modification of code found at: http://www.linux-kvm.org/page/Enable_VT-X_on_Mac_Pro_%28Early_2008%29 to support FreeBSD

vtxenable.c

#include <sys/types.h>
#include <sys/stat.h>
#include <sys/cpuctl.h>
#include <fcntl.h>

#include <unistd.h>
#include <stdio.h>

/* Returns 1 if processor found, 0 otherwise */

int setupCpu(int cpuid)
{
 int addr = 0x3a; // VTX enable                                                                                                                               

 char devfile[255];
 char kernmod[255];
#ifdef __FreeBSD__
 sprintf(devfile, "/dev/cpuctl%d", cpuid);
 sprintf(kernmod, "cpuctl");
#elif __linux__
 sprintf(devfile, "/dev/cpu/%d/msr", cpuid);
 sprintf(kernmod, "msr");
#endif

 int fd = open(devfile, O_RDONLY);
 if (fd==-1)
 {
   printf("\nDevice %s does not exist.\nEither we have run out of processors, or the %s kernel module is not loaded\n", devfile, kernmod);
   return 0;
}

 char buf[8];

 printf("Checking cpu %d - %s ... ",cpuid, devfile);

 lseek(fd, addr, SEEK_SET);
 read(fd, buf, 8);

 char bLo = buf[0]; // Low byte                                                                                                                               
 if (bLo & 1) // locked                                                                                                                                       
 {
   if (bLo & 4)
     printf("locked ON\n");
   else
     printf("locked OFF\n");
 }
 else
 {  // Unlocked - we can try and turn vtx on                                                                                                                  
   fd = open(devfile, O_WRONLY);
   if (fd == -1)
   {
     printf("Failed to open device for writing\n");
   }
   else
   {
     buf[0] = buf[0] | 5; // On + lock                                                                                                                        
     lseek(fd, addr, SEEK_SET);
     if (write(fd, buf, 8) < 0)
     {
       printf("Failed to write to device\n");
     }
     else
     {
       printf("Switched VT-X on\n");
     }
   }
 }

 return 1;
}

int main(int argc, char *argv[])
{
 printf("MSR Magic 1.0 (C) 2009 George Styles www.georgestyles.co.uk\n");
 printf("FreeBSD support by Mike 'Fuzzy' Partin <[email protected]>\n\n");
 int iCpu = 0;
 while (setupCpu(iCpu) != 0)
 {
   iCpu++;
 }
 return 0;
}