On Tue, 2006-09-19 at 13:13 +1000, Rusty Russell wrote:
> Hi Jeremy, all,
>
> Sorry this took so long, spent last week in Japan at OSDL conf then
> netconf. After several false starts, I ended up with a very simple
> implementation, which clashes significantly with your work since then
> 8(. I've pushed the patches anyway, but it's going to be significant
> work for me to re-merge them, so I wanted your feedback first.
OK, here's a patch against 2.6.18-rc6-mm2. Tested on UP and SMP.
Crashes on hotplugging CPU, but crashes in same way as before the patch
8).
Replace PDA with per-cpu section, and put GDT in per-cpu section.
This patch uses the "gs" segment register which Jeremy Fitzhardinge
freed up for kernel use, for the per-cpu section. This means that
instead of having a special per-cpu struct which we can access in a
single instruction, any per-cpu variable can be accessed in a single
instruction. In addition, it avoids introducing the concept of a
"pda" into the kernel, in favour of the well-known "percpu" concept.
So, arch-specific code (eg. smp_processor_id()) can use
x86_write_percpu()/x86_read_percpu() directly. Generic code expects
an lvalue from __get_cpu_var(), but it takes two instruction to get
the address of a per-cpu variable (still not bad). Ideally, we could
use the __thread extension, and GCC would then generate optimal code
when an lvalue isn't needed, however, the linker wants to use a
negative offset within the gs register, which cannot be used with Xen
(or any similar hypervisor), because it requires a 4GB segment, which
would allow the OS to access the hypervisor memory.
As an additional simplification, the GDT is placed directly in a
per-cpu variable, rather than allocated dynamically. This is optimal
for the UP case (previously, we made a copy even here), and
signficantly simplfies the code. It's a little unusual to have asm
access a per-cpu var, but it is only done early at boot, where the
per-cpu GDT is sitting in the to-be-discarded section.
More cleanups/optimizations are possible:
1) Don't save/restore %gs on UP. The cost is measurable, and we don't use it.
2) Remove early_smp_processor_id(), by setting up the per-cpu
processor_id field correctly before starting a CPU.
3) Similarly, get rid of early_current().
4) Implement cpu_local_* in terms of x86_read_percpu etc.
Signed-off-by: Rusty Russell <[EMAIL PROTECTED]>
diff -urpN --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/dontdiff
--minimal linux-2.6.18-rc6-mm2/arch/i386/kernel/cpu/common.c
working-2.6.18-rc6-mm2-pda-to-percpu/arch/i386/kernel/cpu/common.c
--- linux-2.6.18-rc6-mm2/arch/i386/kernel/cpu/common.c 2006-09-19
14:54:22.000000000 +1000
+++ working-2.6.18-rc6-mm2-pda-to-percpu/arch/i386/kernel/cpu/common.c
2006-09-19 15:27:29.000000000 +1000
@@ -19,18 +19,14 @@
#include <asm/apic.h>
#include <mach_apic.h>
#endif
-#include <asm/pda.h>
#include "cpu.h"
-DEFINE_PER_CPU(struct Xgt_desc_struct, cpu_gdt_descr);
-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);
+DEFINE_PER_CPU(struct task_struct *, current_task) = &init_task;
+EXPORT_PER_CPU_SYMBOL(current_task);
static int cachesize_override __cpuinitdata = -1;
static int disable_x86_fxsr __cpuinitdata;
@@ -592,141 +587,10 @@ void __init early_cpu_init(void)
struct pt_regs * __devinit idle_regs(struct pt_regs *regs)
{
memset(regs, 0, sizeof(struct pt_regs));
- regs->xgs = __KERNEL_PDA;
+ regs->xgs = __KERNEL_PERCPU;
return regs;
}
-__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);
-}
-
-static inline void set_kernel_gs(void)
-{
- /* Set %gs for this CPU's PDA. Memory clobber is to create a
- barrier with respect to any PDA operations, so the compiler
- doesn't move any before here. */
- asm volatile ("mov %0, %%gs" : : "r" (__KERNEL_PDA) : "memory");
-}
-
-/* Initialize the CPU's GDT and PDA */
