KVM: Limit vcpu mmap size to one page on non-x86

The second page is only needed on archs that support pio.

Noted by Carsten Otte.

Signed-off-by: Avi Kivity <avi@qumranet.com>
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 121e65c..7972e3a 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1061,7 +1061,10 @@
 		r = -EINVAL;
 		if (arg)
 			goto out;
-		r = 2 * PAGE_SIZE;
+		r = PAGE_SIZE;     /* struct kvm_run */
+#ifdef CONFIG_X86
+		r += PAGE_SIZE;    /* pio data page */
+#endif
 		break;
 	default:
 		return kvm_arch_dev_ioctl(filp, ioctl, arg);