From: Will Deacon <will.deacon@arm.com>
Date: Tue, 4 Aug 2015 17:52:09 +0000 (+0100)
Subject: arm64: alternatives: ensure secondary CPUs execute ISB after patching
X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=04b8637be92f284409651088f3856f4290a931d8;p=GitHub%2Fexynos8895%2Fandroid_kernel_samsung_universal8895.git

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>
---

diff --git a/arch/arm64/kernel/alternative.c b/arch/arm64/kernel/alternative.c
index fa1d575ab2c2..ab9db0e9818c 100644
--- a/arch/arm64/kernel/alternative.c
+++ b/arch/arm64/kernel/alternative.c
@@ -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);