-static __cpuinit void init_gdt(void)
-{
- int cpu = early_smp_processor_id();
- struct task_struct *curr = early_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);
- set_kernel_gs();
-
- /* Do this once everything GDT-related has been set up. */
- pda_init(cpu, curr);
-}
-
-/* Set up a very early PDA for the boot CPU so that smp_processor_id()
- and current will work. */
-void __init smp_setup_processor_id(void)
-{
- static __initdata struct i386_pda boot_pda;
-
- pack_descriptor((u32 *)&cpu_gdt_table[GDT_ENTRY_PDA].a,
- (u32 *)&cpu_gdt_table[GDT_ENTRY_PDA].b,
- (unsigned long)&boot_pda, sizeof(struct i386_pda) - 1,
- 0x80 | DESCTYPE_S | 0x2, 0); /* present read-write data
segment */
-
- boot_pda.pcurrent = early_current();
-
- /* Set %gs for this CPU's PDA */
- set_kernel_gs();
-}
-
/*
* cpu_init() initializes state that is per-CPU. Some data is already
* initialized (naturally) in the bootstrap process, such as the GDT
@@ -740,15 +604,27 @@ void __cpuinit cpu_init(void)
struct tss_struct * t = &per_cpu(init_tss, cpu);
struct thread_struct *thread = &curr->thread;
+ struct desc_struct *gdt;
+ u32 stk16_off;
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();
+ /* Complete percpu area setup early, before calling printk(),
+ since it may end up using it indirectly. */
+ setup_percpu_for_this_cpu(cpu);
+ /* FIXME: Always the idle thread, can get rid of early_current. */
+ __get_cpu_var(current_task) = curr;
+
+ /* Set up GDT entry for 16bit stack */
+ stk16_off = (u32)&__get_cpu_var(cpu_16bit_stack);
+ gdt = __get_cpu_var(cpu_gdt_table);
+ *(__u64 *)(&gdt[GDT_ENTRY_ESPFIX_SS]) |=
+ ((((__u64)stk16_off) << 16) & 0x000000ffffff0000ULL) |
+ ((((__u64)stk16_off) << 32) & 0xff00000000000000ULL) |
+ (CPU_16BIT_STACK_SIZE - 1);
printk(KERN_INFO "Initializing CPU#%d\n", cpu);
diff -urpN --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/dontdiff
--minimal linux-2.6.18-rc6-mm2/arch/i386/kernel/entry.S
working-2.6.18-rc6-mm2-pda-to-percpu/arch/i386/kernel/entry.S
--- linux-2.6.18-rc6-mm2/arch/i386/kernel/entry.S 2006-09-19
14:54:23.000000000 +1000
+++ working-2.6.18-rc6-mm2-pda-to-percpu/arch/i386/kernel/entry.S
2006-09-19 15:26:28.000000000 +1000
@@ -125,7 +125,7 @@ VM_MASK = 0x00020000
movl $(__USER_DS), %edx; \
movl %edx, %ds; \
movl %edx, %es; \
- movl $(__KERNEL_PDA), %edx; \
+ movl $(__KERNEL_PERCPU), %edx; \
movl %edx, %gs
#define RESTORE_INT_REGS \
@@ -638,7 +638,7 @@ error_code:
movl $(__USER_DS), %ecx
movl %ecx, %ds
movl %ecx, %es
- movl $(__KERNEL_PDA), %ecx
+ movl $(__KERNEL_PERCPU), %ecx
movl %ecx, %gs
movl %esp,%eax # pt_regs pointer
call *%edi
diff -urpN --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/dontdiff
--minimal linux-2.6.18-rc6-mm2/arch/i386/kernel/head.S
working-2.6.18-rc6-mm2-pda-to-percpu/arch/i386/kernel/head.S
--- linux-2.6.18-rc6-mm2/arch/i386/kernel/head.S 2006-09-19
14:54:23.000000000 +1000
+++ working-2.6.18-rc6-mm2-pda-to-percpu/arch/i386/kernel/head.S
2006-09-19 15:23:48.000000000 +1000
@@ -302,7 +302,7 @@ is386: movl $2,%ecx # set MP
movl %eax,%cr0
call check_x87
- lgdt cpu_gdt_descr
+ lgdt per_cpu__cpu_gdt_descr
lidt idt_descr
ljmp $(__KERNEL_CS),$1f
1: movl $(__KERNEL_DS),%eax # reload all the segment registers
@@ -523,12 +523,6 @@ idt_descr:
.word IDT_ENTRIES*8-1 # idt contains 256 entries
.long idt_table
-# boot GDT descriptor (later on used by CPU#0):
- .word 0 # 32 bit align gdt_desc.address
-cpu_gdt_descr:
- .word GDT_ENTRIES*8-1
- .long cpu_gdt_table
-
/*
* The boot_gdt_table must mirror the equivalent in setup.S and is
* used only for booting.
@@ -539,55 +533,3 @@ ENTRY(boot_gdt_table)
.quad 0x00cf9a000000ffff /* kernel 4GB code at 0x00000000 */
.quad 0x00cf92000000ffff /* kernel 4GB data at 0x00000000 */
-/*
- * The Global Descriptor Table contains 28 quadwords, per-CPU.
