arm64: alternative: put secondary CPUs into polling loop during patch

When patching the kernel text with alternatives, we may end up patching
parts of the stop_machine state machine (e.g. atomic_dec_and_test in
ack_state) and consequently corrupt the instruction stream of any
secondary CPUs.

This patch passes the cpu_online_mask to stop_machine, forcing all of
the CPUs into our own callback which can place the secondary cores into
a dumb (but safe!) polling loop whilst the patching is carried out.

Signed-off-by: Will Deacon <will.deacon@arm.com>

1 files changed, 2 insertions, 1 deletions

diff --git a/arch/arm64/include/asm/alternative.h b/arch/arm64/include/asm/alternative.h
index b474e9106bc2..d56ec0715157 100644
--- a/arch/arm64/include/asm/alternative.h
+++ b/arch/arm64/include/asm/alternative.h
@@ -3,6 +3,7 @@
 
 #ifndef __ASSEMBLY__
 
+#include <linux/init.h>
 #include <linux/kconfig.h>
 #include <linux/types.h>
 #include <linux/stddef.h>
@@ -16,7 +17,7 @@ struct alt_instr {
 	u8  alt_len;		/* size of new instruction(s), <= orig_len */
 };
 
-void apply_alternatives_all(void);
+void __init apply_alternatives_all(void);
 void apply_alternatives(void *start, size_t length);
 void free_alternatives_memory(void);