[PATCH] i386: Use per-cpu GDT immediately upon boot
Now we are no longer dynamically allocating the GDT, we don't need the "cpu_gdt_table" at all: we can switch straight from "boot_gdt_table" to the per-cpu GDT. This means initializing the cpu_gdt array in C. The boot CPU uses the per-cpu var directly, then in smp_prepare_cpus() it switches to the per-cpu copy just allocated. For secondary CPUs, the early_gdt_descr is set to point directly to their per-cpu copy. For UP the code is very simple: it keeps using the "per-cpu" GDT as per SMP, but we never have to move. 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>
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@ -25,7 +25,33 @@
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DEFINE_PER_CPU(struct Xgt_desc_struct, cpu_gdt_descr);
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EXPORT_PER_CPU_SYMBOL(cpu_gdt_descr);
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DEFINE_PER_CPU(struct desc_struct, cpu_gdt[GDT_ENTRIES]);
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DEFINE_PER_CPU(struct desc_struct, cpu_gdt[GDT_ENTRIES]) = {
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[GDT_ENTRY_KERNEL_CS] = { 0x0000ffff, 0x00cf9a00 },
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[GDT_ENTRY_KERNEL_DS] = { 0x0000ffff, 0x00cf9200 },
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[GDT_ENTRY_DEFAULT_USER_CS] = { 0x0000ffff, 0x00cffa00 },
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[GDT_ENTRY_DEFAULT_USER_DS] = { 0x0000ffff, 0x00cff200 },
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/*
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* Segments used for calling PnP BIOS have byte granularity.
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* They code segments and data segments have fixed 64k limits,
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* the transfer segment sizes are set at run time.
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*/
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[GDT_ENTRY_PNPBIOS_CS32] = { 0x0000ffff, 0x00409a00 },/* 32-bit code */
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[GDT_ENTRY_PNPBIOS_CS16] = { 0x0000ffff, 0x00009a00 },/* 16-bit code */
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[GDT_ENTRY_PNPBIOS_DS] = { 0x0000ffff, 0x00009200 }, /* 16-bit data */
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[GDT_ENTRY_PNPBIOS_TS1] = { 0x00000000, 0x00009200 },/* 16-bit data */
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[GDT_ENTRY_PNPBIOS_TS2] = { 0x00000000, 0x00009200 },/* 16-bit data */
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/*
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* The APM segments have byte granularity and their bases
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* are set at run time. All have 64k limits.
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*/
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[GDT_ENTRY_APMBIOS_BASE] = { 0x0000ffff, 0x00409a00 },/* 32-bit code */
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/* 16-bit code */
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[GDT_ENTRY_APMBIOS_BASE+1] = { 0x0000ffff, 0x00009a00 },
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[GDT_ENTRY_APMBIOS_BASE+2] = { 0x0000ffff, 0x00409200 }, /* data */
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[GDT_ENTRY_ESPFIX_SS] = { 0x00000000, 0x00c09200 },
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[GDT_ENTRY_PDA] = { 0x00000000, 0x00c09200 }, /* set in setup_pda */
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};
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DEFINE_PER_CPU(struct i386_pda, _cpu_pda);
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EXPORT_PER_CPU_SYMBOL(_cpu_pda);
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@ -618,46 +644,6 @@ struct i386_pda boot_pda = {
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.pcurrent = &init_task,
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};
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static inline void set_kernel_fs(void)
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{
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/* Set %fs for this CPU's PDA. Memory clobber is to create a
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barrier with respect to any PDA operations, so the compiler
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doesn't move any before here. */
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asm volatile ("mov %0, %%fs" : : "r" (__KERNEL_PDA) : "memory");
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}
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/* Initialize the CPU's GDT and PDA. This is either the boot CPU doing itself
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(still using cpu_gdt_table), or a CPU doing it for a secondary which
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will soon come up. */
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__cpuinit void init_gdt(int cpu, struct task_struct *idle)
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{
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struct Xgt_desc_struct *cpu_gdt_descr = &per_cpu(cpu_gdt_descr, cpu);
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struct desc_struct *gdt = per_cpu(cpu_gdt, cpu);
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struct i386_pda *pda = &per_cpu(_cpu_pda, cpu);
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memcpy(gdt, cpu_gdt_table, GDT_SIZE);
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cpu_gdt_descr->address = (unsigned long)gdt;
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cpu_gdt_descr->size = GDT_SIZE - 1;
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pack_descriptor((u32 *)&gdt[GDT_ENTRY_PDA].a,
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(u32 *)&gdt[GDT_ENTRY_PDA].b,
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(unsigned long)pda, sizeof(*pda) - 1,
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0x80 | DESCTYPE_S | 0x2, 0); /* present read-write data segment */
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memset(pda, 0, sizeof(*pda));
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pda->_pda = pda;
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pda->cpu_number = cpu;
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pda->pcurrent = idle;
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}
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void __cpuinit cpu_set_gdt(int cpu)
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{
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struct Xgt_desc_struct *cpu_gdt_descr = &per_cpu(cpu_gdt_descr, cpu);
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load_gdt(cpu_gdt_descr);
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set_kernel_fs();
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}
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/* Common CPU init for both boot and secondary CPUs */
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static void __cpuinit _cpu_init(int cpu, struct task_struct *curr)
