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arm64: alternatives: ensure secondary CPUs execute ISB after patching

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In order to guarantee that the patched instruction stream is visible to
a CPU, that CPU must execute an isb instruction after any related cache
maintenance has completed.

The instruction patching routines in kernel/insn.c get this right for
things like jump labels and ftrace, but the alternatives patching omits
it entirely leaving secondary cores in a potential limbo between the old
and the new code.

This patch adds an isb following the secondary polling loop in the
altenatives patching.

Signed-off-by: Will Deacon <will.deacon@arm.com>
This commit is contained in:
Will Deacon 2015-08-04 18:52:09 +01:00
parent 7f08a414f2
commit 04b8637be9
1 changed files with 1 additions and 0 deletions
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arch/arm64/kernel/alternative.c
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@ -132,6 +132,7 @@ static int __apply_alternatives_multi_stop(void *unused)
if (smp_processor_id()) {
while (!READ_ONCE(patched))
cpu_relax();
isb();
} else {
BUG_ON(patched);
__apply_alternatives(&region);