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

*** 150,168 ****
   * 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_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_free;
          xc_data_t       xc_data;
          uint32_t        xc_wait_cnt;
          volatile uint32_t xc_work_cnt;
  
--- 150,169 ----
   * 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 + 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;