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{
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@ -740,10 +726,6 @@ void __cpuinit cpu_init(void)
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int cpu = smp_processor_id();
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struct task_struct *curr = current;
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/* Set up the real GDT and PDA, so we can transition from the
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boot_gdt_table & boot_pda. */
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init_gdt(cpu, curr);
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cpu_set_gdt(cpu);
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_cpu_init(cpu, curr);
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}
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@ -599,7 +599,7 @@ idt_descr:
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.word 0 # 32 bit align gdt_desc.address
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ENTRY(early_gdt_descr)
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.word GDT_ENTRIES*8-1
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.long cpu_gdt_table
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.long per_cpu__cpu_gdt /* Overwritten for secondary CPUs */
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/*
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* The boot_gdt_table must mirror the equivalent in setup.S and is
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@ -610,56 +610,3 @@ ENTRY(boot_gdt_table)
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.fill GDT_ENTRY_BOOT_CS,8,0
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.quad 0x00cf9a000000ffff /* kernel 4GB code at 0x00000000 */
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.quad 0x00cf92000000ffff /* kernel 4GB data at 0x00000000 */
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/*
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* The Global Descriptor Table contains 32 quadwords, per-CPU.
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*/
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.align L1_CACHE_BYTES
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ENTRY(cpu_gdt_table)
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.quad 0x0000000000000000 /* NULL descriptor */
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.quad 0x0000000000000000 /* 0x0b reserved */
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.quad 0x0000000000000000 /* 0x13 reserved */
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.quad 0x0000000000000000 /* 0x1b reserved */
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.quad 0x0000000000000000 /* 0x20 unused */
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.quad 0x0000000000000000 /* 0x28 unused */
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.quad 0x0000000000000000 /* 0x33 TLS entry 1 */
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.quad 0x0000000000000000 /* 0x3b TLS entry 2 */
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.quad 0x0000000000000000 /* 0x43 TLS entry 3 */
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.quad 0x0000000000000000 /* 0x4b reserved */
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.quad 0x0000000000000000 /* 0x53 reserved */
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.quad 0x0000000000000000 /* 0x5b reserved */
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.quad 0x00cf9a000000ffff /* 0x60 kernel 4GB code at 0x00000000 */
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.quad 0x00cf92000000ffff /* 0x68 kernel 4GB data at 0x00000000 */
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.quad 0x00cffa000000ffff /* 0x73 user 4GB code at 0x00000000 */
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.quad 0x00cff2000000ffff /* 0x7b user 4GB data at 0x00000000 */
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.quad 0x0000000000000000 /* 0x80 TSS descriptor */
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.quad 0x0000000000000000 /* 0x88 LDT descriptor */
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/*
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* Segments used for calling PnP BIOS have byte granularity.
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* The code segments and data segments have fixed 64k limits,
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* the transfer segment sizes are set at run time.
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*/
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.quad 0x00409a000000ffff /* 0x90 32-bit code */
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.quad 0x00009a000000ffff /* 0x98 16-bit code */
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.quad 0x000092000000ffff /* 0xa0 16-bit data */
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.quad 0x0000920000000000 /* 0xa8 16-bit data */
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.quad 0x0000920000000000 /* 0xb0 16-bit data */
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/*
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* The APM segments have byte granularity and their bases
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* are set at run time. All have 64k limits.
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*/
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.quad 0x00409a000000ffff /* 0xb8 APM CS code */
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.quad 0x00009a000000ffff /* 0xc0 APM CS 16 code (16 bit) */
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.quad 0x004092000000ffff /* 0xc8 APM DS data */
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.quad 0x00c0920000000000 /* 0xd0 - ESPFIX SS */
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.quad 0x00cf92000000ffff /* 0xd8 - PDA */
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.quad 0x0000000000000000 /* 0xe0 - unused */
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.quad 0x0000000000000000 /* 0xe8 - unused */
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.quad 0x0000000000000000 /* 0xf0 - unused */
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.quad 0x0000000000000000 /* 0xf8 - GDT entry 31: double-fault TSS */
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@ -439,12 +439,6 @@ static void __cpuinit start_secondary(void *unused)
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*/
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void __devinit initialize_secondary(void)
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{
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/*
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* switch to the per CPU GDT we already set up
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* in do_boot_cpu()
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*/
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cpu_set_gdt(current_thread_info()->cpu);
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/*
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* We don't actually need to load the full TSS,
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* basically just the stack pointer and the eip.
