Commit 2b932f6c authored by James Bottomley's avatar James Bottomley Committed by Linus Torvalds
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[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: default avatarJames Bottomley <James.Bottomley@SteelEye.com>
Cc: Zachary Amsden <zach@vmware.com>
Cc: Matt Tolentino <metolent@snoqualmie.dp.intel.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 1e275d40

arch/i386/kernel/cpu/common.c

+28 −4
Original line number Diff line number Diff line
@@ -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);



	/*

arch/i386/kernel/efi.c

+7 −5
Original line number Diff line number Diff line
@@ -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) {

arch/i386/kernel/head.S

+0 −2
Original line number Diff line number Diff line
@@ -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

arch/i386/kernel/i386_ksyms.c

+0 −2
Original line number Diff line number Diff line
@@ -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);

arch/i386/kernel/smpboot.c

+0 −6
Original line number Diff line number Diff line
@@ -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;



	/*

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