arm64: alternatives: ensure secondary CPUs execute ISB after patching
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>
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@ -132,6 +132,7 @@ static int __apply_alternatives_multi_stop(void *unused)
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if (smp_processor_id()) {
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while (!READ_ONCE(patched))
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cpu_relax();
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isb();
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} else {
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BUG_ON(patched);
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__apply_alternatives(®ion);
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