only go to the hypervisor via hypercall
> > (HYPERVISOR_console_io), while it wouldn't actually go to the DomU
> > console. The reason is that domU_write_console would return early as no
> > xencons structs are configured for it.
> > 
> > Add an appropriate xencons struct for xenboot from the xenboot setup
> > callback.
> > 
> > Signed-off-by: Stefano Stabellini <stefano.stabellini@...citrix.com>
> > 
> > ---
> > Changes in v2:
> > - add return to xenboot_setup_console
> > ---
> >   drivers/tty/hvc/hvc_xen.c |   32 ++++++++++++++++++++++++++------
> >   1 file changed, 26 insertions(+), 6 deletions(-)
> > 
> > diff --git a/drivers/tty/hvc/hvc_xen.c b/drivers/tty/hvc/hvc_xen.c
> > index 68b8ec8..bf787aa 100644
> > --- a/drivers/tty/hvc/hvc_xen.c
> > +++ b/drivers/tty/hvc/hvc_xen.c
> > @@ -246,6 +246,18 @@ err:
> >   	return -ENODEV;
> >   }
> >   +static int xen_early_pv_console_init(struct xencons_info *info, int
> > vtermno)
> 
> Nit: not sure whether "early" is the right word to use here: when called from
> xen_pv_console_init() it's not really on the early path.

What about xencons_info_pv_init?


> Other than that:
> Reviewed-by: Boris Ostrovsky <boris.ostrovsky@...cle.com>

Thanks!


> > +{
> > +	info->evtchn = xen_start_info->console.domU.evtchn;
> > +	/* GFN == MFN for PV guest */
> > +	info->intf = gfn_to_virt(xen_start_info->console.domU.mfn);
> > +	info->vtermno = vtermno;
> > +
> > +	list_add_tail(&info->list, &xenconsoles);
> > +
> > +	return 0;
> > +}
> > +
> >   static int xen_pv_console_init(void)
> >   {
> >   	struct xencons_info *info;
> > @@ -265,13 +277,8 @@ static int xen_pv_console_init(void)
> >   		/* already configured */
> >   		return 0;
> >   	}
> > -	info->evtchn = xen_start_info->console.domU.evtchn;
> > -	/* GFN == MFN for PV guest */
> > -	info->intf = gfn_to_virt(xen_start_info->console.domU.mfn);
> > -	info->vtermno = HVC_COOKIE;
> > -
> >   	spin_lock(&xencons_lock);
> > -	list_add_tail(&info->list, &xenconsoles);
> > +	xen_early_pv_console_init(info, HVC_COOKIE);
> >   	spin_unlock(&xencons_lock);
> >     	return 0;
> > @@ -599,6 +606,18 @@ static int xen_cons_init(void)
> >   console_initcall(xen_cons_init);
> >     #ifdef CONFIG_EARLY_PRINTK
> > +static int __init xenboot_setup_console(struct console *console, char
> > *string)
> > +{
> > +	static struct xencons_info xenboot;
> > +
> > +	if (xen_initial_domain())
> > +		return 0;
> > +	if (!xen_pv_domain())
> > +		return -ENODEV;
> > +
> > +	return xen_early_pv_console_init(&xenboot, 0);
> > +}
> > +
> >   static void xenboot_write_console(struct console *console, const char
> > *string,
> >   				  unsigned len)
> >   {
> > @@ -629,6 +648,7 @@ static void xenboot_write_console(struct console
> > *console, const char *string,
> >   struct console xenboot_console = {
> >   	.name		= "xenboot",
> >   	.write		= xenboot_write_console,
> > +	.setup		= xenboot_setup_console,
> >   	.flags		= CON_PRINTBUFFER | CON_BOOT | CON_ANYTIME,
> >   	.index		= -1,
> >   };
>