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

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Date:	Thu, 25 Feb 2016 10:04:52 -0500
From:	Boris Ostrovsky <boris.ostrovsky@...cle.com>
To:	Stefano Stabellini <stefano.stabellini@...citrix.com>,
	xen-devel@...ts.xensource.com
Cc:	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 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.

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

> +{
> +	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,
>   };