/* 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__)
-static unsigned int
-cpuid (unsigned int eax, 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. Note the
+ * signature is always 12 bytes long, plus we add \0 to the end to
+ * make it 13 bytes.
+ */
+static int
+known_signature (const char *sig)
+{
+ return
+ strcmp (sig, "bhyve bhyve ") == 0 ||
+ memcmp (sig, "KVMKVMKVM\0\0\0", 12) == 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;
+}
+
+/* Copied from the Linux kernel definition in
+ * arch/x86/include/asm/processor.h
+ */
+static inline void
+cpuid (uint32_t *eax, uint32_t *ebx, uint32_t *ecx, uint32_t *edx)
{
- unsigned int *sig32 = (unsigned int *) sig;
+ asm volatile ("cpuid"
+ : "=a" (*eax), "=b" (*ebx), "=c" (*ecx), "=d" (*edx)
+ : "0" (*eax), "2" (*ecx)
+ : "memory");
+}
- asm volatile (
- "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;
+static uint32_t
+cpuid_leaf (uint32_t eax, char *sig)
+{
+ uint32_t *sig32 = (uint32_t *) sig;
+ cpuid (&eax, &sig32[0], &sig32[1], &sig32[2]);
+ sig[12] = 0; /* \0-terminate the string to make string comparison possible */
return eax;
}
cpu_sig (void)
{
char sig[13];
- unsigned int base = 0x40000000, leaf = base;
- unsigned int max_entries;
-
- memset (sig, 0, sizeof sig);
- max_entries = cpuid (leaf, sig);
- puts (sig);
+ const uint32_t base = 0x40000000;
+ uint32_t leaf;
- /* Most hypervisors only have information in leaf 0x40000000, but
- * upstream Xen contains further leaf entries (in particular when
- * used with Viridian [HyperV] extensions). CPUID is supposed to
- * return the maximum leaf offset in %eax, so that's what we use,
- * but only if it looks sensible.
+ /* 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.
*/
- if (max_entries > 3 && max_entries < 0x10000) {
- for (leaf = base + 0x100; leaf <= base + max_entries; leaf += 0x100) {
- memset (sig, 0, sizeof sig);
- cpuid (leaf, sig);
+ for (leaf = base + 0xff00; leaf >= base; leaf -= 0x100) {
+ memset (sig, 0, sizeof sig);
+ cpuid_leaf (leaf, sig);
+ if (known_signature (sig)) {
puts (sig);
+ break;
}
}
}