s390/runtime_instrumentation: fix storage key handling

[ Upstream commit 9eaba29c ]

The key member of the runtime instrumentation control block contains
only the access key, not the complete storage key. Therefore the value
must be shifted by four bits.
Note: this is only relevant for debugging purposes in case somebody
compiles a kernel with a default storage access key set to a value not
equal to zero.

Fixes: e4b8b3f3 ("s390: add support for runtime instrumentation")
Reported-by: NClaudio Imbrenda <imbrenda@linux.ibm.com>
Signed-off-by: NHeiko Carstens <hca@linux.ibm.com>
Signed-off-by: NSasha Levin <sashal@kernel.org>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

arch/s390/kernel/runtime_instr.c

@@ -57,7 +57,7 @@ static void init_runtime_instr_cb(struct runtime_instr_cb *cb)
 	cb->k = 1;
 	cb->ps = 1;
 	cb->pc = 1;
-	cb->key = PAGE_DEFAULT_KEY;
+	cb->key = PAGE_DEFAULT_KEY >> 4;
 	cb->v = 1;
 }