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Message-Id: <1173185734.4644.32.camel@localhost.localdomain>
Date: Tue, 06 Mar 2007 23:55:34 +1100
From: Rusty Russell <rusty@...tcorp.com.au>
To: lkml - Kernel Mailing List <linux-kernel@...r.kernel.org>
Cc: Zachary Amsden <zach@...are.com>,
Jeremy Fitzhardinge <jeremy@...source.com>,
Ingo Molnar <mingo@...e.hu>,
Andrew Morton <akpm@...ux-foundation.org>,
Andi Kleen <ak@...e.de>
Subject: [PATCH 3/8] 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, see later).
Finally, we can simply call it "cpu_gdt" rather than enduring the
superfluous and unnecessarily redundant tautology of "cpu_gdt_table".
Signed-off-by: Rusty Russell <rusty@...tcorp.com.au>
diff -r c2b61e13394d arch/i386/kernel/cpu/common.c
--- a/arch/i386/kernel/cpu/common.c Fri Mar 02 09:35:32 2007 +1100
+++ b/arch/i386/kernel/cpu/common.c Mon Mar 05 11:34:31 2007 +1100
@@ -25,8 +25,10 @@ DEFINE_PER_CPU(struct Xgt_desc_struct, c
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 boot_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);
-
- /*
- * Initialize the per-CPU GDT with the boot GDT,
- * and set up the GDT descriptor:
- */
+ struct desc_struct *gdt = per_cpu(cpu_gdt, cpu);
+ struct i386_pda *pda = &per_cpu(_cpu_pda, cpu);
+
memcpy(gdt, boot_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 +648,13 @@ __cpuinit int init_gdt(int cpu, struct t
pda->_pda = pda;
pda->cpu_number = cpu;
pda->pcurrent = idle;
-
- return 1;
-}
-
+}
+
+/* Move this CPU from boot_gdt_table & boot_pda to this cpu's proper one. */
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 +742,8 @@ 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 -r c2b61e13394d arch/i386/kernel/smpboot.c
--- a/arch/i386/kernel/smpboot.c Fri Mar 02 09:35:32 2007 +1100
+++ b/arch/i386/kernel/smpboot.c Fri Mar 02 10:59:18 2007 +1100
@@ -813,13 +813,7 @@ 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! */
@@ -945,24 +939,11 @@ 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) {
ret = -ENODEV;
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;
diff -r c2b61e13394d arch/i386/mach-voyager/voyager_smp.c
--- a/arch/i386/mach-voyager/voyager_smp.c Fri Mar 02 09:35:32 2007 +1100
+++ b/arch/i386/mach-voyager/voyager_smp.c Fri Mar 02 10:28:14 2007 +1100
@@ -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 -r c2b61e13394d include/asm-i386/desc.h
--- a/include/asm-i386/desc.h Fri Mar 02 09:35:32 2007 +1100
+++ b/include/asm-i386/desc.h Mon Mar 05 11:34:31 2007 +1100
@@ -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 -r c2b61e13394d include/asm-i386/pda.h
--- a/include/asm-i386/pda.h Fri Mar 02 09:35:32 2007 +1100
+++ b/include/asm-i386/pda.h Mon Mar 05 11:34:31 2007 +1100
@@ -8,6 +8,7 @@
#include <linux/stddef.h>
#include <linux/types.h>
+#include <asm/percpu.h>
struct i386_pda
{
@@ -18,9 +19,9 @@ struct i386_pda
struct pt_regs *irq_regs;
};
-extern struct i386_pda *_cpu_pda[];
+DECLARE_PER_CPU(struct i386_pda, _cpu_pda);
-#define cpu_pda(i) (_cpu_pda[i])
+#define cpu_pda(i) (&per_cpu(_cpu_pda, (i)))
#define pda_offset(field) offsetof(struct i386_pda, field)
diff -r c2b61e13394d include/asm-i386/processor.h
--- a/include/asm-i386/processor.h Fri Mar 02 09:35:32 2007 +1100
+++ b/include/asm-i386/processor.h Fri Mar 02 10:28:14 2007 +1100
@@ -750,7 +750,7 @@ extern void enable_sep_cpu(void);
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);
-
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