x86: split loading percpu segments from loading gdt
Impact: split out a function, no functional change
Xen needs to be able to access percpu data from very early on. For
various reasons, it cannot also load the gdt at that time. It does,
however, have a pefectly functional gdt at that point, so there's no
pressing need to reload the gdt.
Split the function to load the segment registers off, so Xen can call
it directly.
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 6eacd64..0f73ea4 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -253,6 +253,16 @@
__u32 cleared_cpu_caps[NCAPINTS] __cpuinitdata;
+void load_percpu_segment(int cpu)
+{
+#ifdef CONFIG_X86_32
+ loadsegment(fs, __KERNEL_PERCPU);
+#else
+ loadsegment(gs, 0);
+ wrmsrl(MSR_GS_BASE, (unsigned long)per_cpu(irq_stack_union.gs_base, cpu));
+#endif
+}
+
/* Current gdt points %fs at the "master" per-cpu area: after this,
* it's on the real one. */
void switch_to_new_gdt(int cpu)
@@ -263,12 +273,8 @@
gdt_descr.size = GDT_SIZE - 1;
load_gdt(&gdt_descr);
/* Reload the per-cpu base */
-#ifdef CONFIG_X86_32
- loadsegment(fs, __KERNEL_PERCPU);
-#else
- loadsegment(gs, 0);
- wrmsrl(MSR_GS_BASE, (unsigned long)per_cpu(irq_stack_union.gs_base, cpu));
-#endif
+
+ load_percpu_segment(cpu);
}
static struct cpu_dev *cpu_devs[X86_VENDOR_NUM] = {};