[PATCH] i386: Convert PDA into the percpu section
Currently x86 (similar to x84-64) has a special per-cpu structure
called "i386_pda" which can be easily and efficiently referenced via
the %fs register. An ELF section is more flexible than a structure,
allowing any piece of code to use this area. Indeed, such a section
already exists: the per-cpu area.
So this patch:
(1) Removes the PDA and uses per-cpu variables for each current member.
(2) Replaces the __KERNEL_PDA segment with __KERNEL_PERCPU.
(3) Creates a per-cpu mirror of __per_cpu_offset called this_cpu_off, which
can be used to calculate addresses for this CPU's variables.
(4) Simplifies startup, because %fs doesn't need to be loaded with a
special segment at early boot; it can be deferred until the first
percpu area is allocated (or never for UP).
The result is less code and one less x86-specific concept.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Cc: Andi Kleen <ak@suse.de>
diff --git a/arch/i386/kernel/asm-offsets.c b/arch/i386/kernel/asm-offsets.c
index d558adf..b05e85f 100644
--- a/arch/i386/kernel/asm-offsets.c
+++ b/arch/i386/kernel/asm-offsets.c
@@ -15,7 +15,6 @@
#include <asm/processor.h>
#include <asm/thread_info.h>
#include <asm/elf.h>
-#include <asm/pda.h>
#define DEFINE(sym, val) \
asm volatile("\n->" #sym " %0 " #val : : "i" (val))
@@ -101,10 +100,6 @@
OFFSET(crypto_tfm_ctx_offset, crypto_tfm, __crt_ctx);
- BLANK();
- OFFSET(PDA_cpu, i386_pda, cpu_number);
- OFFSET(PDA_pcurrent, i386_pda, pcurrent);
-
#ifdef CONFIG_PARAVIRT
BLANK();
OFFSET(PARAVIRT_enabled, paravirt_ops, paravirt_enabled);
diff --git a/arch/i386/kernel/cpu/common.c b/arch/i386/kernel/cpu/common.c
index 7a4c036..27e0056 100644
--- a/arch/i386/kernel/cpu/common.c
+++ b/arch/i386/kernel/cpu/common.c
@@ -18,7 +18,6 @@
#include <asm/apic.h>
#include <mach_apic.h>
#endif
-#include <asm/pda.h>
#include "cpu.h"
@@ -47,13 +46,10 @@
[GDT_ENTRY_APMBIOS_BASE+2] = { 0x0000ffff, 0x00409200 }, /* data */
[GDT_ENTRY_ESPFIX_SS] = { 0x00000000, 0x00c09200 },
- [GDT_ENTRY_PDA] = { 0x00000000, 0x00c09200 }, /* set in setup_pda */
+ [GDT_ENTRY_PERCPU] = { 0x00000000, 0x00000000 },
} };
EXPORT_PER_CPU_SYMBOL_GPL(gdt_page);
-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;
static int disable_x86_serial_nr __cpuinitdata = 1;
@@ -634,21 +630,14 @@
#endif
}
-/* Make sure %gs is initialized properly in idle threads */
+/* Make sure %fs is initialized properly in idle threads */
struct pt_regs * __devinit idle_regs(struct pt_regs *regs)
{
memset(regs, 0, sizeof(struct pt_regs));
- regs->xfs = __KERNEL_PDA;
+ regs->xfs = __KERNEL_PERCPU;
return regs;
}
-/* Initial PDA used by boot CPU */
-struct i386_pda boot_pda = {
- ._pda = &boot_pda,
- .cpu_number = 0,
- .pcurrent = &init_task,
-};
-
/*
* cpu_init() initializes state that is per-CPU. Some data is already
* initialized (naturally) in the bootstrap process, such as the GDT
diff --git a/arch/i386/kernel/entry.S b/arch/i386/kernel/entry.S
index 3e4aa1f..7f92ceb 100644
--- a/arch/i386/kernel/entry.S
+++ b/arch/i386/kernel/entry.S
@@ -132,7 +132,7 @@
movl $(__USER_DS), %edx; \
movl %edx, %ds; \
movl %edx, %es; \
- movl $(__KERNEL_PDA), %edx; \
+ movl $(__KERNEL_PERCPU), %edx; \
movl %edx, %fs
#define RESTORE_INT_REGS \
@@ -556,7 +556,6 @@
#define FIXUP_ESPFIX_STACK \
/* since we are on a wrong stack, we cant make it a C code :( */ \
- movl %fs:PDA_cpu, %ebx; \
PER_CPU(gdt_page, %ebx); \
GET_DESC_BASE(GDT_ENTRY_ESPFIX_SS, %ebx, %eax, %ax, %al, %ah); \
addl %esp, %eax; \
@@ -681,7 +680,7 @@
pushl %fs
CFI_ADJUST_CFA_OFFSET 4
/*CFI_REL_OFFSET fs, 0*/
- movl $(__KERNEL_PDA), %ecx
+ movl $(__KERNEL_PERCPU), %ecx
movl %ecx, %fs
UNWIND_ESPFIX_STACK
popl %ecx
diff --git a/arch/i386/kernel/head.S b/arch/i386/kernel/head.S
index bb36c24..12277d8 100644
--- a/arch/i386/kernel/head.S
+++ b/arch/i386/kernel/head.S
@@ -317,12 +317,12 @@
movl %eax,%cr0
call check_x87
- call setup_pda
lgdt early_gdt_descr
lidt idt_descr
ljmp $(__KERNEL_CS),$1f
1: movl $(__KERNEL_DS),%eax # reload all the segment registers
movl %eax,%ss # after changing gdt.
