linux-kernel - [012/139] sh: Enable the mmu in start

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Date:	Thu, 22 Apr 2010 12:53:09 -0700
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...nel.org
Cc:	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Matt Fleming <matt@...sole-pimps.org>,
	Paul Mundt <lethal@...ux-sh.org>
Subject: [012/139] sh: Enable the mmu in start_secondary()

2.6.33-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Matt Fleming <matt@...sole-pimps.org>

commit 4bea3418c737891894b9d3d3e9f8bbd67d66fa38 upstream.

For the boot, enable_mmu() is called from setup_arch() but we don't call
setup_arch() for any of the other cpus. So turn on the non-boot cpu's
mmu inside of start_secondary().

I noticed this bug on an SMP board when trying to map I/O memory
(smsc911x registers) into the kernel address space. Since the Address
Translation bit in MMUCR wasn't set, accessing the virtual address where
the smsc911x registers were supposedly mapped actually performed a
physical address access.

Signed-off-by: Matt Fleming <matt@...sole-pimps.org>
Signed-off-by: Paul Mundt <lethal@...ux-sh.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

---
 arch/sh/kernel/smp.c |    1 +
 1 file changed, 1 insertion(+)

--- a/arch/sh/kernel/smp.c
+++ b/arch/sh/kernel/smp.c
@@ -69,6 +69,7 @@ asmlinkage void __cpuinit start_secondar
 	unsigned int cpu;
 	struct mm_struct *mm = &init_mm;

+	enable_mmu();
 	atomic_inc(&mm->mm_count);
 	atomic_inc(&mm->mm_users);
 	current->active_mm = mm;

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