[kvm-unit-tests PATCH 1/6] arm64: Remove unnecessary ISB when writing to SPSel

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Software can use the SPSel operand to write directly to PSTATE.SP.
According to ARM DDI 0487F.b, page D1-2332, writes to PSTATE are
self-synchronizing and no ISB is needed:

"Writes to the PSTATE fields have side-effects on various aspects of the PE
operation. All of these side-effects are guaranteed:
- Not to be visible to earlier instructions in the execution stream.
- To be visible to later instructions in the execution stream."

Signed-off-by: Alexandru Elisei <alexandru.elisei@xxxxxxx>
---
 arm/cstart64.S | 1 -
 1 file changed, 1 deletion(-)

diff --git a/arm/cstart64.S b/arm/cstart64.S
index 0428014aa58a..fc1930bcdb53 100644
--- a/arm/cstart64.S
+++ b/arm/cstart64.S
@@ -54,7 +54,6 @@ start:
 	/* set up stack */
 	mov	x4, #1
 	msr	spsel, x4
-	isb
 	adrp    x4, stackptr
 	add     sp, x4, :lo12:stackptr
 
-- 
2.30.1




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