Re: [PATCH for-8.0] target/s390x/tcg/mem_helper: Test the right bits in psw_key_valid()

[Nina Schoetterl-Glausch <nsg@linux.ibm.com>]

On Mon, 2022-12-05 at 15:20 +0100, Thomas Huth wrote:
> The PSW key mask is a 16 bit field, and the psw_key variable is
> in the range from 0 to 15, so it does not make sense to use
> "0x80 >> psw_key" for testing the bits here. We should use 0x8000
> instead.
> 
> Signed-off-by: Thomas Huth <thuth@redhat.com>

Reviewed-by: Nina Schoetterl-Glausch <nsg@linux.ibm.com>

> ---
>  Found by code inspection (Linux likely does not use these PSW key masks
>  yet, otherwise we might have noticed earlier)
> 
>  target/s390x/tcg/mem_helper.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/target/s390x/tcg/mem_helper.c b/target/s390x/tcg/mem_helper.c
> index 9542fad59b..cb82cd1c1d 100644
> --- a/target/s390x/tcg/mem_helper.c
> +++ b/target/s390x/tcg/mem_helper.c
> @@ -51,7 +51,7 @@ static inline bool psw_key_valid(CPUS390XState *env, uint8_t psw_key)
>  
>      if (env->psw.mask & PSW_MASK_PSTATE) {
>          /* PSW key has range 0..15, it is valid if the bit is 1 in the PKM */
> -        return pkm & (0x80 >> psw_key);
> +        return pkm & (0x8000 >> psw_key);
>      }
>      return true;
>  }