Re: [PATCH] target/arm: Restructure has_vfp_d32 test

[Mads Ynddal]

> On 19 Jun 2023, at 16.02, Richard Henderson <richard.henderson@linaro.org> 
> wrote:
> 
> One cannot test for feature aa32_simd_r32 without first
> testing if AArch32 mode is supported at all.  This leads to
> 
> qemu-system-aarch64: ARM CPUs must have both VFP-D32 and Neon or neither
> 
> for Apple M1 cpus.
> 
> We already have a check for ARMv8-A never setting vfp-d32 true,
> so restructure the code so that AArch64 avoids the test entirely.
> 
> Reported-by: Mads Ynddal <mads@ynddal.dk>
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
> target/arm/cpu.c | 28 +++++++++++++++-------------
> 1 file changed, 15 insertions(+), 13 deletions(-)
> 
> diff --git a/target/arm/cpu.c b/target/arm/cpu.c
> index 353fc48567..706dbd37b1 100644
> --- a/target/arm/cpu.c
> +++ b/target/arm/cpu.c
> @@ -1402,25 +1402,27 @@ void arm_cpu_post_init(Object *obj)
>      * KVM does not currently allow us to lie to the guest about its
>      * ID/feature registers, so the guest always sees what the host has.
>      */
> -    if (arm_feature(&cpu->env, ARM_FEATURE_AARCH64)
> -        ? cpu_isar_feature(aa64_fp_simd, cpu)
> -        : cpu_isar_feature(aa32_vfp, cpu)) {
> -        cpu->has_vfp = true;
> -        if (!kvm_enabled()) {
> -            qdev_property_add_static(DEVICE(obj), &arm_cpu_has_vfp_property);
> +    if (arm_feature(&cpu->env, ARM_FEATURE_AARCH64)) {
> +        if (cpu_isar_feature(aa64_fp_simd, cpu)) {
> +            cpu->has_vfp = true;
> +            cpu->has_vfp_d32 = true;
> +            if (tcg_enabled() || qtest_enabled()) {
> +                qdev_property_add_static(DEVICE(obj),
> +                                         &arm_cpu_has_vfp_property);
> +            }
>         }
> -    }
> -
> -    if (cpu->has_vfp && cpu_isar_feature(aa32_simd_r32, cpu)) {
> -        cpu->has_vfp_d32 = true;
> -        if (!kvm_enabled()) {
> +    } else if (cpu_isar_feature(aa32_vfp, cpu)) {
> +        cpu->has_vfp = true;
> +        if (cpu_isar_feature(aa32_simd_r32, cpu)) {
> +            cpu->has_vfp_d32 = true;
>             /*
>              * The permitted values of the SIMDReg bits [3:0] on
>              * Armv8-A are either 0b0000 and 0b0010. On such CPUs,
>              * make sure that has_vfp_d32 can not be set to false.
>              */
> -            if (!(arm_feature(&cpu->env, ARM_FEATURE_V8) &&
> -                  !arm_feature(&cpu->env, ARM_FEATURE_M))) {
> +            if ((tcg_enabled() || qtest_enabled())
> +                && !(arm_feature(&cpu->env, ARM_FEATURE_V8)
> +                     && !arm_feature(&cpu->env, ARM_FEATURE_M))) {
>                 qdev_property_add_static(DEVICE(obj),
>                                          &arm_cpu_has_vfp_d32_property);
>             }
> -- 
> 2.34.1
> 

Perfect! This seems to do it for Apple M1.

Tested-by: Mads Ynddal <m.ynddal@samsung.com>
Reviewed-by: Mads Ynddal <m.ynddal@samsung.com>