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@ -787,6 +781,32 @@ static inline struct task_struct * alloc_idle_task(int cpu)
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#define alloc_idle_task(cpu) fork_idle(cpu)
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#endif
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/* Initialize the CPU's GDT. This is either the boot CPU doing itself
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(still using the master per-cpu area), or a CPU doing it for a
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secondary which will soon come up. */
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static __cpuinit void init_gdt(int cpu, struct task_struct *idle)
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{
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struct Xgt_desc_struct *cpu_gdt_descr = &per_cpu(cpu_gdt_descr, cpu);
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struct desc_struct *gdt = per_cpu(cpu_gdt, cpu);
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struct i386_pda *pda = &per_cpu(_cpu_pda, cpu);
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cpu_gdt_descr->address = (unsigned long)gdt;
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cpu_gdt_descr->size = GDT_SIZE - 1;
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pack_descriptor((u32 *)&gdt[GDT_ENTRY_PDA].a,
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(u32 *)&gdt[GDT_ENTRY_PDA].b,
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(unsigned long)pda, sizeof(*pda) - 1,
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0x80 | DESCTYPE_S | 0x2, 0); /* present read-write data segment */
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memset(pda, 0, sizeof(*pda));
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pda->_pda = pda;
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pda->cpu_number = cpu;
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pda->pcurrent = idle;
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}
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/* Defined in head.S */
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extern struct Xgt_desc_struct early_gdt_descr;
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static int __cpuinit do_boot_cpu(int apicid, int cpu)
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/*
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* NOTE - on most systems this is a PHYSICAL apic ID, but on multiquad
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panic("failed fork for CPU %d", cpu);
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init_gdt(cpu, idle);
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early_gdt_descr.address = (unsigned long)get_cpu_gdt_table(cpu);
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start_pda = cpu_pda(cpu);
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idle->thread.eip = (unsigned long) start_secondary;
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/* start_eip had better be page-aligned! */
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@ -1161,13 +1183,26 @@ void __init smp_prepare_cpus(unsigned int max_cpus)
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smp_boot_cpus(max_cpus);
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}
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void __devinit smp_prepare_boot_cpu(void)
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/* Current gdt points %fs at the "master" per-cpu area: after this,
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* it's on the real one. */
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static inline void switch_to_new_gdt(void)
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{
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cpu_set(smp_processor_id(), cpu_online_map);
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cpu_set(smp_processor_id(), cpu_callout_map);
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cpu_set(smp_processor_id(), cpu_present_map);
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cpu_set(smp_processor_id(), cpu_possible_map);
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per_cpu(cpu_state, smp_processor_id()) = CPU_ONLINE;
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load_gdt(&per_cpu(cpu_gdt_descr, smp_processor_id()));
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asm volatile ("mov %0, %%fs" : : "r" (__KERNEL_PDA) : "memory");
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}
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void __init smp_prepare_boot_cpu(void)
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{
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unsigned int cpu = smp_processor_id();
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init_gdt(cpu, current);
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switch_to_new_gdt();
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cpu_set(cpu, cpu_online_map);
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cpu_set(cpu, cpu_callout_map);
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cpu_set(cpu, cpu_present_map);
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cpu_set(cpu, cpu_possible_map);
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__get_cpu_var(cpu_state) = CPU_ONLINE;
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}
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#ifdef CONFIG_HOTPLUG_CPU
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@ -764,12 +764,6 @@ initialize_secondary(void)
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set_current(hard_get_current());
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#endif
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/*
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* switch to the per CPU GDT we already set up
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* in do_boot_cpu()
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*/
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cpu_set_gdt(current_thread_info()->cpu);
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/*
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* We don't actually need to load the full TSS,
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* basically just the stack pointer and the eip.
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@ -12,8 +12,6 @@
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#include <asm/mmu.h>
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extern struct desc_struct cpu_gdt_table[GDT_ENTRIES];
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struct Xgt_desc_struct {
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unsigned short size;
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unsigned long address __attribute__((packed));
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@ -743,7 +743,6 @@ extern unsigned long boot_option_idle_override;
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extern void enable_sep_cpu(void);
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extern int sysenter_setup(void);
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extern void init_gdt(int cpu, struct task_struct *idle);
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extern void cpu_set_gdt(int);
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extern void secondary_cpu_init(void);
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