Commit 4e8ee7de authored by Will Deacon's avatar Will Deacon
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ARM: SMP: use idmap_pgd for mapping MMU enable during secondary booting 



The ARM SMP booting code allocates a temporary set of page tables
containing an identity mapping of the kernel image and provides this
to secondary CPUs for initial booting.

In reality, we only need to include the __turn_mmu_on function in the
identity mapping since the rest of the kernel is executing from virtual
addresses after this point.

This patch adds __turn_mmu_on to the .idmap.text section, allowing the
SMP booting code to use the idmap_pgd directly and not have to populate
its own set of page table.

As a result of this patch, we can make the identity_mapping_add function
static (since it is only used within mm/idmap.c) and also remove the
identity_mapping_del function. The identity map population is moved to
an early initcall so that it is setup in time for secondary CPU bringup.

Reviewed-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
Signed-off-by: default avatarWill Deacon <will.deacon@arm.com>
parent 72662e01

arch/arm/include/asm/idmap.h

+0 −3
Original line number Diff line number Diff line
@@ -9,9 +9,6 @@ 


extern pgd_t *idmap_pgd;



void identity_mapping_add(pgd_t *, unsigned long, unsigned long);

void identity_mapping_del(pgd_t *, unsigned long, unsigned long);



void setup_mm_for_reboot(void);



#endif	/* __ASM_IDMAP_H */

arch/arm/kernel/head.S

+3 −1
Original line number Diff line number Diff line
@@ -398,7 +398,8 @@ ENDPROC(__enable_mmu) 
 * other registers depend on the function called upon completion

 */

	.align	5

__turn_mmu_on:

	.pushsection	.idmap.text, "ax"

ENTRY(__turn_mmu_on)

	mov	r0, r0

	mcr	p15, 0, r0, c1, c0, 0		@ write control reg

	mrc	p15, 0, r3, c0, c0, 0		@ read id reg
@@ -407,6 +408,7 @@ __turn_mmu_on: 
	mov	pc, r3

__turn_mmu_on_end:

ENDPROC(__turn_mmu_on)

	.popsection





#ifdef CONFIG_SMP_ON_UP

arch/arm/kernel/smp.c

+1 −30
Original line number Diff line number Diff line
@@ -62,7 +62,6 @@ int __cpuinit __cpu_up(unsigned int cpu) 
{

	struct cpuinfo_arm *ci = &per_cpu(cpu_data, cpu);

	struct task_struct *idle = ci->idle;

	pgd_t *pgd;

	int ret;



	/*
@@ -84,30 +83,12 @@ int __cpuinit __cpu_up(unsigned int cpu) 
		init_idle(idle, cpu);

	}



	/*

	 * Allocate initial page tables to allow the new CPU to

	 * enable the MMU safely.  This essentially means a set

	 * of our "standard" page tables, with the addition of

	 * a 1:1 mapping for the physical address of the kernel.

	 */

	pgd = pgd_alloc(&init_mm);

	if (!pgd)

		return -ENOMEM;



	if (PHYS_OFFSET != PAGE_OFFSET) {

#ifndef CONFIG_HOTPLUG_CPU

		identity_mapping_add(pgd, __pa(__init_begin), __pa(__init_end));

#endif

		identity_mapping_add(pgd, __pa(_stext), __pa(_etext));

		identity_mapping_add(pgd, __pa(_sdata), __pa(_edata));

	}



	/*

	 * We need to tell the secondary core where to find

	 * its stack and the page tables.

	 */

	secondary_data.stack = task_stack_page(idle) + THREAD_START_SP;

	secondary_data.pgdir = virt_to_phys(pgd);

	secondary_data.pgdir = virt_to_phys(idmap_pgd);

	secondary_data.swapper_pg_dir = virt_to_phys(swapper_pg_dir);

	__cpuc_flush_dcache_area(&secondary_data, sizeof(secondary_data));

	outer_clean_range(__pa(&secondary_data), __pa(&secondary_data + 1));
@@ -143,16 +124,6 @@ int __cpuinit __cpu_up(unsigned int cpu) 
	secondary_data.stack = NULL;

	secondary_data.pgdir = 0;



	if (PHYS_OFFSET != PAGE_OFFSET) {

#ifndef CONFIG_HOTPLUG_CPU

		identity_mapping_del(pgd, __pa(__init_begin), __pa(__init_end));

#endif

		identity_mapping_del(pgd, __pa(_stext), __pa(_etext));

		identity_mapping_del(pgd, __pa(_sdata), __pa(_edata));

	}



	pgd_free(&init_mm, pgd);



	return ret;

}

arch/arm/mm/idmap.c

+2 −32
Original line number Diff line number Diff line
@@ -32,7 +32,7 @@ static void idmap_add_pud(pgd_t *pgd, unsigned long addr, unsigned long end, 
	} while (pud++, addr = next, addr != end);

}



void identity_mapping_add(pgd_t *pgd, unsigned long addr, unsigned long end)

static void identity_mapping_add(pgd_t *pgd, unsigned long addr, unsigned long end)

{

	unsigned long prot, next;
@@ -47,36 +47,6 @@ void identity_mapping_add(pgd_t *pgd, unsigned long addr, unsigned long end) 
	} while (pgd++, addr = next, addr != end);

}



#ifdef CONFIG_SMP

static void idmap_del_pmd(pud_t *pud, unsigned long addr, unsigned long end)

{

	pmd_t *pmd = pmd_offset(pud, addr);

	pmd_clear(pmd);

}



static void idmap_del_pud(pgd_t *pgd, unsigned long addr, unsigned long end)

{

	pud_t *pud = pud_offset(pgd, addr);

	unsigned long next;



	do {

		next = pud_addr_end(addr, end);

		idmap_del_pmd(pud, addr, next);

	} while (pud++, addr = next, addr != end);

}



void identity_mapping_del(pgd_t *pgd, unsigned long addr, unsigned long end)

{

	unsigned long next;



	pgd += pgd_index(addr);

	do {

		next = pgd_addr_end(addr, end);

		idmap_del_pud(pgd, addr, next);

	} while (pgd++, addr = next, addr != end);

}

#endif



extern char  __idmap_text_start[], __idmap_text_end[];



static int __init init_static_idmap(void)
@@ -97,7 +67,7 @@ static int __init init_static_idmap(void) 


	return 0;

}

arch_initcall(init_static_idmap);

early_initcall(init_static_idmap);



/*

 * In order to soft-boot, we need to switch to a 1:1 mapping for the

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