+ movl %eax,%fs # gets reset once there's real percpu
movl $(__USER_DS),%eax # DS/ES contains default USER segment
movl %eax,%ds
@@ -332,16 +332,17 @@
movl %eax,%gs
lldt %ax
- movl $(__KERNEL_PDA),%eax
- mov %eax,%fs
-
cld # gcc2 wants the direction flag cleared at all times
pushl $0 # fake return address for unwinder
#ifdef CONFIG_SMP
movb ready, %cl
movb $1, ready
cmpb $0,%cl # the first CPU calls start_kernel
- jne initialize_secondary # all other CPUs call initialize_secondary
+ je 1f
+ movl $(__KERNEL_PERCPU), %eax
+ movl %eax,%fs # set this cpu's percpu
+ jmp initialize_secondary # all other CPUs call initialize_secondary
+1:
#endif /* CONFIG_SMP */
jmp start_kernel
@@ -365,23 +366,6 @@
ret
/*
- * Point the GDT at this CPU's PDA. On boot this will be
- * cpu_gdt_table and boot_pda; for secondary CPUs, these will be
- * that CPU's GDT and PDA.
- */
-ENTRY(setup_pda)
- /* get the PDA pointer */
- movl start_pda, %eax
-
- /* slot the PDA address into the GDT */
- mov early_gdt_descr+2, %ecx
- mov %ax, (__KERNEL_PDA+0+2)(%ecx) /* base & 0x0000ffff */
- shr $16, %eax
- mov %al, (__KERNEL_PDA+4+0)(%ecx) /* base & 0x00ff0000 */
- mov %ah, (__KERNEL_PDA+4+3)(%ecx) /* base & 0xff000000 */
- ret
-
-/*
* setup_idt
*
* sets up a idt with 256 entries pointing to
@@ -553,9 +537,6 @@
* This starts the data section.
*/
.data
-ENTRY(start_pda)
- .long boot_pda
-
ENTRY(stack_start)
.long init_thread_union+THREAD_SIZE
.long __BOOT_DS
diff --git a/arch/i386/kernel/i386_ksyms.c b/arch/i386/kernel/i386_ksyms.c
index 4afe26e..e3d4b73 100644
--- a/arch/i386/kernel/i386_ksyms.c
+++ b/arch/i386/kernel/i386_ksyms.c
@@ -28,5 +28,3 @@
#endif
EXPORT_SYMBOL(csum_partial);
-
-EXPORT_SYMBOL(_proxy_pda);
diff --git a/arch/i386/kernel/irq.c b/arch/i386/kernel/irq.c
index 8db8d51..d2daf67 100644
--- a/arch/i386/kernel/irq.c
+++ b/arch/i386/kernel/irq.c
@@ -24,6 +24,9 @@
DEFINE_PER_CPU(irq_cpustat_t, irq_stat) ____cacheline_internodealigned_in_smp;
EXPORT_PER_CPU_SYMBOL(irq_stat);
+DEFINE_PER_CPU(struct pt_regs *, irq_regs);
+EXPORT_PER_CPU_SYMBOL(irq_regs);
+
/*
* 'what should we do if we get a hw irq event on an illegal vector'.
* each architecture has to answer this themselves.
diff --git a/arch/i386/kernel/process.c b/arch/i386/kernel/process.c
index 5fb9524..6199947 100644
--- a/arch/i386/kernel/process.c
+++ b/arch/i386/kernel/process.c
@@ -39,6 +39,7 @@
#include <linux/random.h>
#include <linux/personality.h>
#include <linux/tick.h>
+#include <linux/percpu.h>
#include <asm/uaccess.h>
#include <asm/pgtable.h>
@@ -57,7 +58,6 @@
#include <asm/tlbflush.h>
#include <asm/cpu.h>
-#include <asm/pda.h>
asmlinkage void ret_from_fork(void) __asm__("ret_from_fork");
@@ -66,6 +66,12 @@
unsigned long boot_option_idle_override = 0;
EXPORT_SYMBOL(boot_option_idle_override);
+DEFINE_PER_CPU(struct task_struct *, current_task) = &init_task;
+EXPORT_PER_CPU_SYMBOL(current_task);
+
+DEFINE_PER_CPU(int, cpu_number);
+EXPORT_PER_CPU_SYMBOL(cpu_number);
+
/*
* Return saved PC of a blocked thread.
