amd64: Restore segmentation tables and registers also for boot CPU

After resume from system suspend, the kernel idle thread ended up with
an incorrect code segment selector, 0x18 (LONG_CS from tramp-realmode.h)
instead of 0x08 (GDT_CODE_KERNEL).

Change-Id: I177d120c73ac090acda7ea5f523e9fe6ec931041

src/kern/ia32/cpu-ia32.cpp

@@ -1610,20 +1610,19 @@ PUBLIC FIASCO_INIT_AND_PM
 void
 Cpu::pm_resume()
 {
+  set_gdt();
+  set_ldt(0);
+
+  set_ds(Gdt::data_segment());
+  set_es(Gdt::data_segment());
+  set_ss(Gdt::gdt_data_kernel | Gdt::Selector_kernel);
+  set_fs(Gdt::gdt_data_user   | Gdt::Selector_user);
+  set_gs(Gdt::gdt_data_user   | Gdt::Selector_user);
+  set_cs();
+
+  // the boot CPU restores TSS in asm already
   if (id() != Cpu_number::boot_cpu())
-    {
-      // the boot CPU restores some state in asm already
-      set_gdt();
-      set_ldt(0);
-      set_ds(Gdt::data_segment());
-      set_es(Gdt::data_segment());
-      set_ss(Gdt::gdt_data_kernel | Gdt::Selector_kernel);
-      set_fs(Gdt::gdt_data_user   | Gdt::Selector_user);
-      set_gs(Gdt::gdt_data_user   | Gdt::Selector_user);
-      set_cs();
-
-      set_tss();
-    }
+    set_tss();
 
   if (_vendor == Vendor_intel)
     Ia32_intel_microcode::load();

src/kern/ia32/tramp-acpi.S

@@ -75,13 +75,6 @@ _tramp_acpi_wakeup:
   lidt _idt
   lldt _ldt
 
-#if 0
-  movw _fs, %ax
-  movw %ax, %fs
-  movw _gs, %ax
-  movw %ax, %gs
-#endif
-
   /* restore general purpose registers */
 #ifdef CONFIG_AMD64
   mov _sp, %rsp
@@ -136,10 +129,6 @@ _idt:   .quad 0
         .quad 0
 _ldt:   .quad 0
         .quad 0
-#if 0
-_fs:    .word 0
-_gs:    .word 0
-#endif
 
 _tr:    .quad 0 /* task register */
         .quad 0
@@ -192,13 +181,6 @@ acpi_save_cpu_and_suspend:
   mov %cr4, %BX
   mov %BX, _cr4
 
-#if 0
-  movw %fs, %bx
-  movw %bx, _fs
-  movw %gs, %bx
-  movw %bx, _gs
-#endif
-
   str _tr
   /* save descriptor table (registers) */
   sgdt _gdt