Re: [Qemu-arm] [PATCH] target-arm: Don't report presence of EL2 if it doesn't exist

[Sergey Fedorov <serge.fdrv@gmail.com>]

On 02.02.2016 21:20, Peter Maydell wrote:
> We already modify the processor feature bits to not report EL3
> support to the guest if EL3 isn't enabled for the CPU we're emulating.
> Add similar support for not reporting EL2 unless it is enabled.
> This is necessary because real world guest code running at EL3
> (trusted firmware or bootloaders) will query the ID registers to
> determine whether it should start a guest Linux kernel in EL2 or EL3.
>
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

Reviewed-by: Sergey Fedorov <serge.fdrv@gmail.com>

> ---
> When full EL2 arrives and we have the CPU property for it then
> this will expand a bit to look like the 'if (!cpu->has_el3)'
> condition just above it.
>
>  target-arm/cpu.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
>
> diff --git a/target-arm/cpu.c b/target-arm/cpu.c
> index 6c34476..0cc075d 100644
> --- a/target-arm/cpu.c
> +++ b/target-arm/cpu.c
> @@ -650,6 +650,15 @@ static void arm_cpu_realizefn(DeviceState *dev, Error **errp)
>          cpu->id_aa64pfr0 &= ~0xf000;
>      }
>  
> +    if (!arm_feature(env, ARM_FEATURE_EL2)) {
> +        /* Disable the hypervisor feature bits in the processor feature
> +         * registers if we don't have EL2. These are id_pfr1[15:12] and
> +         * id_aa64pfr0_el1[11:8].
> +         */
> +        cpu->id_aa64pfr0 &= ~0xf00;
> +        cpu->id_pfr1 &= ~0xf000;
> +    }
> +
>      if (!cpu->has_mpu) {
>          unset_feature(env, ARM_FEATURE_MPU);
>      }