/* virt-what-cpuid-helper: Are we running inside KVM or Xen HVM?
- * Copyright (C) 2008 Red Hat Inc.
+ * Copyright (C) 2008-2019 Red Hat Inc.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
*/
#include <stdio.h>
+#include <stdlib.h>
+#include <stdint.h>
#include <string.h>
#if defined(__i386__) || defined(__x86_64__)
-void
-cpu_sig (char *sig)
+
+/* Known x86 hypervisor signatures. Note that if you add a new test
+ * to virt-what.in you may need to update this list. The signature is
+ * always 12 bytes except in the case of KVM.
+ */
+static int
+known_signature (char *sig)
+{
+ return
+ strcmp (sig, "bhyve bhyve ") == 0 ||
+ strcmp (sig, "KVMKVMKVM") == 0 ||
+ strcmp (sig, "LKVMLKVMLKVM") == 0 ||
+ strcmp (sig, "Microsoft Hv") == 0 ||
+ strcmp (sig, "OpenBSDVMM58") == 0 ||
+ strcmp (sig, "TCGTCGTCGTCG") == 0 ||
+ strcmp (sig, "VMwareVMware") == 0 ||
+ strcmp (sig, "XenVMMXenVMM") == 0 ||
+ 0;
+}
+
+static uint32_t
+cpuid (uint32_t eax, char *sig)
{
- unsigned int eax = 0x40000000;
- unsigned int *sig32 = (unsigned int *)sig;
+ uint32_t *sig32 = (uint32_t *) sig;
+
asm volatile (
- "xor %%ebx, %%ebx; cpuid"
- : "=a" (eax), "=b" (sig32[0]), "=c" (sig32[1]), "=d" (sig32[2])
+ "xchgl %%ebx,%1; xor %%ebx,%%ebx; cpuid; xchgl %%ebx,%1"
+ : "=a" (eax), "+r" (sig32[0]), "=c" (sig32[1]), "=d" (sig32[2])
: "0" (eax));
sig[12] = 0;
+
+ return eax;
+}
+
+static void
+cpu_sig (void)
+{
+ char sig[13];
+ const uint32_t base = 0x40000000;
+ uint32_t leaf;
+
+ /* Most hypervisors only have information in leaf 0x40000000.
+ *
+ * Some hypervisors have "Viridian [HyperV] extensions", and those
+ * must appear in slot 0x40000000, but they will also have the true
+ * hypervisor in a higher slot.
+ *
+ * CPUID is supposed to return the maximum leaf offset in %eax, but
+ * this is not reliable. Instead we check the returned signatures
+ * against a known list (the others will be empty or garbage) and
+ * only print the ones we know about. This is OK because if we add
+ * a new test in virt-what we can update the list.
+ *
+ * By searching backwards we only print the highest entry, thus
+ * ignoring Viridian for Xen (and Nutanix). If we ever encounter a
+ * hypervisor that has more than 2 entries we may need to revisit
+ * this.
+ */
+ for (leaf = base + 0xff00; leaf >= base; leaf -= 0x100) {
+ memset (sig, 0, sizeof sig);
+ cpuid (leaf, sig);
+ if (known_signature (sig)) {
+ puts (sig);
+ break;
+ }
+ }
}
-#else
-void
-cpu_sig (char *sig)
+
+#else /* !i386, !x86_64 */
+
+static void
+cpu_sig (void)
{
/* nothing for other architectures */
}
+
#endif
int
main()
{
- char sig[13];
-
- memset (sig, 0, sizeof sig);
-
- cpu_sig (sig);
-
- puts (sig);
- /* Possible values:
- * KVMKVMKVM KVM guest
- * XenVMMXenVMM Xen HVM guest
- * VMwareVMware VMware guest
- */
-
+ cpu_sig ();
return 0;
}