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/enlighten.c b/arch/x86/xen/enlighten.c
index 36f36e6..9436845 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -155,7 +155,6 @@
if (*ax == 1)
maskedx = ~((1 << X86_FEATURE_APIC) | /* disable APIC */
(1 << X86_FEATURE_ACPI) | /* disable ACPI */
- (1 << X86_FEATURE_SEP) | /* disable SEP */
(1 << X86_FEATURE_ACC)); /* thermal monitoring */
asm(XEN_EMULATE_PREFIX "cpuid"
@@ -994,7 +993,7 @@
.read_pmc = native_read_pmc,
.iret = xen_iret,
- .irq_enable_syscall_ret = NULL, /* never called */
+ .irq_enable_syscall_ret = xen_sysexit,
.load_tr_desc = paravirt_nop,
.set_ldt = xen_set_ldt,