Re: [PATCH v2 2/2] xen/arm: Throw messages for unknown FP/SIMD implement ID

[Bertrand Marquis <Bertrand.Marquis@xxxxxxx>]

Hi,

> On 24 Aug 2020, at 04:28, Wei Chen <Wei.Chen@xxxxxxx> wrote:
> 
> Arm ID_AA64PFR0_EL1 register provides two fields to describe CPU
> FP/SIMD implementations. Currently, we exactly know the meaning of
> 0x0, 0x1 and 0xf of these fields. Xen treats value < 8 as FP/SIMD
> features presented. If there is a value 0x2 bumped in the future,
> Xen behaviors for value <= 0x1 can also take effect. But what Xen
> done for value <= 0x1 may not always cover new value 0x2 required.
> We throw these messages to break the silence when Xen detected
> unknown FP/SIMD IDs to notice user to check.
> 
> Signed-off-by: Wei Chen <wei.chen@xxxxxxx>
Reviewed-by: Bertrand Marquis <bertrand.marquis@xxxxxxx>

> ---
> xen/arch/arm/setup.c | 26 ++++++++++++++++++++++++--
> 1 file changed, 24 insertions(+), 2 deletions(-)
> 
> diff --git a/xen/arch/arm/setup.c b/xen/arch/arm/setup.c
> index 7968cee47d..c7802d0e49 100644
> --- a/xen/arch/arm/setup.c
> +++ b/xen/arch/arm/setup.c
> @@ -99,6 +99,28 @@ static const char * __initdata processor_implementers[] = {
>     ['i'] = "Intel Corporation",
> };
> 
> +static const char * __initdata fp_implements[] = {
> +    "Floating-point",
> +    "Floating-point + half-precision floating-point arithmetic",
> +    "Floating-point Unknown ID 0x2",
> +    "Floating-point Unknown ID 0x3",
> +    "Floating-point Unknown ID 0x4",
> +    "Floating-point Unknown ID 0x5",
> +    "Floating-point Unknown ID 0x6",
> +    "Floating-point Unknown ID 0x7",
> +};
> +
> +static const char * __initdata advsimd_implements[] = {
> +    "AdvancedSIMD",
> +    "AdvancedSIMD + half-precision floating-point arithmetic",
> +    "AdvancedSIMD Unknown ID 0x2",
> +    "AdvancedSIMD Unknown ID 0x3",
> +    "AdvancedSIMD Unknown ID 0x4",
> +    "AdvancedSIMD Unknown ID 0x5",
> +    "AdvancedSIMD Unknown ID 0x6",
> +    "AdvancedSIMD Unknown ID 0x7",
> +};
> +
> static void __init processor_id(void)
> {
>     const char *implementer = "Unknown";
> @@ -129,8 +151,8 @@ static void __init processor_id(void)
>            cpu_has_el1_32 ? "64+32" : cpu_has_el1_64 ? "64" : "No",
>            cpu_has_el0_32 ? "64+32" : cpu_has_el0_64 ? "64" : "No");
>     printk("    Extensions:%s%s%s\n",
> -           cpu_has_fp ? " FloatingPoint" : "",
> -           cpu_has_simd ? " AdvancedSIMD" : "",
> +           cpu_has_fp ? fp_implements[boot_cpu_feature64(fp)] : "",
> +           cpu_has_simd ? advsimd_implements[boot_cpu_feature64(simd)] : "",
>            cpu_has_gicv3 ? " GICv3-SysReg" : "");
> 
>     printk("  Debug Features: %016"PRIx64" %016"PRIx64"\n",
> -- 
> 2.17.1
>