[PATCH] x86: fix broken SMP boot sequence

Recent GDT changes broke the SMP boot sequence if the booting CPU is
numbered anything other than zero.  There's also a subtle source of error
in that the boot time CPU now uses cpu_gdt_table (which is actually the GDT
for booting CPUs in head.S).  This patch fixes both problems by making GDT
descriptors themselves allocated from a per_cpu area and switching to them
in cpu_init(), which now means that cpu_gdt_table is exclusively used for
booting CPUs again.

Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>
Cc: Zachary Amsden <zach@vmware.com>
Cc: Matt Tolentino <metolent@snoqualmie.dp.intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/arch/i386/kernel/cpu/common.c b/arch/i386/kernel/cpu/common.c
index 7eb9213734a321614ea6da6837ccd1bbbdf1dd85..4ecd4b326ded5400a5e3641560c59c5e8621b6cd 100644 (file)
--- a/arch/i386/kernel/cpu/common.c
+++ b/arch/i386/kernel/cpu/common.c
@@ -4,6 +4,7 @@
 #include <linux/smp.h>
 #include <linux/module.h>
 #include <linux/percpu.h>
+#include <linux/bootmem.h>
 #include <asm/semaphore.h>
 #include <asm/processor.h>
 #include <asm/i387.h>
@@ -18,6 +19,9 @@
 
 #include "cpu.h"
 
+DEFINE_PER_CPU(struct Xgt_desc_struct, cpu_gdt_descr);
+EXPORT_PER_CPU_SYMBOL(cpu_gdt_descr);
+
 DEFINE_PER_CPU(unsigned char, cpu_16bit_stack[CPU_16BIT_STACK_SIZE]);
 EXPORT_PER_CPU_SYMBOL(cpu_16bit_stack);
 
@@ -571,8 +575,9 @@ void __devinit cpu_init(void)
        int cpu = smp_processor_id();
        struct tss_struct * t = &per_cpu(init_tss, cpu);
        struct thread_struct *thread = &current->thread;
-       struct desc_struct *gdt = get_cpu_gdt_table(cpu);
+       struct desc_struct *gdt;
        __u32 stk16_off = (__u32)&per_cpu(cpu_16bit_stack, cpu);
+       struct Xgt_desc_struct *cpu_gdt_descr = &per_cpu(cpu_gdt_descr, cpu);
 
        if (cpu_test_and_set(cpu, cpu_initialized)) {
                printk(KERN_WARNING "CPU#%d already initialized!\n", cpu);
@@ -589,6 +594,25 @@ void __devinit cpu_init(void)
                set_in_cr4(X86_CR4_TSD);
        }
 
+       /*
+        * This is a horrible hack to allocate the GDT.  The problem
+        * is that cpu_init() is called really early for the boot CPU
+        * (and hence needs bootmem) but much later for the secondary
+        * CPUs, when bootmem will have gone away
+        */
+       if (NODE_DATA(0)->bdata->node_bootmem_map) {
+               gdt = (struct desc_struct *)alloc_bootmem_pages(PAGE_SIZE);
+               /* alloc_bootmem_pages panics on failure, so no check */
+               memset(gdt, 0, PAGE_SIZE);
+       } else {
+               gdt = (struct desc_struct *)get_zeroed_page(GFP_KERNEL);
+               if (unlikely(!gdt)) {
+                       printk(KERN_CRIT "CPU%d failed to allocate GDT\n", cpu);
+                       for (;;)
+                               local_irq_enable();
+               }
+       }
+
        /*
         * Initialize the per-CPU GDT with the boot GDT,
         * and set up the GDT descriptor:
@@ -601,10 +625,10 @@ void __devinit cpu_init(void)
                ((((__u64)stk16_off) << 32) & 0xff00000000000000ULL) |
                (CPU_16BIT_STACK_SIZE - 1);
 
-       cpu_gdt_descr[cpu].size = GDT_SIZE - 1;
-       cpu_gdt_descr[cpu].address = (unsigned long)gdt;
+       cpu_gdt_descr->size = GDT_SIZE - 1;
+       cpu_gdt_descr->address = (unsigned long)gdt;
 
-       load_gdt(&cpu_gdt_descr[cpu]);
+       load_gdt(cpu_gdt_descr);
        load_idt(&idt_descr);
 
        /*

diff --git a/arch/i386/kernel/efi.c b/arch/i386/kernel/efi.c
index ecad519fd395f6a17607c65737713f5aca26c3d3..e3e42fd6240115f97904eefde20d8828b4bb9f4f 100644 (file)
--- a/arch/i386/kernel/efi.c
+++ b/arch/i386/kernel/efi.c
@@ -103,17 +103,19 @@ static void efi_call_phys_prelog(void)
         */
        local_flush_tlb();
 
