Re: [PATCH v2] target/arm: ensure we use current exception state after SCR update

[Richard Henderson <richard.henderson@linaro.org>]

On 12/12/19 3:47 AM, Alex Bennée wrote:
> A write to the SCR can change the effective EL by droppping the system
> from secure to non-secure mode. However if we use a cached current_el
> from before the change we'll rebuild the flags incorrectly. To fix
> this we introduce the ARM_CP_NEWEL CP flag to indicate the new EL
> should be used when recomputing the flags.
> 
> Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
> Tested-by: Philippe Mathieu-Daudé <philmd@redhat.com>
> Cc: Richard Henderson <richard.henderson@linaro.org>
> Message-Id: <20191209143723.6368-1-alex.bennee@linaro.org>
> 
> ---
> v2
>   - don't override a ARM_CP_SPECIAL, use a new flag
> ---
>  target/arm/cpu.h       |  8 ++++++--
>  target/arm/helper.h    |  1 +
>  target/arm/helper.c    | 14 +++++++++++++-
>  target/arm/translate.c |  6 +++++-
>  4 files changed, 25 insertions(+), 4 deletions(-)

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>


>              if (arm_dc_feature(s, ARM_FEATURE_M)) {
>                  gen_helper_rebuild_hflags_m32(cpu_env, tcg_el);
>              } else {
> -                gen_helper_rebuild_hflags_a32(cpu_env, tcg_el);
> +                if (ri->type & ARM_CP_NEWEL) {
> +                    gen_helper_rebuild_hflags_a32_newel(cpu_env);
> +                } else {
> +                    gen_helper_rebuild_hflags_a32(cpu_env, tcg_el);
> +                }
>              }

If you tweak this again, an else if would be appropriate.


r~