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

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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: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Andi Kleen <ak@suse.de>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Rusty Russell 2007-05-02 19:27:10 +02:00 committed by Andi Kleen
parent 8f9aeca7a0
commit ae1ee11be7
7 changed files with 21 additions and 115 deletions
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94
arch/i386/kernel/cpu/common.c
View file

@ -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;
struct desc_struct *gdt = per_cpu(cpu_gdt, cpu);
struct i386_pda *pda = &per_cpu(_cpu_pda, cpu);
/* 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);
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);
}

21
arch/i386/kernel/smpboot.c
View file

@ -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;

10
arch/i386/mach-voyager/voyager_smp.c
View file

@ -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 */

1
include/asm-generic/percpu.h
View file

@ -1,6 +1,7 @@
#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

1
include/asm-i386/desc.h
View file

@ -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)

7
include/asm-i386/pda.h
View file

@ -8,6 +8,7 @@
#include <linux/stddef.h>
#include <linux/types.h>
#include <asm/percpu.h>
struct i386_pda
{
@ -18,10 +19,8 @@ struct i386_pda
struct pt_regs *irq_regs;
};
extern struct i386_pda *_cpu_pda[];
#define cpu_pda(i) (_cpu_pda[i])
DECLARE_PER_CPU(struct i386_pda, _cpu_pda);
#define cpu_pda(i) (&per_cpu(_cpu_pda, (i)))
#define pda_offset(field) offsetof(struct i386_pda, field)
extern void __bad_pda_field(void);

2
include/asm-i386/processor.h
View file

@ -743,7 +743,7 @@ extern unsigned long boot_option_idle_override;
extern void enable_sep_cpu(void);
extern int sysenter_setup(void);
extern int init_gdt(int cpu, struct task_struct *idle);
extern void init_gdt(int cpu, struct task_struct *idle);
extern void cpu_set_gdt(int);
extern void secondary_cpu_init(void);