- */
- .align L1_CACHE_BYTES
-ENTRY(cpu_gdt_table)
- .quad 0x0000000000000000 /* NULL descriptor */
- .quad 0x0000000000000000 /* 0x0b reserved */
- .quad 0x0000000000000000 /* 0x13 reserved */
- .quad 0x0000000000000000 /* 0x1b reserved */
- .quad 0x0000000000000000 /* 0x20 unused */
- .quad 0x0000000000000000 /* 0x28 unused */
- .quad 0x0000000000000000 /* 0x33 TLS entry 1 */
- .quad 0x0000000000000000 /* 0x3b TLS entry 2 */
- .quad 0x0000000000000000 /* 0x43 TLS entry 3 */
- .quad 0x0000000000000000 /* 0x4b reserved */
- .quad 0x0000000000000000 /* 0x53 reserved */
- .quad 0x0000000000000000 /* 0x5b reserved */
-
- .quad 0x00cf9a000000ffff /* 0x60 kernel 4GB code at 0x00000000 */
- .quad 0x00cf92000000ffff /* 0x68 kernel 4GB data at 0x00000000 */
- .quad 0x00cffa000000ffff /* 0x73 user 4GB code at 0x00000000 */
- .quad 0x00cff2000000ffff /* 0x7b user 4GB data at 0x00000000 */
-
- .quad 0x0000000000000000 /* 0x80 TSS descriptor */
- .quad 0x0000000000000000 /* 0x88 LDT descriptor */
-
- /*
- * Segments used for calling PnP BIOS have byte granularity.
- * They code segments and data segments have fixed 64k limits,
- * the transfer segment sizes are set at run time.
- */
- .quad 0x00409a000000ffff /* 0x90 32-bit code */
- .quad 0x00009a000000ffff /* 0x98 16-bit code */
- .quad 0x000092000000ffff /* 0xa0 16-bit data */
- .quad 0x0000920000000000 /* 0xa8 16-bit data */
- .quad 0x0000920000000000 /* 0xb0 16-bit data */
-
- /*
- * The APM segments have byte granularity and their bases
- * are set at run time. All have 64k limits.
- */
- .quad 0x00409a000000ffff /* 0xb8 APM CS code */
- .quad 0x00009a000000ffff /* 0xc0 APM CS 16 code (16 bit) */
- .quad 0x004092000000ffff /* 0xc8 APM DS data */
-
- .quad 0x0000920000000000 /* 0xd0 - ESPFIX 16-bit SS */
- .quad 0x0000000000000000 /* 0xd8 - PDA */
- .quad 0x0000000000000000 /* 0xe0 - unused */
- .quad 0x0000000000000000 /* 0xe8 - unused */
- .quad 0x0000000000000000 /* 0xf0 - unused */
- .quad 0x0000000000000000 /* 0xf8 - GDT entry 31: double-fault
TSS */
-
diff -urpN --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/dontdiff
--minimal linux-2.6.18-rc6-mm2/arch/i386/kernel/process.c
working-2.6.18-rc6-mm2-pda-to-percpu/arch/i386/kernel/process.c
--- linux-2.6.18-rc6-mm2/arch/i386/kernel/process.c 2006-09-19
14:54:24.000000000 +1000
+++ working-2.6.18-rc6-mm2-pda-to-percpu/arch/i386/kernel/process.c
2006-09-19 15:26:28.000000000 +1000
@@ -38,6 +38,7 @@
#include <linux/ptrace.h>
#include <linux/random.h>
#include <linux/personality.h>
+#include <linux/percpu.h>
#include <asm/uaccess.h>
#include <asm/pgtable.h>
@@ -56,7 +57,6 @@
#include <asm/tlbflush.h>
#include <asm/cpu.h>
-#include <asm/pda.h>
asmlinkage void ret_from_fork(void) __asm__("ret_from_fork");
@@ -345,7 +345,7 @@ int kernel_thread(int (*fn)(void *), voi
regs.xds = __USER_DS;
regs.xes = __USER_DS;
- regs.xgs = __KERNEL_PDA;
+ regs.xgs = __KERNEL_PERCPU;
regs.orig_eax = -1;
regs.eip = (unsigned long) kernel_thread_helper;
regs.xcs = __KERNEL_CS | get_kernel_rpl();
@@ -684,7 +684,7 @@ struct task_struct fastcall * __switch_t
if (unlikely(prev->fs | next->fs))
loadsegment(fs, next->fs);
- write_pda(pcurrent, next_p);
+ x86_write_percpu(current_task, next_p);
/*
* Restore IOPL if needed.
diff -urpN --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/dontdiff
--minimal linux-2.6.18-rc6-mm2/arch/i386/kernel/setup.c
working-2.6.18-rc6-mm2-pda-to-percpu/arch/i386/kernel/setup.c
--- linux-2.6.18-rc6-mm2/arch/i386/kernel/setup.c 2006-09-19
14:54:24.000000000 +1000
+++ working-2.6.18-rc6-mm2-pda-to-percpu/arch/i386/kernel/setup.c
2006-09-19 15:26:28.000000000 +1000
@@ -1470,6 +1470,52 @@ void __init setup_arch(char **cmdline_p)
tsc_init();
}
+/*
+ * The Global Descriptor Table contains 28 quadwords, per-CPU.
