xen: use iret instruction all the time

Change iret implementation to not be dependent on direct-access vcpu
structure.

Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/xen/enlighten.c

@@ -890,7 +890,6 @@ void __init xen_setup_vcpu_info_placement(void)
 		pv_irq_ops.irq_disable = xen_irq_disable_direct;
 		pv_irq_ops.irq_enable = xen_irq_enable_direct;
 		pv_mmu_ops.read_cr2 = xen_read_cr2_direct;
-		pv_cpu_ops.iret = xen_iret_direct;
 	}
 }
 
@@ -994,7 +993,7 @@ static const struct pv_cpu_ops xen_cpu_ops __initdata = {
 	.read_tsc = native_read_tsc,
 	.read_pmc = native_read_pmc,
 
-	.iret = (void *)&hypercall_page[__HYPERVISOR_iret],
+	.iret = xen_iret,
 	.irq_enable_syscall_ret = NULL,  /* never called */
 
 	.load_tr_desc = paravirt_nop,

arch/x86/xen/xen-asm.S

@@ -135,13 +135,8 @@ ENDPATCH(xen_restore_fl_direct)
 	current stack state in whatever form its in, we keep things
 	simple by only using a single register which is pushed/popped
 	on the stack.
-
-	Non-direct iret could be done in the same way, but it would
-	require an annoying amount of code duplication.  We'll assume
-	that direct mode will be the common case once the hypervisor
-	support becomes commonplace.
  */
-ENTRY(xen_iret_direct)
+ENTRY(xen_iret)
 	/* test eflags for special cases */
 	testl $(X86_EFLAGS_VM | XEN_EFLAGS_NMI), 8(%esp)
 	jnz hyper_iret
@@ -155,9 +150,9 @@ ENTRY(xen_iret_direct)
 	GET_THREAD_INFO(%eax)
 	movl TI_cpu(%eax),%eax
 	movl __per_cpu_offset(,%eax,4),%eax
-	lea per_cpu__xen_vcpu_info(%eax),%eax
+	mov per_cpu__xen_vcpu(%eax),%eax
 #else
-	movl $per_cpu__xen_vcpu_info, %eax
+	movl per_cpu__xen_vcpu, %eax
 #endif
 
 	/* check IF state we're restoring */

arch/x86/xen/xen-ops.h

@@ -63,5 +63,5 @@ DECL_ASM(void, xen_irq_disable_direct, void);
 DECL_ASM(unsigned long, xen_save_fl_direct, void);
 DECL_ASM(void, xen_restore_fl_direct, unsigned long);
 
-void xen_iret_direct(void);
+void xen_iret(void);
 #endif /* XEN_OPS_H */