linux-kernel - [PATCH v4 14/19] ARM: LPAE: Add SMP support for the 3-level page table format

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Date:	Mon, 24 Jan 2011 17:55:56 +0000
From:	Catalin Marinas <catalin.marinas@....com>
To:	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [PATCH v4 14/19] ARM: LPAE: Add SMP support for the 3-level page table format

With 3-level page tables, starting secondary CPUs required allocating
the pgd as well. Since LPAE Linux uses TTBR1 for the kernel page tables,
this patch reorders the CPU setup call in the head.S file so that the
swapper_pg_dir is used. TTBR0 is set to the value generated by the
primary CPU.

Signed-off-by: Catalin Marinas <catalin.marinas@....com>
---

There was a comment that secondary_startup hunk below should not reorder
the code but pass two registers for TTBR0 and TTBR1. I still find this
approach simpler __v7_setup never programs TTBR0 so it would ignore one
of the registers.

 arch/arm/kernel/head.S |   10 +++++-----
 1 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/arch/arm/kernel/head.S b/arch/arm/kernel/head.S
index d96986c..bade113 100644
--- a/arch/arm/kernel/head.S
+++ b/arch/arm/kernel/head.S
@@ -331,6 +331,10 @@ ENTRY(secondary_startup)
  THUMB( it	eq )		@ force fixup-able long branch encoding
 	beq	__error_p
 
+	pgtbl	r4
+	add	r12, r10, #BSYM(PROCINFO_INITFUNC)
+	blx	r12				@ initialise processor
+						@ (return control reg)
 	/*
 	 * Use the page tables supplied from  __cpu_up.
 	 */
@@ -338,12 +342,8 @@ ENTRY(secondary_startup)
 	ldmia	r4, {r5, r7, r12}		@ address to jump to after
 	sub	r4, r4, r5			@ mmu has been enabled
 	ldr	r4, [r7, r4]			@ get secondary_data.pgdir
-	adr	lr, BSYM(__enable_mmu)		@ return address
 	mov	r13, r12			@ __secondary_switched address
- ARM(	add	pc, r10, #PROCINFO_INITFUNC	) @ initialise processor
-						  @ (return control reg)
- THUMB(	add	r12, r10, #PROCINFO_INITFUNC	)
- THUMB(	mov	pc, r12				)
+	b	__enable_mmu
 ENDPROC(secondary_startup)
 
 	/*

--
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