+ */
+__attribute__((aligned(L1_CACHE_BYTES)))
+DEFINE_PER_CPU(struct desc_struct, cpu_gdt_table[GDT_ENTRIES]) =
+{
+ /* kernel 4GB code at 0x00000000 */
+ [GDT_ENTRY_KERNEL_CS] = { 0x0000ffff, 0x00cf9a00 },
+ /* kernel 4GB data at 0x00000000 */
+ [GDT_ENTRY_KERNEL_DS] = { 0x0000ffff, 0x00cf9200 },
+ /* user 4GB code at 0x00000000 */
+ [GDT_ENTRY_DEFAULT_USER_CS] = { 0x0000ffff, 0x00cffa00 },
+ /* user 4GB data at 0x00000000 */
+ [GDT_ENTRY_DEFAULT_USER_DS] = { 0x0000ffff, 0x00cff200 },
+ /*
+ * Segments used for calling PnP BIOS have byte granularity.
+ * They code segments and data segments have fixed 64k limits,
+ * the transfer segment sizes are set at run time.
+ */
+ [GDT_ENTRY_PNPBIOS_BASE] =
+ { 0x0000ffff, 0x00409a00 }, /* 32-bit code */
+ { 0x0000ffff, 0x00009a00 }, /* 16-bit code */
+ { 0x0000ffff, 0x00009200 }, /* 16-bit data */
+ { 0x00000000, 0x00009200 }, /* 16-bit data */
+ { 0x00000000, 0x00009200 }, /* 16-bit data */
+
+ /*
+ * The APM segments have byte granularity and their bases
+ * are set at run time. All have 64k limits.
+ */
+ [GDT_ENTRY_APMBIOS_BASE] =
+ { 0x0000ffff, 0x00409a00 }, /* APM CS code */
+ { 0x0000ffff, 0x00009a00 }, /* APM CS 16 code (16 bit) */
+ { 0x0000ffff, 0x00409200 }, /* APM DS data */
+
+ /* ESPFIX 16-bit SS */
+ [GDT_ENTRY_ESPFIX_SS] = { 0x00000000, 0x00009200 },
+ /* FIXME: We save/restore %gs even on UP: fix entry.S. */
+ [GDT_ENTRY_PERCPU] = { 0x0000ffff, 0x00cf9200 },
+};
+
+/* Early in boot we use the master per-cpu gdt_table directly. */
+DEFINE_PER_CPU(struct Xgt_desc_struct, cpu_gdt_descr)
+= { .size = GDT_ENTRIES*8-1, .address = (long)&per_cpu__cpu_gdt_table };
+EXPORT_PER_CPU_SYMBOL(cpu_gdt_descr);
+
static __init int add_pcspkr(void)
{
struct platform_device *pd;
diff -urpN --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/dontdiff
--minimal linux-2.6.18-rc6-mm2/arch/i386/kernel/smpboot.c
working-2.6.18-rc6-mm2-pda-to-percpu/arch/i386/kernel/smpboot.c
--- linux-2.6.18-rc6-mm2/arch/i386/kernel/smpboot.c 2006-09-19
14:54:24.000000000 +1000
+++ working-2.6.18-rc6-mm2-pda-to-percpu/arch/i386/kernel/smpboot.c
2006-09-19 15:26:28.000000000 +1000
@@ -60,6 +60,9 @@
/* Set if we find a B stepping CPU */
static int __devinitdata smp_b_stepping;
+DEFINE_PER_CPU(unsigned int, processor_id);
+EXPORT_PER_CPU_SYMBOL(processor_id);
+
/* Number of siblings per CPU package */
int smp_num_siblings = 1;
#ifdef CONFIG_X86_HT
@@ -104,6 +107,9 @@ EXPORT_SYMBOL(x86_cpu_to_apicid);
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.
