[IA64] Make gp value point to the xenva area in mca handler

backport the c/s f5a3f3dc189485d607fbd42678cc23958acc0a6e
of linux.
Xen/ia64 vmm is also relocatable so that it doesn't
lay in the identity mapping area.

Signed-off-by: Isaku Yamahata <yamahata@xxxxxxxxxxxxx>

diff -r 56fd65561b69 xen/include/asm-ia64/linux-xen/asm/mca_asm.h
--- a/xen/include/asm-ia64/linux-xen/asm/mca_asm.h	Wed Aug 13 17:07:13 2008 +0900
+++ b/xen/include/asm-ia64/linux-xen/asm/mca_asm.h	Wed Aug 13 17:18:49 2008 +0900
@@ -198,6 +198,59 @@
  *	7.	Do an rfi to move ipsr to psr and iip to ip.
  */
 
+#ifdef XEN
+#define VIRTUAL_MODE_ENTER(temp1, temp2, start_addr, old_psr)	\
+	mov	temp2 = psr;					\
+	;;							\
+	mov	old_psr = temp2;				\
+	;;							\
+	dep	temp2 = 0, temp2, PSR_IC, 2;			\
+	;;							\
+	mov	psr.l = temp2;					\
+	mov	ar.rsc = 0;					\
+	;;							\
+	srlz.d;							\
+	mov	r13 = ar.k6;					\
+	mov	temp2 = ar.bspstore;				\
+	;;							\
+	DATA_PA_TO_VA(temp2,temp1);				\
+	;;							\
+	mov	temp1 = ar.rnat;				\
+	;;							\
+	mov	ar.bspstore = temp2;				\
+	;;							\
+	mov	ar.rnat = temp1;				\
+	;;							\
+	mov	temp1 = old_psr;				\
+	;;							\
+	mov	temp2 = 1;					\
+	;;							\
+	dep	temp1 = temp2, temp1, PSR_IC, 1;		\
+	;;							\
+	dep	temp1 = temp2, temp1, PSR_IT, 1;		\
+	;;							\
+	dep	temp1 = temp2, temp1, PSR_DT, 1;		\
+	;;							\
+	dep	temp1 = temp2, temp1, PSR_RT, 1;		\
+	;;							\
+	dep	temp1 = temp2, temp1, PSR_BN, 1;		\
+	;;							\
+								\
+	mov     cr.ipsr = temp1;				\
+	movl	temp2 = start_addr;				\
+	;;							\
+	mov	cr.iip = temp2;					\
+	movl	gp = __gp;					\
+	;;							\
+	DATA_PA_TO_VA(sp, temp1);				\
+	srlz.i;							\
+	;;							\
+	nop	1;						\
+	nop	2;						\
+	nop	1;						\
+	rfi							\
+	;;
+#else
 #define VIRTUAL_MODE_ENTER(temp1, temp2, start_addr, old_psr)	\
 	mov	temp2 = psr;					\
 	;;							\
@@ -249,6 +302,7 @@
 	nop	1;						\
 	rfi							\
 	;;
+#endif
 
 /*
  * The following offsets capture the order in which the