[PATCH] i386: Implement smp_processor_id() with the PDA

Use the cpu_number in the PDA to implement raw_smp_processor_id.  This is a
little simpler than using thread_info, though the cpu field in thread_info
cannot be removed since it is used for things other than getting the current
CPU in common code.
Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Cc: Chuck Ebbert <76306.1226@compuserve.com>
Cc: Zachary Amsden <zach@vmware.com>
Cc: Jan Beulich <jbeulich@novell.com>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>

arch/i386/kernel/asm-offsets.c

@@ -51,7 +51,6 @@ void foo(void)
 	OFFSET(TI_exec_domain, thread_info, exec_domain);
 	OFFSET(TI_flags, thread_info, flags);
 	OFFSET(TI_status, thread_info, status);
-	OFFSET(TI_cpu, thread_info, cpu);
 	OFFSET(TI_preempt_count, thread_info, preempt_count);
 	OFFSET(TI_addr_limit, thread_info, addr_limit);
 	OFFSET(TI_restart_block, thread_info, restart_block);
@@ -97,4 +96,7 @@ void foo(void)
 	DEFINE(VDSO_PRELINK, VDSO_PRELINK);
 
 	OFFSET(crypto_tfm_ctx_offset, crypto_tfm, __crt_ctx);
+
+	BLANK();
+ 	OFFSET(PDA_cpu, i386_pda, cpu_number);
 }

arch/i386/kernel/cpu/common.c

@@ -650,6 +650,7 @@ __cpuinit int alloc_gdt(int cpu)
 /* Initial PDA used by boot CPU */
 struct i386_pda boot_pda = {
 	._pda = &boot_pda,
+	.cpu_number = 0,
 };
 
 static inline void set_kernel_gs(void)
@@ -694,6 +695,7 @@ __cpuinit int init_gdt(int cpu, struct task_struct *idle)
 
 	memset(pda, 0, sizeof(*pda));
 	pda->_pda = pda;
+	pda->cpu_number = cpu;
 
 	return 1;
 }

arch/i386/kernel/entry.S

@@ -524,8 +524,7 @@ syscall_badsys:
 
 #define FIXUP_ESPFIX_STACK \
 	/* since we are on a wrong stack, we cant make it a C code :( */ \
-	GET_THREAD_INFO(%ebp); \
-	movl TI_cpu(%ebp), %ebx; \
+	movl %gs:PDA_cpu, %ebx; \
 	PER_CPU(cpu_gdt_descr, %ebx); \
 	movl GDS_address(%ebx), %ebx; \
 	GET_DESC_BASE(GDT_ENTRY_ESPFIX_SS, %ebx, %eax, %ax, %al, %ah); \

include/asm-i386/pda.h

@@ -11,6 +11,8 @@
 struct i386_pda
 {
 	struct i386_pda *_pda;		/* pointer to self */
+
+	int cpu_number;
 };
 
 extern struct i386_pda *_cpu_pda[];

include/asm-i386/smp.h

@@ -8,6 +8,7 @@
 #include <linux/kernel.h>
 #include <linux/threads.h>
 #include <linux/cpumask.h>
+#include <asm/pda.h>
 #endif
 
 #ifdef CONFIG_X86_LOCAL_APIC
@@ -56,7 +57,7 @@ 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() (current_thread_info()->cpu)
+#define raw_smp_processor_id() (read_pda(cpu_number))
 
 extern cpumask_t cpu_callout_map;
 extern cpumask_t cpu_callin_map;