*/
@@ -934,14 +940,6 @@ static int __devinit do_boot_cpu(int api
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);
@@ -1072,7 +1070,6 @@ static int __cpuinit __smp_prepare_cpu(i
struct warm_boot_cpu_info info;
struct work_struct task;
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) {
@@ -1080,18 +1077,6 @@ 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;
@@ -1330,6 +1315,37 @@ static void __init smp_boot_cpus(unsigne
synchronize_tsc_bp();
}
+static inline void set_kernel_gs(void)
+{
+ /* Set %gs for this CPU's per-cpu area. Memory clobber is to create a
+ barrier with respect to any per-cpu operations, so the compiler
+ doesn't move any before here. */
+ asm volatile ("mov %0, %%gs" : : "r" (__KERNEL_PERCPU) : "memory");
+}
+
+static __cpuinit void setup_percpu_descriptor(struct desc_struct *gdt,
+ unsigned long per_cpu_off)
+{
+ unsigned limit, flags;
+
+ limit = (1 << 20);
+ flags = 0x8; /* 4k granularity */
+
+ /* present read-write data segment */
+ pack_descriptor((u32 *)&gdt->a, (u32 *)&gdt->b,
+ per_cpu_off, limit - 1,
+ 0x80 | DESCTYPE_S | 0x2, flags);
+}
+
+/* Set up a very early per-cpu for the boot CPU so that smp_processor_id()
+ and current will work. */
+void __init smp_setup_processor_id(void)
+{
+ /* We use the per-cpu template area (__per_cpu_offset[0] == 0). */
+ __per_cpu_offset[0] = 0;
+ setup_percpu_for_this_cpu(0);
+}
+
/* These are wrappers to interface to the new boot process. Someone
who understands all this stuff should rewrite it properly. --RR 15/Jul/02 */
void __init smp_prepare_cpus(unsigned int max_cpus)
@@ -1340,8 +1356,26 @@ void __init smp_prepare_cpus(unsigned in
smp_boot_cpus(max_cpus);
}
+/* Be careful not to use %gs references until this is setup: needs to
+ * be done on this CPU. */
+void __init setup_percpu_for_this_cpu(unsigned int cpu)
+{
+ struct desc_struct *gdt = per_cpu(cpu_gdt_table, cpu);
+ struct Xgt_desc_struct *cpu_gdt_descr = &per_cpu(cpu_gdt_descr, cpu);
+
+ per_cpu(processor_id, cpu) = cpu;
+ per_cpu(this_cpu_off, cpu) = __per_cpu_offset[cpu];
+ setup_percpu_descriptor(&gdt[GDT_ENTRY_PERCPU], __per_cpu_offset[cpu]);
+ cpu_gdt_descr->address = (unsigned long)gdt;
+ cpu_gdt_descr->size = GDT_SIZE - 1;
+ load_gdt(cpu_gdt_descr);
+ set_kernel_gs();
+}
+
void __devinit smp_prepare_boot_cpu(void)
{
+ setup_percpu_for_this_cpu(0);
+
cpu_set(smp_processor_id(), cpu_online_map);
cpu_set(smp_processor_id(), cpu_callout_map);
cpu_set(smp_processor_id(), cpu_present_map);
diff -urpN --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/dontdiff
--minimal linux-2.6.18-rc6-mm2/include/asm-i386/current.h
working-2.6.18-rc6-mm2-pda-to-percpu/include/asm-i386/current.h
--- linux-2.6.18-rc6-mm2/include/asm-i386/current.h 2006-09-19
14:55:55.000000000 +1000
+++ working-2.6.18-rc6-mm2-pda-to-percpu/include/asm-i386/current.h
2006-09-19 15:26:28.000000000 +1000
@@ -2,7 +2,7 @@
#define _I386_CURRENT_H
#include <linux/thread_info.h>
-#include <asm/pda.h>
+#include <asm/percpu.h>
struct task_struct;
@@ -11,11 +11,7 @@ static __always_inline struct task_struc
return current_thread_info()->task;
}
-static __always_inline struct task_struct *get_current(void)
-{
- return read_pda(pcurrent);
-}
-
-#define current get_current()
+DECLARE_PER_CPU(struct task_struct *, current_task);
+#define current x86_read_percpu(current_task)
#endif /* !(_I386_CURRENT_H) */
diff -urpN --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/dontdiff
