KVM: PPC: Add PV guest scratch registers

While running in hooked code we need to store register contents out because
we must not clobber any registers.

So let's add some fields to the shared page we can just happily write to.
Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Avi Kivity <avi@redhat.com>

arch/powerpc/include/asm/kvm_para.h

@@ -24,6 +24,9 @@
 #include <linux/of.h>
 
 struct kvm_vcpu_arch_shared {
+	__u64 scratch1;
+	__u64 scratch2;
+	__u64 scratch3;
 	__u64 critical;		/* Guest may not get interrupts if == r1 */
 	__u64 sprg0;
 	__u64 sprg1;