diff options
| author | Jeremy Fitzhardinge <jeremy@goop.org> | 2007-05-02 19:27:16 +0200 |
|---|---|---|
| committer | Andi Kleen <andi@basil.nowhere.org> | 2007-05-02 19:27:16 +0200 |
| commit | 7c3576d261ce046789a7db14f43303f8120910c7 (patch) | |
| tree | ad27a8459bbcdb183fe2411aec3b840942992ad5 /arch/i386/kernel/head.S | |
| parent | 7a61d35d4b4056e7711031202da7605e052f4137 (diff) | |
[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>
Diffstat (limited to 'arch/i386/kernel/head.S')
| -rw-r--r-- | arch/i386/kernel/head.S | 31 |
1 files changed, 6 insertions, 25 deletions
diff --git a/arch/i386/kernel/head.S b/arch/i386/kernel/head.S index bb36c24311b..12277d8938d 100644 --- a/arch/i386/kernel/head.S +++ b/arch/i386/kernel/head.S @@ -317,12 +317,12 @@ is386: movl $2,%ecx # set MP 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 @@ is386: movl $2,%ecx # set MP 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 @@ check_x87: 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 @@ ENTRY(empty_zero_page) * This starts the data section. */ .data -ENTRY(start_pda) - .long boot_pda - ENTRY(stack_start) .long init_thread_union+THREAD_SIZE .long __BOOT_DS |