Detect Virtual Machine

Fix #90

libcpuid/cpuid_main.c

@@ -568,6 +568,7 @@ static void load_features_common(struct cpu_raw_data_t* raw, struct cpu_id_t* da
 		{ 28, CPU_FEATURE_AVX },
 		{ 29, CPU_FEATURE_F16C },
 		{ 30, CPU_FEATURE_RDRAND },
+		{ 31, CPU_FEATURE_HYPERVISOR },
 	};
 	const struct feature_map_t matchtable_ebx7[] = {
 		{  3, CPU_FEATURE_BMI1 },
@@ -1180,6 +1181,7 @@ const char* cpu_feature_str(cpu_feature_t feature)
 		{ CPU_FEATURE_AVX512VNNI, "avx512vnni" },
 		{ CPU_FEATURE_AVX512VBMI, "avx512vbmi" },
 		{ CPU_FEATURE_AVX512VBMI2, "avx512vbmi2" },
+		{ CPU_FEATURE_HYPERVISOR, "hypervisor" },
 	};
 	unsigned i, n = COUNT_OF(matchtable);
 	if (n != NUM_CPU_FEATURES) {
@@ -1299,6 +1301,65 @@ void cpuid_get_cpu_list(cpu_vendor_t vendor, struct cpu_list_t* list)
  	}
 }
 
+hypervisor_vendor_t cpuid_get_hypervisor(struct cpu_raw_data_t* raw, struct cpu_id_t* data)
+{
+	int i, r;
+	uint32_t hypervisor_fn40000000h[NUM_REGS];
+	char hypervisor_str[VENDOR_STR_MAX];
+	struct cpu_id_t mydata;
+	const struct { hypervisor_vendor_t hypervisor; char match[16]; }
+	matchtable[NUM_HYPERVISOR_VENDORS] = {
+		/* source: https://github.com/a0rtega/pafish/blob/master/pafish/cpu.c */
+		{ HYPERVISOR_BHYVE      , "bhyve bhyve\0"   },
+		{ HYPERVISOR_HYPERV     , "Microsoft Hv"    },
+		{ HYPERVISOR_KVM        , "KVMKVMKVM\0\0\0" },
+		{ HYPERVISOR_PARALLELS  , "prl hyperv\0\0"  },
+		{ HYPERVISOR_QEMU       , "TCGTCGTCGTCG"    },
+		{ HYPERVISOR_VIRTUALBOX , "VBoxVBoxVBox"    },
+		{ HYPERVISOR_VMWARE     , "VMwareVMware"    },
+		{ HYPERVISOR_XEN        , "XenVMMXenVMM"    },
+	};
+
+	if (!data) {
+		if ((r = cpu_identify(raw, data)) < 0)
+			return HYPERVISOR_UNKNOWN;
+		data = &mydata;
+	}
+
+	/* Intel and AMD CPUs have reserved bit 31 of ECX of CPUID leaf 0x1 as the hypervisor present bit
+	Source: https://kb.vmware.com/s/article/1009458 */
+	switch (data->vendor) {
+		case VENDOR_AMD:
+		case VENDOR_INTEL:
+			break;
+		default:
+			return HYPERVISOR_UNKNOWN;
+	}
+	if (!data->flags[CPU_FEATURE_HYPERVISOR])
+		return HYPERVISOR_NONE;
+
+	/* Intel and AMD have also reserved CPUID leaves 0x40000000 - 0x400000FF for software use.
+	Hypervisors can use these leaves to provide an interface to pass information
+	from the hypervisor to the guest operating system running inside a virtual machine.
+	The hypervisor bit indicates the presence of a hypervisor
+	and that it is safe to test these additional software leaves. */
+	memset(hypervisor_fn40000000h, 0, sizeof(hypervisor_fn40000000h));
+	hypervisor_fn40000000h[EAX] = 0x40000000;
+	cpu_exec_cpuid_ext(hypervisor_fn40000000h);
+
+	/* Copy the hypervisor CPUID information leaf */
+	memcpy(hypervisor_str + 0, &hypervisor_fn40000000h[1], 4);
+	memcpy(hypervisor_str + 4, &hypervisor_fn40000000h[2], 4);
+	memcpy(hypervisor_str + 8, &hypervisor_fn40000000h[3], 4);
+	hypervisor_str[12] = '\0';
+
+	/* Determine hypervisor */
+	for (i = 0; i < NUM_HYPERVISOR_VENDORS; i++)
+		if (!strcmp(hypervisor_str, matchtable[i].match))
+			return matchtable[i].hypervisor;
+	return HYPERVISOR_UNKNOWN;
+}
+
 void cpuid_free_cpu_list(struct cpu_list_t* list)
 {
 	int i;

