Re: [PATCH 3/3] firmware/shim: UNSUPPORTED=n

From: "Roger Pau Monné" <roger.pau@citrix.com>
To: Jan Beulich <jbeulich@suse.com>
Cc: "xen-devel@lists.xenproject.org" <xen-devel@lists.xenproject.org>,
	"Andrew Cooper" <andrew.cooper3@citrix.com>, Wei Liu <wl@xen.org>,
	Ian Jackson <iwj@xenproject.org>,
	Stefano Stabellini <sstabellini@kernel.org>,
	"George Dunlap" <george.dunlap@citrix.com>,
	Dario Faggioli <dfaggioli@suse.com>
Subject: Re: [PATCH 3/3] firmware/shim: UNSUPPORTED=n
Date: Tue, 25 May 2021 16:39:01 +0200	[thread overview]
Message-ID: <YK0MBTWXYJmihvUn@Air-de-Roger> (raw)
In-Reply-To: <dbfa9126-6809-64cf-5bd5-01b402616f11@suse.com>

On Fri, Apr 30, 2021 at 04:45:03PM +0200, Jan Beulich wrote:
> We shouldn't default to include any unsupported code in the shim. Mark
> the setting as off, replacing the ARGO specification. This points out
> anomalies with the scheduler configuration: Unsupported schedulers
> better don't default to Y in release builds (like is already the case
> for ARINC653). Without these adjustments, the shim would suddenly build
> with RTDS as its default scheduler.
> 
> Signed-off-by: Jan Beulich <jbeulich@suse.com>

Acked-by: Roger Pau Monné <roger.pau@citrix.com>

> ----
> I'm certainly open to consider alterations on the sched/Kconfig
> adjustments, but _something_ needs to be done there. In particular I'm
> puzzled to find the NULL scheduler marked unsupported. Clearly with
> the shim defaulting to it, it must be supported at least there.

Indeed, I think we should mark NULL as supported for the shim usage
(which is very specific anyway, because it manages a single domain).

> --- a/xen/arch/x86/configs/pvshim_defconfig
> +++ b/xen/arch/x86/configs/pvshim_defconfig
> @@ -15,7 +15,7 @@ CONFIG_SCHED_NULL=y
>  # CONFIG_KEXEC is not set
>  # CONFIG_XENOPROF is not set
>  # CONFIG_XSM is not set
> -# CONFIG_ARGO is not set
> +# CONFIG_UNSUPPORTED is not set
>  # CONFIG_SCHED_CREDIT is not set
>  # CONFIG_SCHED_CREDIT2 is not set
>  # CONFIG_SCHED_RTDS is not set
> --- a/xen/common/sched/Kconfig
> +++ b/xen/common/sched/Kconfig
> @@ -16,7 +16,7 @@ config SCHED_CREDIT2
>  
>  config SCHED_RTDS
>  	bool "RTDS scheduler support (UNSUPPORTED)" if UNSUPPORTED
> -	default y
> +	default DEBUG

I would also be fine with leaving the default as 'n' for unsupported
features.

>  	---help---
>  	  The RTDS scheduler is a soft and firm real-time scheduler for
>  	  multicore, targeted for embedded, automotive, graphics and gaming
> @@ -31,7 +31,7 @@ config SCHED_ARINC653
>  
>  config SCHED_NULL
>  	bool "Null scheduler support (UNSUPPORTED)" if UNSUPPORTED
> -	default y
> +	default PV_SHIM || DEBUG

Do we need the pvshim_defconfig to set CONFIG_SCHED_NULL=y after this?

Thanks, Roger.