-       cpu_gdt_descr[0].address = __pa(cpu_gdt_descr[0].address);
-       load_gdt((struct Xgt_desc_struct *) __pa(&cpu_gdt_descr[0]));
+       per_cpu(cpu_gdt_descr, 0).address =
+                                __pa(per_cpu(cpu_gdt_descr, 0).address);
+       load_gdt((struct Xgt_desc_struct *)__pa(&per_cpu(cpu_gdt_descr, 0)));
 }
 
 static void efi_call_phys_epilog(void)
 {
        unsigned long cr4;
 
-       cpu_gdt_descr[0].address =
-               (unsigned long) __va(cpu_gdt_descr[0].address);
-       load_gdt(&cpu_gdt_descr[0]);
+       per_cpu(cpu_gdt_descr, 0).address =
+                       (unsigned long)__va(per_cpu(cpu_gdt_descr, 0).address);
+       load_gdt((struct Xgt_desc_struct *)__va(&per_cpu(cpu_gdt_descr, 0)));
+
        cr4 = read_cr4();
 
        if (cr4 & X86_CR4_PSE) {

diff --git a/arch/i386/kernel/head.S b/arch/i386/kernel/head.S
index 2bee6499edd98a9b658aaed95787fbd05cb690ac..e0b7c632efbcb63fa6704baae50b300422da624e 100644 (file)
--- a/arch/i386/kernel/head.S
+++ b/arch/i386/kernel/head.S
@@ -534,5 +534,3 @@ ENTRY(cpu_gdt_table)
        .quad 0x0000000000000000        /* 0xf0 - unused */
        .quad 0x0000000000000000        /* 0xf8 - GDT entry 31: double-fault TSS */
 
-       /* Be sure this is zeroed to avoid false validations in Xen */
-       .fill PAGE_SIZE_asm / 8 - GDT_ENTRIES,8,0

diff --git a/arch/i386/kernel/i386_ksyms.c b/arch/i386/kernel/i386_ksyms.c
index 3999bec50c33d4aceb332d355a0bba15ddfaf3de..055325056a74aa7769d658b459f4840d7ffa328c 100644 (file)
--- a/arch/i386/kernel/i386_ksyms.c
+++ b/arch/i386/kernel/i386_ksyms.c
@@ -3,8 +3,6 @@
 #include <asm/checksum.h>
 #include <asm/desc.h>
 
-EXPORT_SYMBOL_GPL(cpu_gdt_descr);
-
 EXPORT_SYMBOL(__down_failed);
 EXPORT_SYMBOL(__down_failed_interruptible);
 EXPORT_SYMBOL(__down_failed_trylock);

diff --git a/arch/i386/kernel/smpboot.c b/arch/i386/kernel/smpboot.c
index fb00ab7b7612821e0c273df1d8f7f98b9a2aafb1..eba7f53f8b4a687c061601ea351943038a163c91 100644 (file)
--- a/arch/i386/kernel/smpboot.c
+++ b/arch/i386/kernel/smpboot.c
@@ -898,12 +898,6 @@ static int __devinit do_boot_cpu(int apicid, int cpu)
        unsigned long start_eip;
        unsigned short nmi_high = 0, nmi_low = 0;
 
-       if (!cpu_gdt_descr[cpu].address &&
-           !(cpu_gdt_descr[cpu].address = get_zeroed_page(GFP_KERNEL))) {
-               printk("Failed to allocate GDT for CPU %d\n", cpu);
-               return 1;
-       }
-
        ++cpucount;
 
        /*

diff --git a/include/asm-i386/desc.h b/include/asm-i386/desc.h
index 494e73bca0956c2f327e0eaf07e1cb83752cf3bb..89b8b82c82b30bb50695a3d1e63e38324444d31f 100644 (file)
--- a/include/asm-i386/desc.h
+++ b/include/asm-i386/desc.h
@@ -24,11 +24,13 @@ struct Xgt_desc_struct {
        unsigned short pad;
 } __attribute__ ((packed));
 
-extern struct Xgt_desc_struct idt_descr, cpu_gdt_descr[NR_CPUS];
+extern struct Xgt_desc_struct idt_descr;
+DECLARE_PER_CPU(struct Xgt_desc_struct, cpu_gdt_descr);
+
 
 static inline struct desc_struct *get_cpu_gdt_table(unsigned int cpu)
 {
-       return ((struct desc_struct *)cpu_gdt_descr[cpu].address);
+       return (struct desc_struct *)per_cpu(cpu_gdt_descr, cpu).address;
 }
 
 #define load_TR_desc() __asm__ __volatile__("ltr %w0"::"q" (GDT_ENTRY_TSS*8))