illumos gate

When using DTrace to understand KVM performance, it's very useful to be able to pull out VM registers from the current VMCS. Like uregs[], this is a DTrace-defined associative array, with indices specified by the constants specified by the architecture. This allows for DTrace one-liners like:

# dtrace -n kvm-guest-exit'{@[pid, vmregs[VMX_GUEST_RIP]] = count()}' -n tick-1sec'{printf("%10s %20s %s\n", "PID", "GUEST RIP", "COUNT"); printa("%10d %20x %@d\n", @); clear(@); }' -q

       PID            GUEST RIP COUNT
      5026             fee61bc4 0
      5026     fffffffffb8ba740 0
      4668     ffffffff8100a72d 1
      5026             fe931ace 1
      5026     fffffffffb84d9c1 1
      5026     fffffffffb84d9cd 1
      5026     fffffffffb84da03 1
      5026     fffffffffb84da0f 1
      5026     fffffffffb84db0c 1
      5026     fffffffffb84db18 1
      5026     fffffffffb84db73 1
      5026     fffffffffb84db7f 1
      4668     ffffffff81031afa 2
      4668     ffffffff81031b0a 2
      4668     ffffffff81031b1f 2
      4668     ffffffff814c753f 2
      5026     fffffffff794c158 2
      5026     fffffffff794d0e6 2
      5026     fffffffff794d15a 2
      5026     fffffffff794d168 2
      5026     fffffffffb84dae2 2
      5026     fffffffffb84daee 2
      5026     fffffffffb84da49 3
      5026     fffffffffb84da55 3
      5026     fffffffffb84da6b 3
      5026     fffffffffb84da77 3
      5026     fffffffffb84da8e 3
      5026     fffffffffb84da9a 3
      5026     fffffffffb84dab1 3
      5026     fffffffffb84dabd 3
      4668     ffffffff81037f0a 12
      4668     ffffffff8103163b 26
      5026     fffffffff794c074 119
      5026     fffffffffb84072d 121
      5026     fffffffff794d10a 137
^C