[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/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