[PATCH] i386: Initialize the per-CPU data area

When a CPU is brought up, a PDA and GDT are allocated for it.  The GDT's
__KERNEL_PDA entry is pointed to the allocated PDA memory, so that all
references using this segment descriptor will refer to the PDA.

This patch rearranges CPU initialization a bit, so that the GDT/PDA are set up
as early as possible in cpu_init().  Also for secondary CPUs, GDT+PDA are
preallocated and initialized so all the secondary CPU needs to do is set up
the ldt and load %gs.  This will be important once smp_processor_id() and
current use the PDA.

In all cases, the PDA is set up in head.S, before a CPU starts running C code,
so the PDA is always available.

Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Cc: Chuck Ebbert <76306.1226@compuserve.com>
Cc: Zachary Amsden <zach@vmware.com>
Cc: Jan Beulich <jbeulich@novell.com>
Cc: Andi Kleen <ak@suse.de>
Cc: James Bottomley <James.Bottomley@SteelEye.com>
Cc: Matt Tolentino <matthew.e.tolentino@intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>

1 files changed, 22 insertions, 6 deletions

diff --git a/arch/i386/kernel/smpboot.c b/arch/i386/kernel/smpboot.c
index 4bb8b77cd65b..095636620fa2 100644
--- a/arch/i386/kernel/smpboot.c
+++ b/arch/i386/kernel/smpboot.c
@@ -52,6 +52,7 @@
 #include <asm/desc.h>
 #include <asm/arch_hooks.h>
 #include <asm/nmi.h>
+#include <asm/pda.h>
 
 #include <mach_apic.h>
 #include <mach_wakecpu.h>
@@ -536,11 +537,11 @@ set_cpu_sibling_map(int cpu)
 static void __devinit start_secondary(void *unused)
 {
         /*
-         * Dont put anything before smp_callin(), SMP
+         * Don't put *anything* before secondary_cpu_init(), SMP
          * booting is too fragile that we want to limit the
          * things done here to the most necessary things.
          */
-        cpu_init();
+        secondary_cpu_init();
         preempt_disable();
         smp_callin();
         while (!cpu_isset(smp_processor_id(), smp_commenced_mask))
@@ -599,13 +600,16 @@ void __devinit initialize_secondary(void)
                 "movl %0,%%esp\n\t"
                 "jmp *%1"
                 :
-                :"r" (current->thread.esp),"r" (current->thread.eip));
+                :"m" (current->thread.esp),"m" (current->thread.eip));
 }
 
+/* Static state in head.S used to set up a CPU */
 extern struct {
         void * esp;
         unsigned short ss;
 } stack_start;
+extern struct i386_pda *start_pda;
+extern struct Xgt_desc_struct cpu_gdt_descr;
 
 #ifdef CONFIG_NUMA
 
@@ -936,9 +940,6 @@ static int __devinit do_boot_cpu(int apicid, int cpu)
         unsigned long start_eip;
         unsigned short nmi_high = 0, nmi_low = 0;
 
-        ++cpucount;
-        alternatives_smp_switch(1);
-
         /*
          * We can't use kernel_thread since we must avoid to
          * reschedule the child.
@@ -946,15 +947,30 @@ static int __devinit do_boot_cpu(int apicid, int cpu)
         idle = alloc_idle_task(cpu);
         if (IS_ERR(idle))
                 panic("failed fork for CPU %d", cpu);
+
+        /* Pre-allocate and initialize the CPU's GDT and PDA so it
+           doesn't have to do any memory allocation during the
+           delicate CPU-bringup phase. */
+        if (!init_gdt(cpu, idle)) {
+                printk(KERN_INFO "Couldn't allocate GDT/PDA for CPU %d\n", cpu);
+                return -1;      /* ? */
+        }
+
         idle->thread.eip = (unsigned long) start_secondary;
         /* start_eip had better be page-aligned! */
         start_eip = setup_trampoline();
 
+        ++cpucount;
+        alternatives_smp_switch(1);
+
         /* So we see what's up   */
         printk("Booting processor %d/%d eip %lx\n", cpu, apicid, start_eip);
         /* Stack for startup_32 can be just as for start_secondary onwards */
         stack_start.esp = (void *) idle->thread.esp;
 
+        start_pda = cpu_pda(cpu);
+        cpu_gdt_descr = per_cpu(cpu_gdt_descr, cpu);
+
         irq_ctx_init(cpu);
 
         x86_cpu_to_apicid[cpu] = apicid;