[PATCH] arm64/fp: Add comments documenting the usage of state restore functions

* [PATCH] arm64/fp: Add comments documenting the usage of state restore functions
@ 2021-12-07 16:32 Mark Brown
  2021-12-14 19:17 ` Catalin Marinas
  0 siblings, 1 reply; 2+ messages in thread
From: Mark Brown @ 2021-12-07 16:32 UTC (permalink / raw)
  To: Catalin Marinas, Will Deacon; +Cc: linux-arm-kernel, Mark Brown

Add comments to help people figure out when fpsimd_bind_state_to_cpu() and
fpsimd_update_current_state() are used.

Signed-off-by: Mark Brown <broonie@kernel.org>
---
 arch/arm64/kernel/fpsimd.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c
index 6fb361e8bed8..d3573f19e831 100644
--- a/arch/arm64/kernel/fpsimd.c
+++ b/arch/arm64/kernel/fpsimd.c
@@ -1217,7 +1217,8 @@ void fpsimd_bind_state_to_cpu(struct user_fpsimd_state *st, void *sve_state,
 /*
  * Load the userland FPSIMD state of 'current' from memory, but only if the
  * FPSIMD state already held in the registers is /not/ the most recent FPSIMD
- * state of 'current'
+ * state of 'current'.  This is called when we are preparing to return to
+ * userspace to ensure that userspace sees a good register state.
  */
 void fpsimd_restore_current_state(void)
 {
@@ -1248,7 +1249,9 @@ void fpsimd_restore_current_state(void)
 /*
  * Load an updated userland FPSIMD state for 'current' from memory and set the
  * flag that indicates that the FPSIMD register contents are the most recent
- * FPSIMD state of 'current'
+ * FPSIMD state of 'current'. This is used by the signal code to restore the
+ * register state when returning from a signal handler in FPSIMD only cases,
+ * any SVE context will be discarded.
  */
 void fpsimd_update_current_state(struct user_fpsimd_state const *state)
 {
-- 
2.30.2


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