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/kernel/entry_32.S b/arch/x86/kernel/entry_32.S
index 568c6cc..5d80d53 100644
--- a/arch/x86/kernel/entry_32.S
+++ b/arch/x86/kernel/entry_32.S
@@ -1017,6 +1017,13 @@
ENDPROC(kernel_thread_helper)
#ifdef CONFIG_XEN
+/* Xen doesn't set %esp to be precisely what the normal sysenter
+ entrypoint expects, so fix it up before using the normal path. */
+ENTRY(xen_sysenter_target)
+ RING0_INT_FRAME
+ addl $5*4, %esp /* remove xen-provided frame */
+ jmp sysenter_past_esp
+
ENTRY(xen_hypervisor_callback)
CFI_STARTPROC
pushl $0
@@ -1036,8 +1043,17 @@
jae 1f
call xen_iret_crit_fixup
+ jmp 2f
-1: mov %esp, %eax
+1: cmpl $xen_sysexit_start_crit,%eax
+ jb 2f
+ cmpl $xen_sysexit_end_crit,%eax
+ jae 2f
+
+ jmp xen_sysexit_crit_fixup
+
+ENTRY(xen_do_upcall)
+2: mov %esp, %eax
call xen_evtchn_do_upcall
jmp ret_from_intr
CFI_ENDPROC