s390: introduce text_poke_sync()

Introduce a text_poke_sync() similar to what x86 has. This can be
used to execute a serializing instruction on all CPUs (including
the current one).

Note: according to the Principles of Operation an IPI (= interrupt)
will already serialize a CPU, however it is better to be explicit. In
addition on_each_cpu() makes sure that also the current CPU get
serialized - just to make sure that possible preemption can prevent
some theoretical case where a CPU will not be serialized.

Therefore text_poke_sync() has to be used whenever code got modified,
just to avoid to rely on implicit serialization.

Also introduce text_poke_sync_lock() which will also disable CPU
hotplug, to prevent that any CPU is just going online with a
prefetched old version of a modified instruction.

Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

1 files changed, 16 insertions, 0 deletions

diff --git a/arch/s390/include/asm/text-patching.h b/arch/s390/include/asm/text-patching.h
new file mode 100644
index 000000000000..b219056a8817
--- /dev/null
+++ b/arch/s390/include/asm/text-patching.h
@@ -0,0 +1,16 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#ifndef _ASM_S390_TEXT_PATCHING_H
+#define _ASM_S390_TEXT_PATCHING_H
+
+#include <asm/barrier.h>
+
+static __always_inline void sync_core(void)
+{
+	bcr_serialize();
+}
+
+void text_poke_sync(void);
+void text_poke_sync_lock(void);
+
+#endif /* _ASM_S390_TEXT_PATCHING_H */