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

Dave Martin
2019-03-29T13:02:51Z

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