Re: [PATCH v7 06/27] arm64/sve: Clarify role of the VQ map maintenance functions

Andrew Jones
2019-04-04T21:22:05Z

On Fri, Mar 29, 2019 at 01:00:31PM +0000, Dave Martin wrote:
> The roles of sve_init_vq_map(), sve_update_vq_map() and
> sve_verify_vq_map() are highly non-obvious to anyone who has not dug
> through cpufeatures.c in detail.
>
> Since the way these functions interact with each other is more
> important here than a full understanding of the cpufeatures code, this
> patch adds comments to make the functions' roles clearer.
>
> No functional change.
>
> Signed-off-by: Dave Martin <Dave.Martin@arm.com>
> Reviewed-by: Julien Thierry <julien.thierry@arm.com>
> Reviewed-by: Julien Grall <julien.grall@arm.com>
> Tested-by: zhang.lei <zhang.lei@jp.fujitsu.com>
>
> ---
>
> Changes since v5:
>
> * [Julien Thierry] This patch is useful for explaining the previous
> patch (as per the v5 ordering), and is anyway non-functional.
> Swapped it with the previous patch to provide a more logical reading
> order for the series.
> ---
> arch/arm64/kernel/fpsimd.c | 10 +++++++++-
> 1 file changed, 9 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c
> index 62c37f0..f59ea67 100644
> --- a/arch/arm64/kernel/fpsimd.c
> +++ b/arch/arm64/kernel/fpsimd.c
> @@ -647,6 +647,10 @@ static void sve_probe_vqs(DECLARE_BITMAP(map, SVE_VQ_MAX))
> }
> }
>
> +/*
> + * Initialise the set of known supported VQs for the boot CPU.
> + * This is called during kernel boot, before secondary CPUs are brought up.
> + */
> void __init sve_init_vq_map(void)
> {
> sve_probe_vqs(sve_vq_map);
> @@ -655,6 +659,7 @@ void __init sve_init_vq_map(void)
> /*
> * If we haven't committed to the set of supported VQs yet, filter out
> * those not supported by the current CPU.
> + * This function is called during the bring-up of early secondary CPUs only.
> */
> void sve_update_vq_map(void)
> {
> @@ -662,7 +667,10 @@ void sve_update_vq_map(void)
> bitmap_and(sve_vq_map, sve_vq_map, sve_secondary_vq_map, SVE_VQ_MAX);
> }
>
> -/* Check whether the current CPU supports all VQs in the committed set */
> +/*
> + * Check whether the current CPU supports all VQs in the committed set.
> + * This function is called during the bring-up of late secondary CPUs only.
> + */
> int sve_verify_vq_map(void)
> {
> int ret = 0;
> --
> 2.1.4

Reviewed-by: Andrew Jones <drjones@redhat.com>