Commit e16d02ee authored by Heiko Carstens's avatar Heiko Carstens Committed by Vasily Gorbik
Browse files

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: default avatarHeiko Carstens <hca@linux.ibm.com>
Signed-off-by: default avatarVasily Gorbik <gor@linux.ibm.com>
parent fbbd1407

arch/s390/include/asm/text-patching.h

0 → 100644
+16 −0
Original line number Diff line number Diff line 
/* 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 */

arch/s390/kernel/alternative.c

+20 −0
Original line number Diff line number Diff line 
// SPDX-License-Identifier: GPL-2.0

#include <linux/module.h>

#include <linux/cpu.h>

#include <linux/smp.h>

#include <asm/text-patching.h>

#include <asm/alternative.h>

#include <asm/facility.h>

#include <asm/nospec-branch.h>
@@ -110,3 +113,20 @@ void __init apply_alternative_instructions(void) 
{

	apply_alternatives(__alt_instructions, __alt_instructions_end);

}



static void do_sync_core(void *info)

{

	sync_core();

}



void text_poke_sync(void)

{

	on_each_cpu(do_sync_core, NULL, 1);

}



void text_poke_sync_lock(void)

{

	cpus_read_lock();

	text_poke_sync();

	cpus_read_unlock();

}