This is a note to let you know that I've just added the patch titled
powerpc: Add isync to copy_and_flush
to the 3.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
powerpc-add-isync-to-copy_and_flush.patch
and it can be found in the queue-3.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 29ce3c5073057991217916abc25628e906911757 Mon Sep 17 00:00:00 2001
From: Michael Neuling <michael.neuling@xxxxxxxxxxx>
Date: Wed, 24 Apr 2013 00:30:09 +0000
Subject: powerpc: Add isync to copy_and_flush
From: Michael Neuling <michael.neuling@xxxxxxxxxxx>
commit 29ce3c5073057991217916abc25628e906911757 upstream.
In __after_prom_start we copy the kernel down to zero in two calls to
copy_and_flush. After the first call (copy from 0 to copy_to_here:)
we jump to the newly copied code soon after.
Unfortunately there's no isync between the copy of this code and the
jump to it. Hence it's possible that stale instructions could still be
in the icache or pipeline before we branch to it.
We've seen this on real machines and it's results in no console output
after:
calling quiesce...
returning from prom_init
The below adds an isync to ensure that the copy and flushing has
completed before any branching to the new instructions occurs.
Signed-off-by: Michael Neuling <mikey@xxxxxxxxxxx>
Signed-off-by: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/powerpc/kernel/head_64.S | 1 +
1 file changed, 1 insertion(+)
--- a/arch/powerpc/kernel/head_64.S
+++ b/arch/powerpc/kernel/head_64.S
@@ -489,6 +489,7 @@ _GLOBAL(copy_and_flush)
sync
addi r5,r5,8
addi r6,r6,8
+ isync
blr
.align 8
Patches currently in stable-queue which might be from michael.neuling@xxxxxxxxxxx are
queue-3.4/powerpc-add-isync-to-copy_and_flush.patch
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