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powerpc: Add isync to copy_and_flush

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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@neuling.org>
CC: <stable@vger.kernel.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
This commit is contained in:
Michael Neuling 2013-04-24 00:30:09 +00:00 committed by Benjamin Herrenschmidt
parent 2171364d1a
commit 29ce3c5073
1 changed files with 1 additions and 0 deletions
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arch/powerpc/kernel/head_64.S
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@ -509,6 +509,7 @@ _GLOBAL(copy_and_flush)
sync sync
addi r5,r5,8 addi r5,r5,8
addi r6,r6,8 addi r6,r6,8
isync
blr blr
.align 8 .align 8