From 6f20e7f2e930211613a66d0603fa4abaaf3ce662 Mon Sep 17 00:00:00 2001
From: Gavin Shan <gwshan@linux.vnet.ibm.com>
Date: Thu, 8 Jan 2015 16:40:51 +1100
Subject: [PATCH] powerpc/kernel: Avoid memory corruption at early stage

When calling to early_setup(), we pick "boot_paca" up for the master CPU
and initialize that with initialise_paca(). At that point, the SLB
shadow buffer isn't populated yet. Updating the SLB shadow buffer should
corrupt what we had in physical address 0 where the trap instruction is
usually stored.

This hasn't been observed to cause any trouble in practice, but is
obviously fishy.

Fixes: 6f4441ef7009 ("powerpc: Dynamically allocate slb_shadow from memblock")
Signed-off-by: Gavin Shan <gwshan@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
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