3 files changed, 20 insertions, 3 deletions
diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index cd022c43dfbc..aed7ceeb4b65 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -66,6 +66,8 @@ EXPORT_SYMBOL_GPL(xen_start_info);
 
 struct shared_info xen_dummy_shared_info;
 
+void *xen_initial_gdt;
+
 /*
  * Point at some empty memory to start with. We map the real shared_info
  * page as soon as fixmap is up and running.
@@ -917,8 +919,19 @@ asmlinkage void __init xen_start_kernel(void)
 	have_vcpu_info_placement = 0;
 #endif
 
-	/* setup percpu state */
+#ifdef CONFIG_X86_64
+	/*
+	 * Setup percpu state.  We only need to do this for 64-bit
+	 * because 32-bit already has %fs set properly.
+	 */
 	load_percpu_segment(0);
+#endif
+	/*
+	 * The only reliable way to retain the initial address of the
+	 * percpu gdt_page is to remember it here, so we can go and
+	 * mark it RW later, when the initial percpu area is freed.
+	 */
+	xen_initial_gdt = &per_cpu(gdt_page, 0);
 
 	xen_smp_init();
 
diff --git a/arch/x86/xen/smp.c b/arch/x86/xen/smp.c
index 88d5d5ec6beb..035582ae815d 100644
--- a/arch/x86/xen/smp.c
+++ b/arch/x86/xen/smp.c
@@ -170,8 +170,7 @@ static void __init xen_smp_prepare_boot_cpu(void)
 
 	/* We've switched to the "real" per-cpu gdt, so make sure the
 	   old memory can be recycled */
-	make_lowmem_page_readwrite(__per_cpu_load +
-				   (unsigned long)&per_cpu_var(gdt_page));
+	make_lowmem_page_readwrite(xen_initial_gdt);
 
 	xen_setup_vcpu_info_placement();
 }
@@ -287,6 +286,9 @@ static int __cpuinit xen_cpu_up(unsigned int cpu)
 	irq_ctx_init(cpu);
 #else
 	clear_tsk_thread_flag(idle, TIF_FORK);
+	per_cpu(kernel_stack, cpu) =
+		(unsigned long)task_stack_page(idle) -
+		KERNEL_STACK_OFFSET + THREAD_SIZE;
 #endif
 	xen_setup_timer(cpu);
 	xen_init_lock_cpu(cpu);
diff --git a/arch/x86/xen/xen-ops.h b/arch/x86/xen/xen-ops.h
index 11913fc94c14..2f5ef2632ea2 100644
--- a/arch/x86/xen/xen-ops.h
+++ b/arch/x86/xen/xen-ops.h
@@ -10,6 +10,8 @@
 extern const char xen_hypervisor_callback[];
 extern const char xen_failsafe_callback[];
 
+extern void *xen_initial_gdt;
+
 struct trap_info;
 void xen_copy_trap_info(struct trap_info *traps);