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: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c
index 8afadda..76ff28d 100644
--- a/arch/arm/kernel/smp.c
+++ b/arch/arm/kernel/smp.c
@@ -62,7 +62,6 @@
{
struct cpuinfo_arm *ci = &per_cpu(cpu_data, cpu);
struct task_struct *idle = ci->idle;
- pgd_t *pgd;
int ret;
/*
@@ -85,29 +84,11 @@
}
/*
- * 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 @@
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;
}