[PATCH] x86: fix PDA variables to work during boot

The current PDA code, which went in in post 2.6.19 has a flaw in that it
doesn't correctly cycle the GDT and %GS segment through the boot PDA,
the CPU PDA and finally the per-cpu PDA.

The bug generally doesn't show up if the boot CPU id is zero, but
everything falls apart for a non zero boot CPU id.  The basically kills
voyager which is perfectly capable of doing non zero CPU id boots, so
voyager currently won't boot without this.

The fix is to be careful and actually do the GDT setups correctly.

Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>
Cc: Andi Kleen <ak@suse.de>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/arch/i386/kernel/cpu/common.c b/arch/i386/kernel/cpu/common.c
index 8689d62abd4adc66729c5a58185612ddfd6271d6..8a8bbdaaf38aba279fa3df1672f05a0cdc5253cb 100644 (file)
--- a/arch/i386/kernel/cpu/common.c
+++ b/arch/i386/kernel/cpu/common.c
@@ -710,11 +710,8 @@ __cpuinit int init_gdt(int cpu, struct task_struct *idle)
        return 1;
 }
 
-/* Common CPU init for both boot and secondary CPUs */
-static void __cpuinit _cpu_init(int cpu, struct task_struct *curr)
+void __cpuinit cpu_set_gdt(int cpu)
 {
-       struct tss_struct * t = &per_cpu(init_tss, cpu);
-       struct thread_struct *thread = &curr->thread;
        struct Xgt_desc_struct *cpu_gdt_descr = &per_cpu(cpu_gdt_descr, cpu);
 
        /* Reinit these anyway, even if they've already been done (on
@@ -722,6 +719,13 @@ static void __cpuinit _cpu_init(int cpu, struct task_struct *curr)
           the real ones). */
        load_gdt(cpu_gdt_descr);
        set_kernel_gs();
+}
+
+/* Common CPU init for both boot and secondary CPUs */
+static void __cpuinit _cpu_init(int cpu, struct task_struct *curr)
+{
+       struct tss_struct * t = &per_cpu(init_tss, cpu);
+       struct thread_struct *thread = &curr->thread;
 
        if (cpu_test_and_set(cpu, cpu_initialized)) {
                printk(KERN_WARNING "CPU#%d already initialized!\n", cpu);
@@ -807,6 +811,7 @@ void __cpuinit cpu_init(void)
                        local_irq_enable();
        }
 
+       cpu_set_gdt(cpu);
        _cpu_init(cpu, curr);
 }
 

diff --git a/arch/i386/kernel/smpboot.c b/arch/i386/kernel/smpboot.c
index dea7ef9d3e82804ea6b87089cafd88c435223113..8c6c8c52b95c0b574b837c279f84647d3b4ba867 100644 (file)
--- a/arch/i386/kernel/smpboot.c
+++ b/arch/i386/kernel/smpboot.c
@@ -595,6 +595,12 @@ static void __cpuinit start_secondary(void *unused)
  */
 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.
@@ -972,9 +978,6 @@ static int __cpuinit do_boot_cpu(int apicid, int cpu)
        /* 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;

diff --git a/arch/i386/mach-voyager/voyager_smp.c b/arch/i386/mach-voyager/voyager_smp.c
index 55428e656a3f9a90bddcb50770e92e7434fab16c..74aeedf277f424896c1beaf01580468ecfbe90b5 100644 (file)
--- a/arch/i386/mach-voyager/voyager_smp.c
+++ b/arch/i386/mach-voyager/voyager_smp.c
@@ -772,6 +772,12 @@ initialize_secondary(void)
        set_current(hard_get_current());
 #endif
 
+       /*
+        * 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.

diff --git a/include/asm-i386/processor.h b/include/asm-i386/processor.h
index a52d65440429b99520ff6fa355ccd95d92611619..359f10b54f59ba7c99297dac910b73e4c0406796 100644 (file)
--- a/include/asm-i386/processor.h
+++ b/include/asm-i386/processor.h
@@ -743,6 +743,7 @@ extern void enable_sep_cpu(void);
 extern int sysenter_setup(void);
 
 extern int init_gdt(int cpu, struct task_struct *idle);
+extern void cpu_set_gdt(int);
 extern void secondary_cpu_init(void);
 
 #endif /* __ASM_I386_PROCESSOR_H */