--minimal linux-2.6.18-rc6-mm2/include/asm-i386/desc.h
working-2.6.18-rc6-mm2-pda-to-percpu/include/asm-i386/desc.h
--- linux-2.6.18-rc6-mm2/include/asm-i386/desc.h 2006-09-19
14:55:55.000000000 +1000
+++ working-2.6.18-rc6-mm2-pda-to-percpu/include/asm-i386/desc.h
2006-09-19 15:23:48.000000000 +1000
@@ -14,8 +14,8 @@
#include <asm/mmu.h>
-extern struct desc_struct cpu_gdt_table[GDT_ENTRIES];
-
+DECLARE_PER_CPU(struct desc_struct, cpu_gdt_table[GDT_ENTRIES]);
+DECLARE_PER_CPU(struct Xgt_desc_struct, cpu_gdt_descr);
DECLARE_PER_CPU(unsigned char, cpu_16bit_stack[CPU_16BIT_STACK_SIZE]);
struct Xgt_desc_struct {
@@ -25,8 +25,6 @@ struct Xgt_desc_struct {
} __attribute__ ((packed));
extern struct Xgt_desc_struct idt_descr;
-DECLARE_PER_CPU(struct Xgt_desc_struct, cpu_gdt_descr);
-
static inline struct desc_struct *get_cpu_gdt_table(unsigned int cpu)
{
diff -urpN --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/dontdiff
--minimal linux-2.6.18-rc6-mm2/include/asm-i386/pda.h
working-2.6.18-rc6-mm2-pda-to-percpu/include/asm-i386/pda.h
--- linux-2.6.18-rc6-mm2/include/asm-i386/pda.h 2006-09-19 14:55:56.000000000
+1000
+++ working-2.6.18-rc6-mm2-pda-to-percpu/include/asm-i386/pda.h 1970-01-01
10:00:00.000000000 +1000
@@ -1,68 +0,0 @@
-#ifndef _I386_PDA_H
-#define _I386_PDA_H
-
-struct i386_pda
-{
- struct task_struct *pcurrent; /* current process */
- int cpu_number;
-};
-
-extern struct i386_pda *_cpu_pda[];
-
-#define cpu_pda(i) (_cpu_pda[i])
-
-#define pda_offset(field) offsetof(struct i386_pda, field)
-
-extern void __bad_pda_field(void);
-
-extern struct i386_pda _proxy_pda;
-
-#define pda_to_op(op,field,val)
\
- do { \
- typedef typeof(_proxy_pda.field) T__; \
- if (0) { T__ tmp__; tmp__ = (val); } \
- switch (sizeof(_proxy_pda.field)) { \
- case 2: \
- asm(op "w %1,%%gs:%c2" \
- : "+m" (_proxy_pda.field) \
- :"ri" ((T__)val), \
- "i"(pda_offset(field))); \
- break; \
- case 4: \
- asm(op "l %1,%%gs:%c2" \
- : "+m" (_proxy_pda.field) \
- :"ri" ((T__)val), \
- "i"(pda_offset(field))); \
- break; \
- default: __bad_pda_field(); \
- } \
- } while (0)
-
-#define pda_from_op(op,field) \
- ({ \
- typeof(_proxy_pda.field) ret__; \
- switch (sizeof(_proxy_pda.field)) { \
- case 2: \
- asm(op "w %%gs:%c1,%0" \
- : "=r" (ret__) \
- : "i" (pda_offset(field)), \
- "m" (_proxy_pda.field)); \
- break; \
- case 4: \
- asm(op "l %%gs:%c1,%0" \
- : "=r" (ret__) \
- : "i" (pda_offset(field)), \
- "m" (_proxy_pda.field)); \
- break; \
- default: __bad_pda_field(); \
- } \
- ret__; })
-
-
-#define read_pda(field) pda_from_op("mov",field)
-#define write_pda(field,val) pda_to_op("mov",field,val)
-#define add_pda(field,val) pda_to_op("add",field,val)
-#define sub_pda(field,val) pda_to_op("sub",field,val)
-#define or_pda(field,val) pda_to_op("or",field,val)
-
-#endif /* _I386_PDA_H */
diff -urpN --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/dontdiff
--minimal linux-2.6.18-rc6-mm2/include/asm-i386/percpu.h
working-2.6.18-rc6-mm2-pda-to-percpu/include/asm-i386/percpu.h
--- linux-2.6.18-rc6-mm2/include/asm-i386/percpu.h 2004-02-04
14:44:44.000000000 +1100
+++ working-2.6.18-rc6-mm2-pda-to-percpu/include/asm-i386/percpu.h
2006-09-19 15:26:28.000000000 +1000
@@ -1,6 +1,107 @@
#ifndef __ARCH_I386_PERCPU__
#define __ARCH_I386_PERCPU__
+#ifdef CONFIG_SMP
+/* Same as generic implementation except for optimized local access. */
+#define __GENERIC_PER_CPU
