[PATCH] Avoid overwriting boot_cpu_data from trampoline code

boot_cpu_data should contain the common capabilities of all cpus in the
system. identify_cpu [arch/i386/kernel/cpu/common.c] tries to enforce
that. But right now, the SMP trampoline code [arch/i386/kernel/head.S]
overwrites boot_cpu_data when the secondary cpus are started, i.e.
boot_cpu_data contains the capabilities from the last cpu that booted :-(

The attached patch adds a new, __initdata variable for the asm code.

arch/i386/kernel/head.S

@@ -23,10 +23,10 @@
 #define NEW_CL_POINTER		0x228	/* Relative to real mode data */
 
 /*
- * References to members of the boot_cpu_data structure.
+ * References to members of the new_cpu_data structure.
  */
 
-#define CPU_PARAMS	boot_cpu_data
+#define CPU_PARAMS	new_cpu_data
 #define X86		CPU_PARAMS+0
 #define X86_VENDOR	CPU_PARAMS+1
 #define X86_MODEL	CPU_PARAMS+2

arch/i386/kernel/setup.c

@@ -50,6 +50,9 @@ static inline char * __init machine_specific_memory_setup(void);
  */
 
 char ignore_irq13;		/* set if exception 16 works */
+/* cpu data as detected by the assembly code in head.S */
+struct cpuinfo_x86 new_cpu_data __initdata = { 0, 0, 0, 0, -1, 1, 0, 0, -1 };
+/* common cpu data for all cpus */
 struct cpuinfo_x86 boot_cpu_data = { 0, 0, 0, 0, -1, 1, 0, 0, -1 };
 
 unsigned long mmu_cr4_features;
@@ -840,6 +843,7 @@ void __init setup_arch(char **cmdline_p)
 {
 	unsigned long max_low_pfn;
 
+	memcpy(&boot_cpu_data, &new_cpu_data, sizeof(new_cpu_data));
 	pre_setup_arch_hook();
 	early_cpu_init();
 

include/asm-i386/processor.h

@@ -78,6 +78,7 @@ struct cpuinfo_x86 {
  */
 
 extern struct cpuinfo_x86 boot_cpu_data;
+extern struct cpuinfo_x86 new_cpu_data;
 extern struct tss_struct init_tss[NR_CPUS];
 
 #ifdef CONFIG_SMP