Re: [XEN PATCH] xen/arm: Relax GIC version check

[Julien Grall <julien@xxxxxxx>]

(+ Ian)

Hi Vladimir,

On 20/01/2021 11:26, Vladimir Murzin wrote:
> Supported values are
>
> 0b0000 GIC CPU interface system registers not implemented.
>
> 0b0001 System register interface to versions 3.0 and 4.0 of the GIC
>         CPU interface is supported.
>
> 0b0011 System register interface to version 4.1 of the GIC CPU
>         interface is supported.
>
> 4.1 is still backward compatible with 4.0/3.0, moreover ARM ARM
> guarantees that future versions of the GIC CPU interface retain
> backwards compatible.
>
> Signed-off-by: Vladimir Murzin <vladimir.murzin@xxxxxxx>
Acked-by: Julien Grall <jgrall@xxxxxxxxxx>

@Ian: I would like your put as the RM for 4.15.

Technically, it could be consider as a new "feature" because Xen would 
fail to boot on such HW.
However, I think the change is small enough and doesn't introduce risk 
on existing supported HW.
Therefore, I would like to merge it for 4.15. @Ian does it sounds good 
to you?
> ---
>   xen/include/asm-arm/cpufeature.h | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/xen/include/asm-arm/cpufeature.h b/xen/include/asm-arm/cpufeature.h
> index 13a2739a6..c6e5711b2 100644
> --- a/xen/include/asm-arm/cpufeature.h
> +++ b/xen/include/asm-arm/cpufeature.h
> @@ -17,7 +17,7 @@
>   #define cpu_has_el3_64    (boot_cpu_feature64(el3) >= 1)
>   #define cpu_has_fp        (boot_cpu_feature64(fp) < 8)
>   #define cpu_has_simd      (boot_cpu_feature64(simd) < 8)
> -#define cpu_has_gicv3     (boot_cpu_feature64(gic) == 1)
> +#define cpu_has_gicv3     (boot_cpu_feature64(gic) >= 1)
>   #endif
>   
>   #define cpu_feature32(c, feat)         ((c)->pfr32.feat)
--
Julien Grall