[PATCH] i386: Use per-cpu GDT immediately upon boot
Now we are no longer dynamically allocating the GDT, we don't need the
"cpu_gdt_table" at all: we can switch straight from "boot_gdt_table" to the
per-cpu GDT. This means initializing the cpu_gdt array in C.
The boot CPU uses the per-cpu var directly, then in smp_prepare_cpus() it
switches to the per-cpu copy just allocated. For secondary CPUs, the
early_gdt_descr is set to point directly to their per-cpu copy.
For UP the code is very simple: it keeps using the "per-cpu" GDT as per SMP,
but we never have to move.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Andi Kleen <ak@suse.de>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
diff --git a/arch/i386/kernel/smpboot.c b/arch/i386/kernel/smpboot.c
index b36a5f1..a9447c3 100644
--- a/arch/i386/kernel/smpboot.c
+++ b/arch/i386/kernel/smpboot.c
@@ -440,12 +440,6 @@
void __devinit initialize_secondary(void)
{
/*
- * switch to the per CPU GDT we already set up
- * in do_boot_cpu()
- */
- cpu_set_gdt(current_thread_info()->cpu);
-
- /*
* We don't actually need to load the full TSS,
* basically just the stack pointer and the eip.
*/
@@ -787,6 +781,32 @@
#define alloc_idle_task(cpu) fork_idle(cpu)
#endif
+/* Initialize the CPU's GDT. This is either the boot CPU doing itself
+ (still using the master per-cpu area), or a CPU doing it for a
+ secondary which will soon come up. */
+static __cpuinit void init_gdt(int cpu, struct task_struct *idle)
+{
+ struct Xgt_desc_struct *cpu_gdt_descr = &per_cpu(cpu_gdt_descr, cpu);
+ struct desc_struct *gdt = per_cpu(cpu_gdt, cpu);
+ struct i386_pda *pda = &per_cpu(_cpu_pda, cpu);
+
+ cpu_gdt_descr->address = (unsigned long)gdt;
+ cpu_gdt_descr->size = GDT_SIZE - 1;
+
+ pack_descriptor((u32 *)&gdt[GDT_ENTRY_PDA].a,
+ (u32 *)&gdt[GDT_ENTRY_PDA].b,
+ (unsigned long)pda, sizeof(*pda) - 1,
+ 0x80 | DESCTYPE_S | 0x2, 0); /* present read-write data segment */
+
+ memset(pda, 0, sizeof(*pda));
+ pda->_pda = pda;
+ pda->cpu_number = cpu;
+ pda->pcurrent = idle;
+}
+
+/* Defined in head.S */
+extern struct Xgt_desc_struct early_gdt_descr;
+
static int __cpuinit do_boot_cpu(int apicid, int cpu)
/*
* NOTE - on most systems this is a PHYSICAL apic ID, but on multiquad
@@ -809,6 +829,8 @@
panic("failed fork for CPU %d", cpu);
init_gdt(cpu, idle);
+ early_gdt_descr.address = (unsigned long)get_cpu_gdt_table(cpu);
+ start_pda = cpu_pda(cpu);
idle->thread.eip = (unsigned long) start_secondary;
/* start_eip had better be page-aligned! */
@@ -1161,13 +1183,26 @@
smp_boot_cpus(max_cpus);
}
-void __devinit smp_prepare_boot_cpu(void)
+/* Current gdt points %fs at the "master" per-cpu area: after this,
+ * it's on the real one. */
+static inline void switch_to_new_gdt(void)
{
- cpu_set(smp_processor_id(), cpu_online_map);
- cpu_set(smp_processor_id(), cpu_callout_map);
- cpu_set(smp_processor_id(), cpu_present_map);
- cpu_set(smp_processor_id(), cpu_possible_map);
- per_cpu(cpu_state, smp_processor_id()) = CPU_ONLINE;
+ load_gdt(&per_cpu(cpu_gdt_descr, smp_processor_id()));
+ asm volatile ("mov %0, %%fs" : : "r" (__KERNEL_PDA) : "memory");
+}
+
+void __init smp_prepare_boot_cpu(void)
+{
+ unsigned int cpu = smp_processor_id();
+
+ init_gdt(cpu, current);
+ switch_to_new_gdt();
+
+ cpu_set(cpu, cpu_online_map);
+ cpu_set(cpu, cpu_callout_map);
+ cpu_set(cpu, cpu_present_map);
+ cpu_set(cpu, cpu_possible_map);
+ __get_cpu_var(cpu_state) = CPU_ONLINE;
}
#ifdef CONFIG_HOTPLUG_CPU