Currently, we have 3 GDT tables: one for early boot (boot_gdt_table),
one for late boot (cpu_gdt_table), and a dynamically-allocated per-cpu
one (per-cpu cpu_gdt_table *).
Simplify this and reduce waste, by using the per-cpu GDT table
directly in boot. This is done by using the table in the per-cpu
section until cpu_init() where the per-cpu copies have been set up.
This means we it's easier to define the cpu_gdt_table in C, otherwise
we'd need asm per-cpu definition macros.
Signed-off-by: Rusty Russell <[email protected]>
Index: ak-pda-gs/arch/i386/kernel/setup.c
===================================================================
--- ak-pda-gs.orig/arch/i386/kernel/setup.c 2006-09-20 15:38:27.000000000 +1000
+++ ak-pda-gs/arch/i386/kernel/setup.c 2006-09-20 15:39:01.000000000 +1000
@@ -1437,6 +1437,50 @@
tsc_init();
}
+/*
+ * The Global Descriptor Table contains 28 quadwords, per-CPU.
+ */
+__attribute__((aligned(L1_CACHE_BYTES)))
+DEFINE_PER_CPU(struct desc_struct, cpu_gdt_table[GDT_ENTRIES]) =
+{
+ /* kernel 4GB code at 0x00000000 */
+ [GDT_ENTRY_KERNEL_CS] = { 0x0000ffff, 0x00cf9a00 },
+ /* kernel 4GB data at 0x00000000 */
+ [GDT_ENTRY_KERNEL_DS] = { 0x0000ffff, 0x00cf9200 },
+ /* user 4GB code at 0x00000000 */
+ [GDT_ENTRY_DEFAULT_USER_CS] = { 0x0000ffff, 0x00cffa00 },
+ /* user 4GB data at 0x00000000 */
+ [GDT_ENTRY_DEFAULT_USER_DS] = { 0x0000ffff, 0x00cff200 },
+ /*
+ * Segments used for calling PnP BIOS have byte granularity.
+ * They code segments and data segments have fixed 64k limits,
+ * the transfer segment sizes are set at run time.
+ */
+ [GDT_ENTRY_PNPBIOS_BASE] =
+ { 0x0000ffff, 0x00409a00 }, /* 32-bit code */
+ { 0x0000ffff, 0x00009a00 }, /* 16-bit code */
+ { 0x0000ffff, 0x00009200 }, /* 16-bit data */
+ { 0x00000000, 0x00009200 }, /* 16-bit data */
+ { 0x00000000, 0x00009200 }, /* 16-bit data */
+
+ /*
+ * The APM segments have byte granularity and their bases
+ * are set at run time. All have 64k limits.
+ */
+ [GDT_ENTRY_APMBIOS_BASE] =
+ { 0x0000ffff, 0x00409a00 }, /* APM CS code */
+ { 0x0000ffff, 0x00009a00 }, /* APM CS 16 code (16 bit) */
+ { 0x0000ffff, 0x00409200 }, /* APM DS data */
+
+ /* ESPFIX 16-bit SS */
+ [GDT_ENTRY_ESPFIX_SS] = { 0x00000000, 0x00009200 },
+};
+
+/* Early in boot we use the master per-cpu gdt_table directly. */
+DEFINE_PER_CPU(struct Xgt_desc_struct, cpu_gdt_descr)
+= { .size = GDT_ENTRIES*8-1, .address = (long)&per_cpu__cpu_gdt_table };
+EXPORT_PER_CPU_SYMBOL(cpu_gdt_descr);
+
static __init int add_pcspkr(void)
{
struct platform_device *pd;
Index: ak-pda-gs/arch/i386/kernel/cpu/common.c
===================================================================
--- ak-pda-gs.orig/arch/i386/kernel/cpu/common.c 2006-09-20 15:38:27.000000000 +1000
+++ ak-pda-gs/arch/i386/kernel/cpu/common.c 2006-09-20 15:39:01.000000000 +1000
@@ -21,9 +21,6 @@
#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);
@@ -612,38 +609,8 @@
set_in_cr4(X86_CR4_TSD);
}
- /* The CPU hotplug case */
- if (cpu_gdt_descr->address) {
- gdt = (struct desc_struct *)cpu_gdt_descr->address;
- memset(gdt, 0, PAGE_SIZE);
- goto old_gdt;
- }
- /*
- * 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();
- }
- }
-old_gdt:
- /*
- * Initialize the per-CPU GDT with the boot GDT,
- * and set up the GDT descriptor:
- */
- memcpy(gdt, cpu_gdt_table, GDT_SIZE);
-
/* Set up GDT entry for 16bit stack */
+ gdt = __get_cpu_var(cpu_gdt_table);
*(__u64 *)(&gdt[GDT_ENTRY_ESPFIX_SS]) |=
((((__u64)stk16_off) << 16) & 0x000000ffffff0000ULL) |
((((__u64)stk16_off) << 32) & 0xff00000000000000ULL) |
Index: ak-pda-gs/arch/i386/kernel/head.S
===================================================================
--- ak-pda-gs.orig/arch/i386/kernel/head.S 2006-09-20 15:38:27.000000000 +1000
+++ ak-pda-gs/arch/i386/kernel/head.S 2006-09-20 15:39:01.000000000 +1000
@@ -302,7 +302,7 @@
movl %eax,%cr0
call check_x87
- lgdt cpu_gdt_descr
+ lgdt per_cpu__cpu_gdt_descr
lidt idt_descr
ljmp $(__KERNEL_CS),$1f
1: movl $(__KERNEL_DS),%eax # reload all the segment registers
@@ -456,12 +456,6 @@
.word IDT_ENTRIES*8-1 # idt contains 256 entries
.long idt_table
-# boot GDT descriptor (later on used by CPU#0):
- .word 0 # 32 bit align gdt_desc.address
-cpu_gdt_descr:
- .word GDT_ENTRIES*8-1
- .long cpu_gdt_table
-
/*
* The boot_gdt_table must mirror the equivalent in setup.S and is
* used only for booting.