+
+/* This is used for other cpus to find our section. */
+extern unsigned long __per_cpu_offset[NR_CPUS];
+
+/* Separate out the type, so (int[3], foo) works. */
+#define DECLARE_PER_CPU(type, name) extern __typeof__(type) per_cpu__##name
+#define DEFINE_PER_CPU(type, name) \
+ __attribute__((__section__(".data.percpu"))) __typeof__(type)
per_cpu__##name
+
+/* We can use this directly for local CPU (faster). */
+DECLARE_PER_CPU(unsigned long, this_cpu_off);
+
+/* var is in discarded region: offset to particular copy we want */
+#define per_cpu(var, cpu) (*({ \
+ extern int simple_indentifier_##var(void); \
+ RELOC_HIDE(&per_cpu__##var, __per_cpu_offset[cpu]); }))
+
+#define __raw_get_cpu_var(var) (*({ \
+ extern int simple_indentifier_##var(void); \
+ RELOC_HIDE(&per_cpu__##var, x86_read_percpu(this_cpu_off)); \
+}))
+
+#define __get_cpu_var(var) __raw_get_cpu_var(var)
+
+/* A macro to avoid #include hell... */
+#define percpu_modcopy(pcpudst, src, size) \
+do { \
+ unsigned int __i; \
+ for_each_possible_cpu(__i) \
+ memcpy((pcpudst)+__per_cpu_offset[__i], \
+ (src), (size)); \
+} while (0)
+
+#define EXPORT_PER_CPU_SYMBOL(var) EXPORT_SYMBOL(per_cpu__##var)
+#define EXPORT_PER_CPU_SYMBOL_GPL(var) EXPORT_SYMBOL_GPL(per_cpu__##var)
+
+/* gs segment starts at (positive) offset == __per_cpu_offset[cpu] */
+#define __percpu_seg "%%gs:"
+#else /* !SMP */
#include <asm-generic/percpu.h>
+#define __percpu_seg ""
+#endif /* SMP */
+
+/* For arch-specific code, we can use direct single-insn ops (they
+ * don't give an lvalue though). */
+extern void __bad_percpu_size(void);
+
+#define percpu_to_op(op,var,val) \
+ do { \
+ typedef typeof(var) T__; \
+ if (0) { T__ tmp__; tmp__ = (val); } \
+ switch (sizeof(var)) { \
+ case 1: \
+ asm(op "b %1,"__percpu_seg"%0" \
+ : "+m" (var) \
+ :"ri" ((T__)val)); \
+ break; \
+ case 2: \
+ asm(op "w %1,"__percpu_seg"%0" \
+ : "+m" (var) \
+ :"ri" ((T__)val)); \
+ break; \
+ case 4: \
+ asm(op "l %1,"__percpu_seg"%0" \
+ : "+m" (var) \
+ :"ri" ((T__)val)); \
+ break; \
+ default: __bad_percpu_size(); \
+ } \
+ } while (0)
+
+#define percpu_from_op(op,var) \
+ ({ \
+ typeof(var) ret__; \
+ switch (sizeof(var)) { \
+ case 1: \
+ asm(op "b "__percpu_seg"%1,%0" \
+ : "=r" (ret__) \
+ : "m" (var)); \
+ break; \
+ case 2: \
+ asm(op "w "__percpu_seg"%1,%0" \
+ : "=r" (ret__) \
+ : "m" (var)); \
+ break; \
+ case 4: \
+ asm(op "l "__percpu_seg"%1,%0" \
+ : "=r" (ret__) \
+ : "m" (var)); \
+ break; \
+ default: __bad_percpu_size(); \
+ } \
+ ret__; })
+
+#define x86_read_percpu(var) percpu_from_op("mov", per_cpu__##var)
+#define x86_write_percpu(var,val) percpu_to_op("mov", per_cpu__##var, val)
+#define x86_add_percpu(var,val) percpu_to_op("add", per_cpu__##var, val)
+#define x86_sub_percpu(var,val) percpu_to_op("sub", per_cpu__##var, val)
+#define x86_or_percpu(var,val) percpu_to_op("or", per_cpu__##var, val)
#endif /* __ARCH_I386_PERCPU__ */
diff -urpN --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/dontdiff
--minimal linux-2.6.18-rc6-mm2/include/asm-i386/processor.h
working-2.6.18-rc6-mm2-pda-to-percpu/include/asm-i386/processor.h
--- linux-2.6.18-rc6-mm2/include/asm-i386/processor.h 2006-09-19
14:55:56.000000000 +1000
+++ working-2.6.18-rc6-mm2-pda-to-percpu/include/asm-i386/processor.h
2006-09-19 15:26:28.000000000 +1000
@@ -473,7 +473,7 @@ struct thread_struct {
.vm86_info = NULL, \
.sysenter_cs = __KERNEL_CS, \
