[PATCH] powerpc/book3s64/kuap: SPRN_AMR modification need CSI instructions before and after

[Aneesh Kumar K.V]

As per the ISA, context synchronizing instructions is needed before and after
SPRN_AMR update. Use isync before and the CSI after is implied by the rfid
that we will use to switch to a new context.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar at linux.ibm.com>
---
 arch/powerpc/include/asm/book3s/64/kup-radix.h | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/include/asm/book3s/64/kup-radix.h b/arch/powerpc/include/asm/book3s/64/kup-radix.h
index 3bcef989a35d..224658efe2fd 100644
--- a/arch/powerpc/include/asm/book3s/64/kup-radix.h
+++ b/arch/powerpc/include/asm/book3s/64/kup-radix.h
@@ -16,6 +16,7 @@
 #ifdef CONFIG_PPC_KUAP
 	BEGIN_MMU_FTR_SECTION_NESTED(67)
 	ld	\gpr, STACK_REGS_KUAP(r1)
+	isync
 	mtspr	SPRN_AMR, \gpr
 	END_MMU_FTR_SECTION_NESTED_IFSET(MMU_FTR_RADIX_KUAP, 67)
 #endif
@@ -62,8 +63,14 @@
 
 static inline void kuap_restore_amr(struct pt_regs *regs)
 {
-	if (mmu_has_feature(MMU_FTR_RADIX_KUAP))
+	if (mmu_has_feature(MMU_FTR_RADIX_KUAP)) {
+		isync();
 		mtspr(SPRN_AMR, regs->kuap);
+		/*
+		 * No following isync/CSI required because we will be
+		 * returning to a different context using rfid
+		 */
+	}
 }
 
 static inline void kuap_check_amr(void)
-- 
2.25.2