*/
@@ -342,7 +348,7 @@
regs.xds = __USER_DS;
regs.xes = __USER_DS;
- regs.xfs = __KERNEL_PDA;
+ regs.xfs = __KERNEL_PERCPU;
regs.orig_eax = -1;
regs.eip = (unsigned long) kernel_thread_helper;
regs.xcs = __KERNEL_CS | get_kernel_rpl();
@@ -711,7 +717,7 @@
if (prev->gs | next->gs)
loadsegment(gs, next->gs);
- write_pda(pcurrent, next_p);
+ x86_write_percpu(current_task, next_p);
return prev_p;
}
diff --git a/arch/i386/kernel/smpboot.c b/arch/i386/kernel/smpboot.c
index 61e2842..f79b623 100644
--- a/arch/i386/kernel/smpboot.c
+++ b/arch/i386/kernel/smpboot.c
@@ -53,7 +53,6 @@
#include <asm/desc.h>
#include <asm/arch_hooks.h>
#include <asm/nmi.h>
-#include <asm/pda.h>
#include <mach_apic.h>
#include <mach_wakecpu.h>
@@ -99,6 +98,9 @@
u8 apicid_2_node[MAX_APICID];
+DEFINE_PER_CPU(unsigned long, this_cpu_off);
+EXPORT_PER_CPU_SYMBOL(this_cpu_off);
+
/*
* Trampoline 80x86 program as an array.
*/
@@ -456,7 +458,6 @@
void * esp;
unsigned short ss;
} stack_start;
-extern struct i386_pda *start_pda;
#ifdef CONFIG_NUMA
@@ -784,20 +785,17 @@
/* Initialize the CPU's GDT. This is either the boot CPU doing itself
(still using the master per-cpu area), or a CPU doing it for a
secondary which will soon come up. */
-static __cpuinit void init_gdt(int cpu, struct task_struct *idle)
+static __cpuinit void init_gdt(int cpu)
{
struct desc_struct *gdt = get_cpu_gdt_table(cpu);
- struct i386_pda *pda = &per_cpu(_cpu_pda, cpu);
- 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 */
+ pack_descriptor((u32 *)&gdt[GDT_ENTRY_PERCPU].a,
+ (u32 *)&gdt[GDT_ENTRY_PERCPU].b,
+ __per_cpu_offset[cpu], 0xFFFFF,
+ 0x80 | DESCTYPE_S | 0x2, 0x8);
- memset(pda, 0, sizeof(*pda));
- pda->_pda = pda;
- pda->cpu_number = cpu;
- pda->pcurrent = idle;
+ per_cpu(this_cpu_off, cpu) = __per_cpu_offset[cpu];
+ per_cpu(cpu_number, cpu) = cpu;
}
/* Defined in head.S */
@@ -824,9 +822,9 @@
if (IS_ERR(idle))
panic("failed fork for CPU %d", cpu);
- init_gdt(cpu, idle);
+ init_gdt(cpu);
+ per_cpu(current_task, cpu) = idle;
early_gdt_descr.address = (unsigned long)get_cpu_gdt_table(cpu);
- start_pda = cpu_pda(cpu);
idle->thread.eip = (unsigned long) start_secondary;
/* start_eip had better be page-aligned! */
@@ -1188,14 +1186,14 @@
gdt_descr.address = (long)get_cpu_gdt_table(smp_processor_id());
gdt_descr.size = GDT_SIZE - 1;
load_gdt(&gdt_descr);
- asm volatile ("mov %0, %%fs" : : "r" (__KERNEL_PDA) : "memory");
+ asm("mov %0, %%fs" : : "r" (__KERNEL_PERCPU) : "memory");
}
void __init native_smp_prepare_boot_cpu(void)
{
unsigned int cpu = smp_processor_id();
- init_gdt(cpu, current);
+ init_gdt(cpu);
switch_to_new_gdt();
cpu_set(cpu, cpu_online_map);
diff --git a/arch/i386/kernel/vmi.c b/arch/i386/kernel/vmi.c
index ccad7ee..1231298 100644
--- a/arch/i386/kernel/vmi.c
+++ b/arch/i386/kernel/vmi.c
@@ -504,8 +504,6 @@
#endif
#ifdef CONFIG_SMP
-extern void setup_pda(void);
-
static void __devinit
vmi_startup_ipi_hook(int phys_apicid, unsigned long start_eip,
unsigned long start_esp)
@@ -530,13 +528,11 @@
ap.ds = __USER_DS;
ap.es = __USER_DS;
- ap.fs = __KERNEL_PDA;
+ ap.fs = __KERNEL_PERCPU;
ap.gs = 0;
ap.eflags = 0;
- setup_pda();
-
#ifdef CONFIG_X86_PAE
/* efer should match BSP efer. */
if (cpu_has_nx) {
diff --git a/arch/i386/kernel/vmlinux.lds.S b/arch/i386/kernel/vmlinux.lds.S
index 2ce4aa1..d125784 100644
--- a/arch/i386/kernel/vmlinux.lds.S
+++ b/arch/i386/kernel/vmlinux.lds.S
@@ -26,7 +26,6 @@
OUTPUT_ARCH(i386)
ENTRY(phys_startup_32)
jiffies = jiffies_64;
-_proxy_pda = 1;
PHDRS {
text PT_LOAD FLAGS(5); /* R_E */