[PATCH v2 1/2] arm64: add an MTE support check to the top of mte_thread_switch()

[Peter Collingbourne]

This lets us avoid doing unnecessary work on hardware that does
not support MTE, and will allow us to freely use MTE instructions
in the code called by mte_thread_switch().

Signed-off-by: Peter Collingbourne <pcc at google.com>
Link: https://linux-review.googlesource.com/id/I02fd000d1ef2c86c7d2952a7f099b254ec227a5d
---
 arch/arm64/kernel/mte.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/arm64/kernel/mte.c b/arch/arm64/kernel/mte.c
index 9d314a3bad3b..8fc2d90eeb00 100644
--- a/arch/arm64/kernel/mte.c
+++ b/arch/arm64/kernel/mte.c
@@ -199,6 +199,9 @@ void mte_thread_init_user(void)
 
 void mte_thread_switch(struct task_struct *next)
 {
+	if (!system_supports_mte())
+		return;
+
 	mte_update_sctlr_user(next);
 
 	/*
-- 
2.33.0.309.g3052b89438-goog