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/setup.c b/arch/x86/xen/setup.c
index 2341492..82517e4 100644
--- a/arch/x86/xen/setup.c
+++ b/arch/x86/xen/setup.c
@@ -16,6 +16,7 @@
#include <asm/xen/hypervisor.h>
#include <asm/xen/hypercall.h>
+#include <xen/interface/callback.h>
#include <xen/interface/physdev.h>
#include <xen/features.h>
@@ -68,6 +69,24 @@
*mask |= 1 << VDSO_NOTE_NONEGSEG_BIT;
}
+void xen_enable_sysenter(void)
+{
+ int cpu = smp_processor_id();
+ extern void xen_sysenter_target(void);
+ /* Mask events on entry, even though they get enabled immediately */
+ static struct callback_register sysenter = {
+ .type = CALLBACKTYPE_sysenter,
+ .address = { __KERNEL_CS, (unsigned long)xen_sysenter_target },
+ .flags = CALLBACKF_mask_events,
+ };
+
+ if (!boot_cpu_has(X86_FEATURE_SEP) ||
+ HYPERVISOR_callback_op(CALLBACKOP_register, &sysenter) != 0) {
+ clear_cpu_cap(&cpu_data(cpu), X86_FEATURE_SEP);
+ clear_cpu_cap(&boot_cpu_data, X86_FEATURE_SEP);
+ }
+}
+
void __init xen_arch_setup(void)
{
struct physdev_set_iopl set_iopl;
@@ -82,6 +101,8 @@
HYPERVISOR_set_callbacks(__KERNEL_CS, (unsigned long)xen_hypervisor_callback,
__KERNEL_CS, (unsigned long)xen_failsafe_callback);
+ xen_enable_sysenter();
+
set_iopl.iopl = 1;
rc = HYPERVISOR_physdev_op(PHYSDEVOP_set_iopl, &set_iopl);
if (rc != 0)