i386: Use per-cpu variables for GDT, PDA From: Rusty Russell 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 Signed-off-by: Andi Kleen Cc: Andi Kleen Signed-off-by: Andrew Morton --- arch/i386/kernel/cpu/common.c | 94 ++++------------------------------- arch/i386/kernel/smpboot.c | 21 ------- arch/i386/mach-voyager/voyager_smp.c | 10 --- include/asm-generic/percpu.h | 1 include/asm-i386/desc.h | 1 include/asm-i386/pda.h | 7 +- include/asm-i386/processor.h | 2 7 files changed, 21 insertions(+), 115 deletions(-) Index: linux/arch/i386/kernel/cpu/common.c =================================================================== --- linux.orig/arch/i386/kernel/cpu/common.c +++ linux/arch/i386/kernel/cpu/common.c @@ -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(str 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); - - BUG_ON(gdt == NULL || pda == NULL); + struct desc_struct *gdt = per_cpu(cpu_gdt, cpu); + struct i386_pda *pda = &per_cpu(_cpu_pda, cpu); - /* - * 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 t 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); } Index: linux/arch/i386/kernel/smpboot.c =================================================================== --- linux.orig/arch/i386/kernel/smpboot.c +++ linux/arch/i386/kernel/smpboot.c @@ -808,13 +808,7 @@ static int __cpuinit do_boot_cpu(int api 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(i 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(i 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: linux/arch/i386/mach-voyager/voyager_smp.c =================================================================== --- linux.orig/arch/i386/mach-voyager/voyager_smp.c +++ linux/arch/i386/mach-voyager/voyager_smp.c @@ -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 */ Index: linux/include/asm-generic/percpu.h =================================================================== --- linux.orig/include/asm-generic/percpu.h +++ linux/include/asm-generic/percpu.h @@ -1,6 +1,7 @@ #ifndef _ASM_GENERIC_PERCPU_H_ #define _ASM_GENERIC_PERCPU_H_ #include +#include #define __GENERIC_PER_CPU #ifdef CONFIG_SMP Index: linux/include/asm-i386/desc.h =================================================================== --- linux.orig/include/asm-i386/desc.h +++ linux/include/asm-i386/desc.h @@ -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) Index: linux/include/asm-i386/pda.h =================================================================== --- linux.orig/include/asm-i386/pda.h +++ linux/include/asm-i386/pda.h @@ -8,6 +8,7 @@ #include #include +#include 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); Index: linux/include/asm-i386/processor.h =================================================================== --- linux.orig/include/asm-i386/processor.h +++ linux/include/asm-i386/processor.h @@ -743,7 +743,7 @@ extern unsigned long boot_option_idle_ov 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);