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>
This commit is contained in:
Heiko Carstens 2021-10-01 12:47:01 +02:00 committed by Vasily Gorbik
parent fbbd140737
commit e16d02ee3f
2 changed files with 36 additions and 0 deletions

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@ -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 */

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@ -1,5 +1,8 @@
// 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();
}