libcpuid/exports.def

@@ -44,3 +44,4 @@ cpuid_free_raw_data_array @40
 affinity_mask_str @41
 cpuid_free_system_id @42
 affinity_mask_str_r @43
+cpuid_get_hypervisor @44

libcpuid/libcpuid.h

@@ -148,6 +148,24 @@ typedef enum {
 } cpu_purpose_t;
 #define NUM_CPU_PURPOSES NUM_CPU_PURPOSES
 
+/**
+ * @brief Hypervisor vendor, as guessed from the CPU_FEATURE_HYPERVISOR flag.
+ */
+typedef enum {
+	HYPERVISOR_NONE = 0,     /*!< no hypervisor */
+	HYPERVISOR_BHYVE,        /*!< FreeBSD bhyve hypervisor */
+	HYPERVISOR_HYPERV,       /*!< Microsoft Hyper-V or Windows Virtual PC hypervisor */
+	HYPERVISOR_KVM,          /*!< KVM hypervisor */
+	HYPERVISOR_PARALLELS,    /*!< Parallels hypervisor */
+	HYPERVISOR_QEMU,         /*!< QEMU hypervisor */
+	HYPERVISOR_VIRTUALBOX,   /*!< VirtualBox hypervisor */
+	HYPERVISOR_VMWARE,       /*!< VMware hypervisor */
+	HYPERVISOR_XEN,          /*!< Xen hypervisor */
+	NUM_HYPERVISOR_VENDORS,  /*!< Valid hypervisor vendor ids: 0..NUM_HYPERVISOR_VENDORS - 1 */
+	HYPERVISOR_UNKNOWN = -1,
+} hypervisor_vendor_t;
+#define NUM_HYPERVISOR_VENDORS NUM_HYPERVISOR_VENDORS
+
 /**
  * @brief Contains just the raw CPUID data.
  *
@@ -591,6 +609,7 @@ typedef enum {
 	CPU_FEATURE_AVX512VNNI, /*!< AVX-512 Vector Neural Network Instructions */
 	CPU_FEATURE_AVX512VBMI, /*!< AVX-512 Vector Bit ManipulationInstructions (version 1) */
 	CPU_FEATURE_AVX512VBMI2, /*!< AVX-512 Vector Bit ManipulationInstructions (version 2) */
+	CPU_FEATURE_HYPERVISOR, /*!< Hypervisor present (always zero on physical CPUs) */
 	/* termination: */
 	NUM_CPU_FEATURES,
 } cpu_feature_t;
@@ -1167,6 +1186,24 @@ void cpuid_set_verbosiness_level(int level);
  */
 cpu_vendor_t cpuid_get_vendor(void);
 
+/**
+ * @brief Obtains the hypervisor vendor from CPUID from the current CPU
+ * @param raw - Optional input - a pointer to the raw CPUID data, which is obtained
+ *              either by cpuid_get_raw_data or cpuid_deserialize_raw_data.
+ *              Can also be NULL, in which case the functions calls
+ *              cpuid_get_raw_data itself.
+ * @param data - Optional input - the decoded CPU features/info is written here.
+ *              Can also be NULL, in which case the functions calls
+ *              cpu_identify itself.
+ * @note If no hypervisor is detected, the hypervisor can be hidden in some cases.
+ *       Refer to https://github.com/anrieff/libcpuid/issues/90#issuecomment-296568713.
+ * @returns HYPERVISOR_UNKNOWN if failed,
+ *          HYPERVISOR_NONE if no hypervisor detected (or hidden),
+ *          otherwise the hypervisor vendor type.
+ *          @see hypervisor_vendor_t
+ */
+hypervisor_vendor_t cpuid_get_hypervisor(struct cpu_raw_data_t* raw, struct cpu_id_t* data);
+
 /**
  * @brief a structure that holds a list of processor names
  */

libcpuid/libcpuid.sym

@@ -41,3 +41,4 @@ cpuid_free_raw_data_array
 affinity_mask_str
 cpuid_free_system_id
 affinity_mask_str_r
+cpuid_get_hypervisor