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Re: [Qemu-devel] [PATCH v3 15/22] target-arm: A64: Forbid ERET to unimpl


From: Peter Maydell
Subject: Re: [Qemu-devel] [PATCH v3 15/22] target-arm: A64: Forbid ERET to unimplemented ELs
Date: Wed, 21 May 2014 20:06:32 +0100

On 19 May 2014 10:22, Edgar E. Iglesias <address@hidden> wrote:
> From: "Edgar E. Iglesias" <address@hidden>
>
> Check for EL2 support before returning to it.
>
> Reviewed-by: Peter Crosthwaite <address@hidden>
> Signed-off-by: Edgar E. Iglesias <address@hidden>
> ---
>  target-arm/op_helper.c | 11 +++++------
>  1 file changed, 5 insertions(+), 6 deletions(-)
>
> diff --git a/target-arm/op_helper.c b/target-arm/op_helper.c
> index a6eedb2..d89755a 100644
> --- a/target-arm/op_helper.c
> +++ b/target-arm/op_helper.c
> @@ -411,12 +411,11 @@ void HELPER(exception_return)(CPUARMState *env)
>          env->regs[15] = env->elr_el[1] & ~0x1;
>      } else {
>          new_el = extract32(spsr, 2, 2);
> -        if (new_el > cur_el) {
> -            /* Disallow returns to higher ELs than the current one.  */
> -            goto illegal_return;
> -        }

...you just added this if() in the previous patch. Suggest
squashing the two together.

> -        if (new_el > 1) {
> -            /* Return to unimplemented EL */
> +        if (new_el > cur_el
> +            || (new_el == 2 && !arm_feature(env, ARM_FEATURE_EL2))) {
> +            /* Disallow return to an EL which is unimplemented or higher
> +             * than the current one.
> +             */
>              goto illegal_return;
>          }
>          if (extract32(spsr, 1, 1)) {
> --
> 1.8.3.2
>

thanks
-- PMM



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