[PATCH 3/8] Initialize the per-CPU data area.

Jeremy Fitzhardinge
2006-08-31T00:12:35Z

[-- Attachment #1: i386-pda-init.patch --]
[-- Type: text/plain, Size: 8176 bytes --]

When a CPU is brought up, a PDA and GDT are allocated for it. The
GDT's __KERNEL_PDA entry is pointed to the allocated PDA memory, so
that all references using this segment descriptor will refer to the PDA.

This patch rearranges CPU initialization a bit, so that the GDT/PDA
are set up as early as possible in cpu_init(). Also for secondary
CPUs, GDT+PDA are preallocated so the secondary CPU doesn't need to do
any memory allocation while setting up the PDA. This will be
important once smp_processor_id() and current use the PDA.

Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com>
Cc: Chuck Ebbert <76306.1226@compuserve.com>
Cc: Zachary Amsden <zach@vmware.com>
Cc: Jan Beulich <jbeulich@novell.com>
Cc: Andi Kleen <ak@suse.de>

---
arch/i386/kernel/cpu/common.c | 159 +++++++++++++++++++++++++++++------------
arch/i386/kernel/smpboot.c | 10 ++
include/asm-i386/processor.h | 1
3 files changed, 125 insertions(+), 45 deletions(-)

===================================================================
--- a/arch/i386/kernel/cpu/common.c
+++ b/arch/i386/kernel/cpu/common.c
@@ -18,6 +18,7 @@
#include <asm/apic.h>
#include <mach_apic.h>
#endif
+#include <asm/pda.h>

#include "cpu.h"

@@ -26,6 +27,9 @@ 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);
+
+struct i386_pda *_cpu_pda[NR_CPUS] __read_mostly;
+EXPORT_SYMBOL(_cpu_pda);

static int cachesize_override __cpuinitdata = -1;
static int disable_x86_fxsr __cpuinitdata;
@@ -582,6 +586,112 @@ void __init early_cpu_init(void)
disable_pse = 1;
#endif
}
+
+__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;
+}
+
+static __cpuinit void pda_init(int cpu, struct task_struct *curr)
+{
+ struct i386_pda *pda = cpu_pda(cpu);
+
+ memset(pda, 0, sizeof(*pda));
+
+ pda->cpu_number = cpu;
+ pda->pcurrent = curr;
+
+ printk("cpu %d current %p\n", cpu, curr);
+}
+
+/* Initialize the CPU's GDT and PDA */
+static __cpuinit void init_gdt(void)
+{
+ int cpu = smp_processor_id();
+ struct task_struct *curr = current;
+ struct Xgt_desc_struct *cpu_gdt_descr = &per_cpu(cpu_gdt_descr, cpu);
+ __u32 stk16_off = (__u32)&per_cpu(cpu_16bit_stack, 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);
+ for (;;)
+ local_irq_enable();
+ }
+
+ 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->size = GDT_SIZE - 1;
+
+ /* Set up GDT entry for 16bit stack */
+ *(__u64 *)(&gdt[GDT_ENTRY_ESPFIX_SS]) |=
+ ((((__u64)stk16_off) << 16) & 0x000000ffffff0000ULL) |
+ ((((__u64)stk16_off) << 32) & 0xff00000000000000ULL) |
+ (CPU_16BIT_STACK_SIZE - 1);
+
+ pack_descriptor((u32 *)&gdt[GDT_ENTRY_PDA].a,
+ (u32 *)&gdt[GDT_ENTRY_PDA].b,
+ (unsigned long)pda, sizeof(*pda) - 1,
+ 0x80 | DESCTYPE_S | 0x2, 0); /* present read-write data segment */
+
+ load_gdt(cpu_gdt_descr);
+
+ /* Do this once everything GDT-related has been set up. */
+ pda_init(cpu, curr);
+}
+
/*
* cpu_init() initializes state that is per-CPU. Some data is already
* initialized (naturally) in the bootstrap process, such as the GDT
@@ -593,14 +703,16 @@ void __cpuinit cpu_init(void)
int cpu = smp_processor_id();
struct tss_struct * t = &per_cpu(init_tss, cpu);
struct thread_struct *thread = &current->thread;
- struct desc_struct *gdt;
- __u32 stk16_off = (__u32)&per_cpu(cpu_16bit_stack, cpu);
- struct Xgt_desc_struct *cpu_gdt_descr = &per_cpu(cpu_gdt_descr, cpu);

if (cpu_test_and_set(cpu, cpu_initialized)) {
printk(KERN_WARNING "CPU#%d already initialized!\n", cpu);
for (;;) local_irq_enable();
}
+
+ /* Init the GDT and PDA early, before calling printk(),
+ since it may end up using the PDA indirectly. */
+ init_gdt();
+
printk(KERN_INFO "Initializing CPU#%d\n", cpu);

if (cpu_has_vme || cpu_has_tsc || cpu_has_de)
@@ -612,47 +724,6 @@ void __cpuinit cpu_init(void)
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 */
- *(__u64 *)(&gdt[GDT_ENTRY_ESPFIX_SS]) |=
- ((((__u64)stk16_off) << 16) & 0x000000ffffff0000ULL) |
- ((((__u64)stk16_off) << 32) & 0xff00000000000000ULL) |
- (CPU_16BIT_STACK_SIZE - 1);
-
- cpu_gdt_descr->size = GDT_SIZE - 1;
- cpu_gdt_descr->address = (unsigned long)gdt;
-
- load_gdt(cpu_gdt_descr);
load_idt(&idt_descr);

/*
===================================================================
--- a/arch/i386/kernel/smpboot.c
+++ b/arch/i386/kernel/smpboot.c
@@ -536,7 +536,7 @@ static void __devinit start_secondary(vo
static void __devinit start_secondary(void *unused)
{
/*
- * Dont put anything before smp_callin(), SMP
+ * Don't put *anything* before cpu_init(), SMP
* booting is too fragile that we want to limit the
* things done here to the most necessary things.
*/
@@ -931,6 +931,14 @@ static int __devinit do_boot_cpu(int api
int timeout;
unsigned long start_eip;
unsigned short nmi_high = 0, nmi_low = 0;
+
+ /* Pre-allocate the CPU's GDT and PDA so it doesn't have to do
+ any memory allocation during the delicate CPU-bringup
+ phase. */
+ if (!alloc_gdt(cpu)) {
+ printk(KERN_INFO "Couldn't allocate GDT/PDA for CPU %d\n", cpu);
+ return -1; /* ? */
+ }

++cpucount;
alternatives_smp_switch(1);
===================================================================
--- a/include/asm-i386/processor.h
+++ b/include/asm-i386/processor.h
@@ -726,5 +726,6 @@ extern unsigned long boot_option_idle_ov
extern unsigned long boot_option_idle_override;
extern void enable_sep_cpu(void);
extern int sysenter_setup(void);
+extern int alloc_gdt(int cpu);

#endif /* __ASM_I386_PROCESSOR_H */

--