x86: merge 64 and 32 SMP percpu handling

Now that pda is allocated as part of percpu, percpu doesn't need to be
accessed through pda.  Unify x86_64 SMP percpu access with x86_32 SMP
one.  Other than the segment register, operand size and the base of
percpu symbols, they behave identical now.

This patch replaces now unnecessary pda->data_offset with a dummy
field which is necessary to keep stack_canary at its place.  This
patch also moves per_cpu_offset initialization out of init_gdt() into
setup_per_cpu_areas().  Note that this change also necessitates
explicit per_cpu_offset initializations in voyager_smp.c.

With this change, x86_OP_percpu()'s are as efficient on x86_64 as on
x86_32 and also x86_64 can use assembly PER_CPU macros.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 4 insertions, 3 deletions

diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index e28c7a987793..4833f3a19650 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -52,6 +52,7 @@
 #include <asm/irqflags.h>
 #include <asm/paravirt.h>
 #include <asm/ftrace.h>
+#include <asm/percpu.h>
 
 /* Avoid __ASSEMBLER__'ifying <linux/audit.h> just for this.  */
 #include <linux/elf-em.h>
@@ -1072,10 +1073,10 @@ ENTRY(\sym)
         TRACE_IRQS_OFF
         movq %rsp,%rdi          /* pt_regs pointer */
         xorl %esi,%esi          /* no error code */
-        movq %gs:pda_data_offset, %rbp
-        subq $EXCEPTION_STKSZ, per_cpu__init_tss + TSS_ist + (\ist - 1) * 8(%rbp)
+        PER_CPU(init_tss, %rbp)
+        subq $EXCEPTION_STKSZ, TSS_ist + (\ist - 1) * 8(%rbp)
         call \do_sym
-        addq $EXCEPTION_STKSZ, per_cpu__init_tss + TSS_ist + (\ist - 1) * 8(%rbp)
+        addq $EXCEPTION_STKSZ, TSS_ist + (\ist - 1) * 8(%rbp)
         jmp paranoid_exit       /* %ebx: no swapgs flag */
         CFI_ENDPROC
 END(\sym)