@@ -472,55 +466,3 @@
.quad 0x00cf9a000000ffff /* kernel 4GB code at 0x00000000 */
.quad 0x00cf92000000ffff /* kernel 4GB data at 0x00000000 */
-/*
- * The Global Descriptor Table contains 28 quadwords, per-CPU.
- */
- .align L1_CACHE_BYTES
-ENTRY(cpu_gdt_table)
- .quad 0x0000000000000000 /* NULL descriptor */
- .quad 0x0000000000000000 /* 0x0b reserved */
- .quad 0x0000000000000000 /* 0x13 reserved */
- .quad 0x0000000000000000 /* 0x1b reserved */
- .quad 0x0000000000000000 /* 0x20 unused */
- .quad 0x0000000000000000 /* 0x28 unused */
- .quad 0x0000000000000000 /* 0x33 TLS entry 1 */
- .quad 0x0000000000000000 /* 0x3b TLS entry 2 */
- .quad 0x0000000000000000 /* 0x43 TLS entry 3 */
- .quad 0x0000000000000000 /* 0x4b reserved */
- .quad 0x0000000000000000 /* 0x53 reserved */
- .quad 0x0000000000000000 /* 0x5b reserved */
-
- .quad 0x00cf9a000000ffff /* 0x60 kernel 4GB code at 0x00000000 */
- .quad 0x00cf92000000ffff /* 0x68 kernel 4GB data at 0x00000000 */
- .quad 0x00cffa000000ffff /* 0x73 user 4GB code at 0x00000000 */
- .quad 0x00cff2000000ffff /* 0x7b user 4GB data at 0x00000000 */
-
- .quad 0x0000000000000000 /* 0x80 TSS descriptor */
- .quad 0x0000000000000000 /* 0x88 LDT descriptor */
-
- /*
- * Segments used for calling PnP BIOS have byte granularity.
- * They code segments and data segments have fixed 64k limits,
- * the transfer segment sizes are set at run time.
- */
- .quad 0x00409a000000ffff /* 0x90 32-bit code */
- .quad 0x00009a000000ffff /* 0x98 16-bit code */
- .quad 0x000092000000ffff /* 0xa0 16-bit data */
- .quad 0x0000920000000000 /* 0xa8 16-bit data */
- .quad 0x0000920000000000 /* 0xb0 16-bit data */
-
- /*
- * The APM segments have byte granularity and their bases
- * are set at run time. All have 64k limits.
- */
- .quad 0x00409a000000ffff /* 0xb8 APM CS code */
- .quad 0x00009a000000ffff /* 0xc0 APM CS 16 code (16 bit) */
- .quad 0x004092000000ffff /* 0xc8 APM DS data */
-
- .quad 0x0000920000000000 /* 0xd0 - ESPFIX 16-bit SS */
- .quad 0x0000000000000000 /* 0xd8 - unused */
- .quad 0x0000000000000000 /* 0xe0 - unused */
- .quad 0x0000000000000000 /* 0xe8 - unused */
- .quad 0x0000000000000000 /* 0xf0 - unused */
- .quad 0x0000000000000000 /* 0xf8 - GDT entry 31: double-fault TSS */
-
Index: ak-pda-gs/arch/i386/kernel/smpboot.c
===================================================================
--- ak-pda-gs.orig/arch/i386/kernel/smpboot.c 2006-09-20 15:38:27.000000000 +1000
+++ ak-pda-gs/arch/i386/kernel/smpboot.c 2006-09-20 15:39:01.000000000 +1000
@@ -1058,7 +1058,6 @@
struct warm_boot_cpu_info info;
struct work_struct task;
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) {
@@ -1066,18 +1065,6 @@
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;
Index: ak-pda-gs/include/asm-i386/desc.h
===================================================================
--- ak-pda-gs.orig/include/asm-i386/desc.h 2006-09-20 15:27:51.000000000 +1000
+++ ak-pda-gs/include/asm-i386/desc.h 2006-09-20 15:39:01.000000000 +1000
@@ -14,8 +14,7 @@
#include <asm/mmu.h>
-extern struct desc_struct cpu_gdt_table[GDT_ENTRIES];
-
+DECLARE_PER_CPU(struct desc_struct, cpu_gdt_table[GDT_ENTRIES]);
DECLARE_PER_CPU(unsigned char, cpu_16bit_stack[CPU_16BIT_STACK_SIZE]);
struct Xgt_desc_struct {
--
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