[PATCH RFC 2/6] Initialize the per-CPU data area.

Jeremy Fitzhardinge
2006-08-27T09:25:58Z

[-- Attachment #1: i386-pda-init.patch --]
[-- Type: text/plain, Size: 3578 bytes --]

When a CPU is brought up, a PDA and GDT are allocated for it. The
GDT's __KERNEL_PDA entry is pointed to the allocated PDA memory, so
that all references using this segment selector will refer to the PDA.

Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com>
Cc: Chuck Ebbert <76306.1226@compuserve.com>
Cc: Zachary Amsden <zach@vmware.com>
Cc: Jan Beulich <jbeulich@novell.com>
Cc: Andi Kleen <ak@suse.de>

---
arch/i386/kernel/cpu/common.c | 49 ++++++++++++++++++++++++++++++++++++++---
1 file changed, 46 insertions(+), 3 deletions(-)

===================================================================
--- a/arch/i386/kernel/cpu/common.c
+++ b/arch/i386/kernel/cpu/common.c
@@ -18,6 +18,7 @@
#include <asm/apic.h>
#include <mach_apic.h>
#endif
+#include <asm/pda.h>

#include "cpu.h"

@@ -26,6 +27,9 @@ 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);
+
+struct i386_pda *_cpu_pda[NR_CPUS] __read_mostly;
+EXPORT_SYMBOL(_cpu_pda);

static int cachesize_override __cpuinitdata = -1;
static int disable_x86_fxsr __cpuinitdata;
@@ -582,6 +586,26 @@ void __init early_cpu_init(void)
disable_pse = 1;
#endif
}
+
+static __cpuinit void pda_init(int cpu)
+{
+ struct i386_pda *pda = cpu_pda(cpu);
+
+ memset(pda, 0, sizeof(*pda));
+
+ pda->cpu_number = cpu;
+ pda->pcurrent = current;
+
+ printk("cpu %d current %p\n", cpu, current);
+}
+
+struct pt_regs * __devinit idle_regs(struct pt_regs *regs)
+{
+ memset(regs, 0, sizeof(struct pt_regs));
+ regs->xgs = __KERNEL_PDA;
+ return regs;
+}
+
/*
* cpu_init() initializes state that is per-CPU. Some data is already
* initialized (naturally) in the bootstrap process, such as the GDT
@@ -594,6 +618,7 @@ void __cpuinit cpu_init(void)
struct tss_struct * t = &per_cpu(init_tss, cpu);
struct thread_struct *thread = &current->thread;
struct desc_struct *gdt;
+ struct i386_pda *pda;
__u32 stk16_off = (__u32)&per_cpu(cpu_16bit_stack, cpu);
struct Xgt_desc_struct *cpu_gdt_descr = &per_cpu(cpu_gdt_descr, cpu);

@@ -615,6 +640,10 @@ void __cpuinit cpu_init(void)
/* The CPU hotplug case */
if (cpu_gdt_descr->address) {
gdt = (struct desc_struct *)cpu_gdt_descr->address;
+ pda = cpu_pda(cpu);
+
+ BUG_ON(pda == NULL);
+
memset(gdt, 0, PAGE_SIZE);
goto old_gdt;
}
@@ -625,13 +654,17 @@ void __cpuinit cpu_init(void)
* CPUs, when bootmem will have gone away
*/
if (NODE_DATA(0)->bdata->node_bootmem_map) {
- gdt = (struct desc_struct *)alloc_bootmem_pages(PAGE_SIZE);
+ 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);
} else {
gdt = (struct desc_struct *)get_zeroed_page(GFP_KERNEL);
- if (unlikely(!gdt)) {
- printk(KERN_CRIT "CPU%d failed to allocate GDT\n", cpu);
+ pda = kmalloc_node(sizeof(*pda), GFP_KERNEL, cpu_to_node(cpu));
+
+ if (unlikely(!gdt || !pda)) {
+ printk(KERN_CRIT "CPU%d failed to allocate GDT or PDA\n", cpu);
for (;;)
local_irq_enable();
}
@@ -651,6 +684,16 @@ old_gdt:

cpu_gdt_descr->size = GDT_SIZE - 1;
cpu_gdt_descr->address = (unsigned long)gdt;
+
+ /* Set up the PDA in this CPU's GDT */
+ cpu_pda(cpu) = pda;
+
+ pda_init(cpu);
+
+ pack_descriptor((u32 *)&gdt[GDT_ENTRY_PDA].a,
+ (u32 *)&gdt[GDT_ENTRY_PDA].b,
+ (unsigned long)pda, sizeof(*pda) - 1,
+ 0x80 | DESCTYPE_S | 0x2, 0); /* present read-write data segment */

load_gdt(cpu_gdt_descr);
load_idt(&idt_descr);

--