[PATCH] ARM SMP: Add support for startup of secondary processors
Create a temporary page table to startup secondary processors. This
page table must have a 1:1 virtual/physical mapping for the kernel
in addition to the standard mappings to ensure that the secondary
CPU can enable its MMU safely.
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c
index ecc8c33..45ed036 100644
--- a/arch/arm/kernel/smp.c
+++ b/arch/arm/kernel/smp.c
@@ -24,6 +24,9 @@
#include <asm/atomic.h>
#include <asm/cacheflush.h>
#include <asm/cpu.h>
+#include <asm/mmu_context.h>
+#include <asm/pgtable.h>
+#include <asm/pgalloc.h>
#include <asm/processor.h>
#include <asm/tlbflush.h>
#include <asm/ptrace.h>
@@ -37,6 +40,13 @@
cpumask_t cpu_online_map;
/*
+ * as from 2.5, kernels no longer have an init_tasks structure
+ * so we need some other way of telling a new secondary core
+ * where to place its SVC stack
+ */
+struct secondary_data secondary_data;
+
+/*
* structures for inter-processor calls
* - A collection of single bit ipi messages.
*/
@@ -71,6 +81,8 @@
int __init __cpu_up(unsigned int cpu)
{
struct task_struct *idle;
+ pgd_t *pgd;
+ pmd_t *pmd;
int ret;
/*
@@ -84,9 +96,54 @@
}
/*
+ * 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);
+ pmd = pmd_offset(pgd, PHYS_OFFSET);
+ *pmd = __pmd((PHYS_OFFSET & PGDIR_MASK) |
+ PMD_TYPE_SECT | PMD_SECT_AP_WRITE);
+
+ /*
+ * We need to tell the secondary core where to find
+ * its stack and the page tables.
+ */
+ secondary_data.stack = (void *)idle->thread_info + THREAD_SIZE - 8;
+ secondary_data.pgdir = virt_to_phys(pgd);
+ wmb();
+
+ /*
* Now bring the CPU into our world.
*/
ret = boot_secondary(cpu, idle);
+ if (ret == 0) {
+ unsigned long timeout;
+
+ /*
+ * CPU was successfully started, wait for it
+ * to come online or time out.
+ */
+ timeout = jiffies + HZ;
+ while (time_before(jiffies, timeout)) {
+ if (cpu_online(cpu))
+ break;
+
+ udelay(10);
+ barrier();
+ }
+
+ if (!cpu_online(cpu))
+ ret = -EIO;
+ }
+
+ secondary_data.stack = 0;
+ secondary_data.pgdir = 0;
+
+ *pmd_offset(pgd, PHYS_OFFSET) = __pmd(0);
+ pgd_free(pgd);
+
if (ret) {
printk(KERN_CRIT "cpu_up: processor %d failed to boot\n", cpu);
/*
@@ -98,6 +155,56 @@
}
/*
+ * This is the secondary CPU boot entry. We're using this CPUs
+ * idle thread stack, but a set of temporary page tables.
+ */
+asmlinkage void __init secondary_start_kernel(void)
+{
+ struct mm_struct *mm = &init_mm;
+ unsigned int cpu = smp_processor_id();
+
+ printk("CPU%u: Booted secondary processor\n", cpu);
+
+ /*
+ * All kernel threads share the same mm context; grab a
+ * reference and switch to it.
+ */
+ atomic_inc(&mm->mm_users);
+ atomic_inc(&mm->mm_count);
+ current->active_mm = mm;
+ cpu_set(cpu, mm->cpu_vm_mask);
+ cpu_switch_mm(mm->pgd, mm);
+ enter_lazy_tlb(mm, current);
+
+ cpu_init();
+
+ /*
+ * Give the platform a chance to do its own initialisation.
+ */
+ platform_secondary_init(cpu);
+
+ /*
+ * Enable local interrupts.
+ */
+ local_irq_enable();
+ local_fiq_enable();
+
+ calibrate_delay();
+
+ smp_store_cpu_info(cpu);
+
+ /*
+ * OK, now it's safe to let the boot CPU continue
+ */
+ cpu_set(cpu, cpu_online_map);
+
+ /*
+ * OK, it's off to the idle thread for us
+ */
+ cpu_idle();
+}
+
+/*
* Called by both boot and secondaries to move global data into
* per-processor storage.
*/