11584 ::xcall would be useful
Reviewed by: Jerry Jelinek <jerry.jelinek@joyent.com>
Reviewed by: Robert Mustacchi <rm@joyent.com>

@@ -150,19 +150,20 @@
  * page-tables, and hence must be page-aligned and page-sized. See
  * hat_pcp_setup().
  *
  * There are CTASSERTs in os/intr.c that verify this all works out.
  */
-#define MACHCPU_SIZE    (1568 + 688)
+#define MACHCPU_SIZE    (1568 + 696)
 #define MACHCPU_PAD     (MMU_PAGESIZE - MACHCPU_SIZE)
 #define MACHCPU_PAD2    (MMU_PAGESIZE - 16 - 3 * sizeof (struct kpti_frame))
 
 struct  machcpu {
         /*
          * x_call fields - used for interprocessor cross calls
          */
         struct xc_msg   *xc_msgbox;
+        struct xc_msg   *xc_curmsg;
         struct xc_msg   *xc_free;
         xc_data_t       xc_data;
         uint32_t        xc_wait_cnt;
         volatile uint32_t xc_work_cnt;