x86/paravirt, 64-bit: add adjust_exception_frame

64-bit Xen pushes a couple of extra words onto an exception frame.
Add a hook to deal with them.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Cc: xen-devel <xen-devel@lists.xensource.com>
Cc: Stephen Tweedie <sct@redhat.com>
Cc: Eduardo Habkost <ehabkost@redhat.com>
Cc: Mark McLoughlin <markmc@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/include/asm-x86/paravirt.h b/include/asm-x86/paravirt.h
index 3286a0c..3dc223d 100644
--- a/include/asm-x86/paravirt.h
+++ b/include/asm-x86/paravirt.h
@@ -189,6 +189,10 @@
 	void (*irq_enable)(void);
 	void (*safe_halt)(void);
 	void (*halt)(void);
+
+#ifdef CONFIG_X86_64
+	void (*adjust_exception_frame)(void);
+#endif
 };
 
 struct pv_apic_ops {
@@ -1544,6 +1548,11 @@
 	movq %rax, %rcx;				\
 	xorq %rax, %rax;
 
+#define PARAVIRT_ADJUST_EXCEPTION_FRAME					\
+	PARA_SITE(PARA_PATCH(pv_irq_ops, PV_IRQ_adjust_exception_frame), \
+		  CLBR_NONE,						\
+		  call PARA_INDIRECT(pv_irq_ops+PV_IRQ_adjust_exception_frame))
+
 #define USERGS_SYSRET64							\
 	PARA_SITE(PARA_PATCH(pv_cpu_ops, PV_CPU_usergs_sysret64),	\
 		  CLBR_NONE,						\