Re: [PATCH v3 11/20] target/arm: default SVE length to 64 bytes for linux-user

[Richard Henderson]

On 12/11/19 9:05 AM, Alex Bennée wrote:
> The Linux kernel chooses the default of 64 bytes for SVE registers on
> the basis that it is the largest size on known hardware that won't
> grow the signal frame. We still honour the sve-max-vq property and
> userspace can expand the number of lanes by calling PR_SVE_SET_VL.
> 
> This should not make any difference to SVE enabled software as the SVE
> is of course vector length agnostic.
> 
> Signed-off-by: Alex Bennée <address@hidden>
> 
> ---
> v2
>   - tweak zcr_el[1] instead
> ---
>  target/arm/cpu.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/target/arm/cpu.c b/target/arm/cpu.c
> index 7a4ac9339bf..d42b88c9b73 100644
> --- a/target/arm/cpu.c
> +++ b/target/arm/cpu.c
> @@ -199,9 +199,9 @@ static void arm_cpu_reset(CPUState *s)
>          /* and to the SVE instructions */
>          env->cp15.cpacr_el1 = deposit64(env->cp15.cpacr_el1, 16, 2, 3);
>          env->cp15.cptr_el[3] |= CPTR_EZ;
> -        /* with maximum vector length */
> +        /* with reasonable vector length */

I think this comment should mention the kernel as well.  Otherwise,

Reviewed-by: Richard Henderson <address@hidden>


r~