Checking whether an OS is in a virtualized environment

The hypervisor provides a mechanism for an OS to determine if it is running in a virtualized environment and in particular, a QNX hypervisor environment.

ARM platforms

On ARM platforms, check the model property in the Flattened Device Tree (FDT) that describes the underlying system. If this property is set with QVM-v8A, then the OS is hosted in a QNX hypervisor VM (i.e., it is a guest OS).

You can obtain the VMID through the vdev API; for details, refer to the qvm_guest_vmid() entry in the Virtual Device Developer's API Reference which is available in our GitLab repository at https://gitlab.com/qnx/hypervisor.

x86 platforms

For x86 platforms, see your hardware documentation to learn which CPUID register bit your OS needs to check to know if it is running in a hypervisor, and where in the register it needs to look for the VM ID string. The ID string for QNX hypervisor VMs is QNXQVMBS.

Below is an example of C code that a QNX OS might use to check if it is running in a QNX hypervisor: 
#include <stdio.h>
#include <stdint.h>
#include <string.h>
#include <arpa/inet.h>

int cpuid(uint32_t id, uint32_t *regs) {
    asm volatile ("cpuid"
        : "=a" (regs[0]), "=b" (regs[1]), "=c" (regs[2]), "=d" (regs[3])
        : "a" (id), "c" (0));
    return 0;
}

static const char * const qnxstr = "QNXQVMBS";

int main(int argc, char *argv[])
{
    uint32_t regs[4];

    cpuid(1, regs);
    if ((regs[2] & (1 << 31)) == 0) {
        puts("We are not running in a hypervisor");
        return 1; /* not a hypervisor */
    }

    /* It is a hypervisor, but is it OUR hypervisor? */
    cpuid(0x40000000, regs);
    regs[1] = htonl(regs[1]);
    regs[2] = htonl(regs[2]);
    if (memcmp(&regs[1], qnxstr, 4) != 0 || 
          memcmp(&regs[2], qnxstr + 4, 4) != 0) {
        puts("This is a hypervisor but not a QNX hypervisor system");
        return 1; /* not ours :( */
    }

    /* It is a QNX hypervisor. */
    puts("This is a QNX QVM hypervisor system");

    return 0;
}

Linux and Android

You can adapt the C code above for Linux and Android on x86, or run the cpuid utility.

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