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Commit ae1ee11b authored by Rusty Russell's avatar Rusty Russell Committed by Andi Kleen
Browse files

[PATCH] i386: Use per-cpu variables for GDT, PDA 



Allocating PDA and GDT at boot is a pain.  Using simple per-cpu variables adds
happiness (although we need the GDT page-aligned for Xen, which we do in a
followup patch).

[akpm@linux-foundation.org: build fix]
Signed-off-by: default avatarRusty Russell <rusty@rustcorp.com.au>
Signed-off-by: default avatarAndi Kleen <ak@suse.de>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 8f9aeca7

arch/i386/kernel/cpu/common.c

+13 −81
Original line number Diff line number Diff line
@@ -25,8 +25,10 @@ 
DEFINE_PER_CPU(struct Xgt_desc_struct, cpu_gdt_descr);

EXPORT_PER_CPU_SYMBOL(cpu_gdt_descr);



struct i386_pda *_cpu_pda[NR_CPUS] __read_mostly;

EXPORT_SYMBOL(_cpu_pda);

DEFINE_PER_CPU(struct desc_struct, cpu_gdt[GDT_ENTRIES]);



DEFINE_PER_CPU(struct i386_pda, _cpu_pda);

EXPORT_PER_CPU_SYMBOL(_cpu_pda);



static int cachesize_override __cpuinitdata = -1;

static int disable_x86_fxsr __cpuinitdata;
@@ -609,52 +611,6 @@ struct pt_regs * __devinit idle_regs(struct pt_regs *regs) 
	return regs;

}



static __cpuinit int alloc_gdt(int cpu)

{

	struct Xgt_desc_struct *cpu_gdt_descr = &per_cpu(cpu_gdt_descr, cpu);

	struct desc_struct *gdt;

	struct i386_pda *pda;



	gdt = (struct desc_struct *)cpu_gdt_descr->address;

	pda = cpu_pda(cpu);



	/*

	 * 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) {

		BUG_ON(gdt != NULL || pda != NULL);



		gdt = alloc_bootmem_pages(PAGE_SIZE);

		pda = alloc_bootmem(sizeof(*pda));

		/* alloc_bootmem(_pages) panics on failure, so no check */



		memset(gdt, 0, PAGE_SIZE);

		memset(pda, 0, sizeof(*pda));

	} else {

		/* GDT and PDA might already have been allocated if

		   this is a CPU hotplug re-insertion. */

		if (gdt == NULL)

			gdt = (struct desc_struct *)get_zeroed_page(GFP_KERNEL);



		if (pda == NULL)

			pda = kmalloc_node(sizeof(*pda), GFP_KERNEL, cpu_to_node(cpu));



		if (unlikely(!gdt || !pda)) {

			free_pages((unsigned long)gdt, 0);

			kfree(pda);

			return 0;

		}

	}



 	cpu_gdt_descr->address = (unsigned long)gdt;

	cpu_pda(cpu) = pda;



	return 1;

}



/* Initial PDA used by boot CPU */

struct i386_pda boot_pda = {

	._pda = &boot_pda,
@@ -670,31 +626,17 @@ static inline void set_kernel_fs(void) 
	asm volatile ("mov %0, %%fs" : : "r" (__KERNEL_PDA) : "memory");

}



/* Initialize the CPU's GDT and PDA.  The boot CPU does this for

   itself, but secondaries find this done for them. */

__cpuinit int init_gdt(int cpu, struct task_struct *idle)

/* Initialize the CPU's GDT and PDA.  This is either the boot CPU doing itself

   (still using cpu_gdt_table), or a CPU doing it for a secondary which

   will soon come up. */

__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;

	struct i386_pda *pda;



	/* For non-boot CPUs, the GDT and PDA should already have been

	   allocated. */

	if (!alloc_gdt(cpu)) {

		printk(KERN_CRIT "CPU%d failed to allocate GDT or PDA\n", cpu);

		return 0;

	}



	gdt = (struct desc_struct *)cpu_gdt_descr->address;

	pda = cpu_pda(cpu);

	struct desc_struct *gdt = per_cpu(cpu_gdt, cpu);

	struct i386_pda *pda = &per_cpu(_cpu_pda, cpu);



	BUG_ON(gdt == NULL || pda == NULL);



	/*

	 * Initialize the per-CPU GDT with the boot GDT,

	 * and set up the GDT descriptor:

	 */

 	memcpy(gdt, cpu_gdt_table, GDT_SIZE);

 	cpu_gdt_descr->address = (unsigned long)gdt;

	cpu_gdt_descr->size = GDT_SIZE - 1;



	pack_descriptor((u32 *)&gdt[GDT_ENTRY_PDA].a,
@@ -706,17 +648,12 @@ __cpuinit int init_gdt(int cpu, struct task_struct *idle) 
	pda->_pda = pda;

	pda->cpu_number = cpu;

	pda->pcurrent = idle;



	return 1;

}



void __cpuinit cpu_set_gdt(int cpu)

{

	struct Xgt_desc_struct *cpu_gdt_descr = &per_cpu(cpu_gdt_descr, cpu);



	/* Reinit these anyway, even if they've already been done (on

	   the boot CPU, this will transition from the boot gdt+pda to

	   the real ones). */

	load_gdt(cpu_gdt_descr);

	set_kernel_fs();

}
@@ -804,13 +741,8 @@ void __cpuinit cpu_init(void) 
	struct task_struct *curr = current;



	/* Set up the real GDT and PDA, so we can transition from the

	   boot versions. */

	if (!init_gdt(cpu, curr)) {

		/* failed to allocate something; not much we can do... */

		for (;;)

			local_irq_enable();

	}



	   boot_gdt_table & boot_pda. */

	init_gdt(cpu, curr);

	cpu_set_gdt(cpu);

	_cpu_init(cpu, curr);

}

arch/i386/kernel/smpboot.c

+1 −20
Original line number Diff line number Diff line
@@ -808,13 +808,7 @@ static int __cpuinit do_boot_cpu(int apicid, int 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;	/* ? */

	}

	init_gdt(cpu, idle);



	idle->thread.eip = (unsigned long) start_secondary;

	/* start_eip had better be page-aligned! */
@@ -940,7 +934,6 @@ static int __cpuinit __smp_prepare_cpu(int cpu) 
	DECLARE_COMPLETION_ONSTACK(done);

	struct warm_boot_cpu_info info;

	int	apicid, ret;

	struct Xgt_desc_struct *cpu_gdt_descr = &per_cpu(cpu_gdt_descr, cpu);



	apicid = x86_cpu_to_apicid[cpu];

	if (apicid == BAD_APICID) {
@@ -948,18 +941,6 @@ static int __cpuinit __smp_prepare_cpu(int cpu) 
		goto exit;

	}



	/*

	 * the CPU isn't initialized at boot time, allocate gdt table here.

	 * cpu_init will initialize it

	 */

	if (!cpu_gdt_descr->address) {

		cpu_gdt_descr->address = get_zeroed_page(GFP_KERNEL);

		if (!cpu_gdt_descr->address)

			printk(KERN_CRIT "CPU%d failed to allocate GDT\n", cpu);

			ret = -ENOMEM;

			goto exit;

	}



	info.complete = &done;

	info.apicid = apicid;

	info.cpu = cpu;

arch/i386/mach-voyager/voyager_smp.c

+1 −9
Original line number Diff line number Diff line
@@ -580,15 +580,7 @@ do_boot_cpu(__u8 cpu) 
	/* init_tasks (in sched.c) is indexed logically */

	stack_start.esp = (void *) idle->thread.esp;



	/* 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);

		cpucount--;

		return;

	}



	init_gdt(cpu, idle);

	irq_ctx_init(cpu);



	/* Note: Don't modify initial ss override */

include/asm-generic/percpu.h

+1 −0
Original line number Diff line number Diff line 
#ifndef _ASM_GENERIC_PERCPU_H_

#define _ASM_GENERIC_PERCPU_H_

#include <linux/compiler.h>

#include <linux/threads.h>



#define __GENERIC_PER_CPU

#ifdef CONFIG_SMP

include/asm-i386/desc.h

+1 −0
Original line number Diff line number Diff line
@@ -22,6 +22,7 @@ struct Xgt_desc_struct { 


extern struct Xgt_desc_struct idt_descr;

DECLARE_PER_CPU(struct Xgt_desc_struct, cpu_gdt_descr);

DECLARE_PER_CPU(struct desc_struct, cpu_gdt[GDT_ENTRIES]);

extern struct Xgt_desc_struct early_gdt_descr;



static inline struct desc_struct *get_cpu_gdt_table(unsigned int cpu)