[PATCH 2/2] selftests: vm: pkeys: Fix powerpc access right updates

[Sandipan Das <sandipan@linux.ibm.com>]

The Power ISA mandates that all writes to the Authority
Mask Register (AMR) must always be preceded as well as
succeeded by a context-synchronizing instruction. This
applies to both the privileged and unprivileged variants
of the Move To AMR instruction.

Fixes: 130f573c2a79 ("selftests/vm/pkeys: introduce powerpc support")
Reported-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Suggested-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Signed-off-by: Sandipan Das <sandipan@linux.ibm.com>
---
 tools/testing/selftests/vm/pkey-powerpc.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/vm/pkey-powerpc.h b/tools/testing/selftests/vm/pkey-powerpc.h
index eb5077de8f1e..1ebb586b2fbc 100644
--- a/tools/testing/selftests/vm/pkey-powerpc.h
+++ b/tools/testing/selftests/vm/pkey-powerpc.h
@@ -55,7 +55,8 @@ static inline void __write_pkey_reg(u64 pkey_reg)
 	dprintf4("%s() changing %016llx to %016llx\n",
 			 __func__, __read_pkey_reg(), pkey_reg);
 
-	asm volatile("mtspr 0xd, %0" : : "r" ((unsigned long)(amr)) : "memory");
+	asm volatile("isync; mtspr 0xd, %0; isync"
+		     : : "r" ((unsigned long)(amr)) : "memory");
 
 	dprintf4("%s() pkey register after changing %016llx to %016llx\n",
 			__func__, __read_pkey_reg(), pkey_reg);
-- 
2.17.1