.io_bitmap_ptr = NULL, \
- .gs = __KERNEL_PDA, \
+ .gs = __KERNEL_PERCPU, \
}
/*
@@ -728,6 +728,5 @@ extern void select_idle_routine(const st
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 */
diff -urpN --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/dontdiff
--minimal linux-2.6.18-rc6-mm2/include/asm-i386/segment.h
working-2.6.18-rc6-mm2-pda-to-percpu/include/asm-i386/segment.h
--- linux-2.6.18-rc6-mm2/include/asm-i386/segment.h 2006-09-19
14:55:56.000000000 +1000
+++ working-2.6.18-rc6-mm2-pda-to-percpu/include/asm-i386/segment.h
2006-09-19 15:26:28.000000000 +1000
@@ -39,7 +39,7 @@
* 25 - APM BIOS support
*
* 26 - ESPFIX small SS
- * 27 - PDA [ per-cpu private data area ]
+ * 27 - PERCPU [ offset segment for per-cpu
area ]
* 28 - unused
* 29 - unused
* 30 - unused
@@ -74,8 +74,8 @@
#define GDT_ENTRY_ESPFIX_SS (GDT_ENTRY_KERNEL_BASE + 14)
#define __ESPFIX_SS (GDT_ENTRY_ESPFIX_SS * 8)
-#define GDT_ENTRY_PDA (GDT_ENTRY_KERNEL_BASE + 15)
-#define __KERNEL_PDA (GDT_ENTRY_PDA * 8)
+#define GDT_ENTRY_PERCPU (GDT_ENTRY_KERNEL_BASE + 15)
+#define __KERNEL_PERCPU (GDT_ENTRY_PERCPU * 8)
#define GDT_ENTRY_DOUBLEFAULT_TSS 31
diff -urpN --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/dontdiff
--minimal linux-2.6.18-rc6-mm2/include/asm-i386/smp.h
working-2.6.18-rc6-mm2-pda-to-percpu/include/asm-i386/smp.h
--- linux-2.6.18-rc6-mm2/include/asm-i386/smp.h 2006-09-19 14:55:56.000000000
+1000
+++ working-2.6.18-rc6-mm2-pda-to-percpu/include/asm-i386/smp.h 2006-09-19
15:27:59.000000000 +1000
@@ -8,7 +8,7 @@
#include <linux/kernel.h>
#include <linux/threads.h>
#include <linux/cpumask.h>
-#include <asm/pda.h>
+#include <asm/percpu.h>
#endif
#ifdef CONFIG_X86_LOCAL_APIC
@@ -59,7 +59,8 @@ extern void cpu_uninit(void);
* from the initial startup. We map APIC_BASE very early in page_setup(),
* so this is correct in the x86 case.
*/
-#define raw_smp_processor_id() (read_pda(cpu_number))
+DECLARE_PER_CPU(unsigned int, processor_id);
+#define raw_smp_processor_id() (x86_read_percpu(processor_id))
/* This is valid from the very earliest point in boot that we care
about. */
#define early_smp_processor_id() (current_thread_info()->cpu)
@@ -93,6 +94,8 @@ extern int __cpu_disable(void);
extern void __cpu_die(unsigned int cpu);
extern unsigned int num_processors;
+void setup_percpu_for_this_cpu(unsigned int cpu);
+
#endif /* !__ASSEMBLY__ */
#else /* CONFIG_SMP */
@@ -100,6 +103,7 @@ extern unsigned int num_processors;
#define safe_smp_processor_id() 0
#define cpu_physical_id(cpu) boot_cpu_physical_apicid
#define early_smp_processor_id() 0
+#define setup_percpu_for_this_cpu(cpu)
#define NO_PROC_ID 0xFF /* No processor magic marker */
diff -urpN --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/dontdiff
--minimal linux-2.6.18-rc6-mm2/include/asm-i386/unwind.h
working-2.6.18-rc6-mm2-pda-to-percpu/include/asm-i386/unwind.h
--- linux-2.6.18-rc6-mm2/include/asm-i386/unwind.h 2006-09-19
14:55:56.000000000 +1000
+++ working-2.6.18-rc6-mm2-pda-to-percpu/include/asm-i386/unwind.h
2006-09-19 15:26:28.000000000 +1000
@@ -65,7 +65,7 @@ static inline void arch_unw_init_blocked
info->regs.xss = __KERNEL_DS;
info->regs.xds = __USER_DS;
info->regs.xes = __USER_DS;
- info->regs.xgs = __KERNEL_PDA;
+ info->regs.xgs = __KERNEL_PERCPU;
}
extern asmlinkage int arch_unwind_init_running(struct unwind_frame_info *,
--
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