9685 KPTI %cr3 handling needs fixes

*** 364,381 ****
          xc_call(0, 0, 0, CPUSET2BV(cpuset), (xc_func_t)kdi_cpu_deactivate);
          kdi_nmemranges = 0;
  }
  
  /*
!  * We receive all breakpoints and single step traps.  Some of them,
!  * including those from userland and those induced by DTrace providers,
!  * are intended for the kernel, and must be processed there.  We adopt
!  * this ours-until-proven-otherwise position due to the painful
!  * consequences of sending the kernel an unexpected breakpoint or
!  * single step.  Unless someone can prove to us that the kernel is
!  * prepared to handle the trap, we'll assume there's a problem and will
!  * give the user a chance to debug it.
   */
  int
  kdi_trap_pass(kdi_cpusave_t *cpusave)
  {
          greg_t tt = cpusave->krs_gregs[KDIREG_TRAPNO];
--- 364,383 ----
          xc_call(0, 0, 0, CPUSET2BV(cpuset), (xc_func_t)kdi_cpu_deactivate);
          kdi_nmemranges = 0;
  }
  
  /*
!  * We receive all breakpoints and single step traps.  Some of them, including
!  * those from userland and those induced by DTrace providers, are intended for
!  * the kernel, and must be processed there.  We adopt this
!  * ours-until-proven-otherwise position due to the painful consequences of
!  * sending the kernel an unexpected breakpoint or single step.  Unless someone
!  * can prove to us that the kernel is prepared to handle the trap, we'll assume
!  * there's a problem and will give the user a chance to debug it.
!  *
!  * If we return 2, then the calling code should restore the trap-time %cr3: that
!  * is, it really is a kernel-originated trap.
   */
  int
  kdi_trap_pass(kdi_cpusave_t *cpusave)
  {
          greg_t tt = cpusave->krs_gregs[KDIREG_TRAPNO];
*** 388,398 ****
          if (tt != T_BPTFLT && tt != T_SGLSTP)
                  return (0);
  
          if (tt == T_BPTFLT && kdi_dtrace_get_state() ==
              KDI_DTSTATE_DTRACE_ACTIVE)
!                 return (1);
  
          /*
           * See the comments in the kernel's T_SGLSTP handler for why we need to
           * do this.
           */
--- 390,400 ----
          if (tt != T_BPTFLT && tt != T_SGLSTP)
                  return (0);
  
          if (tt == T_BPTFLT && kdi_dtrace_get_state() ==
              KDI_DTSTATE_DTRACE_ACTIVE)
!                 return (2);
  
          /*
           * See the comments in the kernel's T_SGLSTP handler for why we need to
           * do this.
           */