xen: support sysenter/sysexit if hypervisor does
64-bit Xen supports sysenter for 32-bit guests, so support its
use. (sysenter is faster than int $0x80 in 32-on-64.)
sysexit is still not supported, so we fake it up using iret.
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
diff --git a/arch/x86/xen/smp.c b/arch/x86/xen/smp.c
index e340ff9..d61e4f8 100644
--- a/arch/x86/xen/smp.c
+++ b/arch/x86/xen/smp.c
@@ -72,6 +72,7 @@
int cpu = smp_processor_id();
cpu_init();
+ xen_enable_sysenter();
preempt_disable();
per_cpu(cpu_state, cpu) = CPU_ONLINE;