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

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>

diff --git a/arch/i386/kernel/cpu/common.c b/arch/i386/kernel/cpu/common.c
index dcbbd0a8bfc2b8b5aa29ce1b7d4b1b78dd47b4e2..2335f4464eada9460f41ae1485e5090c16d2d6d1 100644 (file)
--- a/arch/i386/kernel/cpu/common.c
+++ b/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(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;
-
-       /* 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;
-       }
+       struct desc_struct *gdt = per_cpu(cpu_gdt, cpu);
+       struct i386_pda *pda = &per_cpu(_cpu_pda, cpu);
 
-       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);
 }

diff --git a/arch/i386/kernel/smpboot.c b/arch/i386/kernel/smpboot.c
index 7b14e88b555f6bde836aaebbd9644f22d829586d..b36a5f174cc9db09e0c85535dec466ad6e8cb6a9 100644 (file)
--- a/arch/i386/kernel/smpboot.c
+++ b/arch/i386/kernel/smpboot.c
@@ -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;

diff --git a/arch/i386/mach-voyager/voyager_smp.c b/arch/i386/mach-voyager/voyager_smp.c
index 74aeedf277f424896c1beaf01580468ecfbe90b5..15d8132d4f5e172c516966472afcb90cf4e58fec 100644 (file)
--- a/arch/i386/mach-voyager/voyager_smp.c
+++ b/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 */

diff --git a/include/asm-generic/percpu.h b/include/asm-generic/percpu.h
index 196376262240470ba6d5d3a11990e55690099629..d984a90414361b8f087cfcc83e8f15b3dcbe2989 100644 (file)
--- a/include/asm-generic/percpu.h
+++ b/include/asm-generic/percpu.h
@@ -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

diff --git a/include/asm-i386/desc.h b/include/asm-i386/desc.h
index 050831f34f71ce8f2001872c41b982c61262043e..53c5916687b6308837ec6b86506002d27e82bc83 100644 (file)
--- a/include/asm-i386/desc.h
+++ b/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)

diff --git a/include/asm-i386/pda.h b/include/asm-i386/pda.h
index b12d59a318b7cc46d581e347713e1964a4503ba7..aef7f732f77ee72f26cbf9ab693ba3601fe07ccf 100644 (file)
--- a/include/asm-i386/pda.h
+++ b/include/asm-i386/pda.h
@@ -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);

diff --git a/include/asm-i386/processor.h b/include/asm-i386/processor.h
index 01ae0ffcf236d55be22904392aed8eb567f76a7e..cd940befef53118bdf2dac42a6743528abe45c25 100644 (file)
--- a/include/asm-i386/processor.h
+++ b/include/asm-i386/processor.h
@@ -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);