3832 AMD E721 workaround panics on KVM
Reviewed by: Marcel Telka <marcel@telka.sk>

*** 26,35 ****
--- 26,36 ----
   * Copyright (c) 2010, Intel Corporation.
   * All rights reserved.
   */
  /*
   * Copyright (c) 2012, Joyent, Inc.  All rights reserved.
+  * Copyright 2013 Nexenta Systems, Inc.  All rights reserved.
   */
  
  #include <sys/types.h>
  #include <sys/thread.h>
  #include <sys/cpuvar.h>
*** 75,84 ****
--- 76,86 ----
  #include <sys/sysmacros.h>
  #if defined(__xpv)
  #include <sys/hypervisor.h>
  #endif
  #include <sys/cpu_module.h>
+ #include <sys/ontrap.h>
  
  struct cpu      cpus[1];                        /* CPU data */
  struct cpu      *cpu[NCPU] = {&cpus[0]};        /* pointers to all CPUs */
  struct cpu      *cpu_free_list;                 /* list for released CPUs */
  cpu_core_t      cpu_core[NCPU];                 /* cpu_core structures */
*** 1184,1194 ****
  
          missing += do_erratum_298(cpu);
  
          if (cpuid_opteron_erratum(cpu, 721) > 0) {
  #if defined(OPTERON_ERRATUM_721)
!                 wrmsr(MSR_AMD_DE_CFG, rdmsr(MSR_AMD_DE_CFG) | AMD_DE_CFG_E721);
                  opteron_erratum_721++;
  #else
                  workaround_warning(cpu, 721);
                  missing++;
  #endif
--- 1186,1202 ----
  
          missing += do_erratum_298(cpu);
  
          if (cpuid_opteron_erratum(cpu, 721) > 0) {
  #if defined(OPTERON_ERRATUM_721)
!                 on_trap_data_t otd;
! 
!                 if (!on_trap(&otd, OT_DATA_ACCESS))
!                         wrmsr(MSR_AMD_DE_CFG,
!                             rdmsr(MSR_AMD_DE_CFG) | AMD_DE_CFG_E721);
!                 no_trap();
! 
                  opteron_erratum_721++;
  #else
                  workaround_warning(cpu, 721);
                  missing++;
  #endif