1 // SPDX-License-Identifier: GPL-2.0
2 
3 /*
4  * Core routines for interacting with Microsoft's Hyper-V hypervisor,
5  * including hypervisor initialization.
6  *
7  * Copyright (C) 2021, Microsoft, Inc.
8  *
9  * Author : Michael Kelley <mikelley@microsoft.com>
10  */
11 
12 #include <linux/types.h>
13 #include <linux/acpi.h>
14 #include <linux/export.h>
15 #include <linux/errno.h>
16 #include <linux/version.h>
17 #include <linux/cpuhotplug.h>
18 #include <asm/mshyperv.h>
19 
20 static bool hyperv_initialized;
21 
22 int hv_get_hypervisor_version(union hv_hypervisor_version_info *info)
23 {
24 	hv_get_vpreg_128(HV_REGISTER_HYPERVISOR_VERSION,
25 			 (struct hv_get_vp_registers_output *)info);
26 
27 	return 0;
28 }
29 EXPORT_SYMBOL_GPL(hv_get_hypervisor_version);
30 
31 #ifdef CONFIG_ACPI
32 
33 static bool __init hyperv_detect_via_acpi(void)
34 {
35 	if (acpi_disabled)
36 		return false;
37 	/*
38 	 * Hypervisor ID is only available in ACPI v6+, and the
39 	 * structure layout was extended in v6 to accommodate that
40 	 * new field.
41 	 *
42 	 * At the very minimum, this check makes sure not to read
43 	 * past the FADT structure.
44 	 *
45 	 * It is also needed to catch running in some unknown
46 	 * non-Hyper-V environment that has ACPI 5.x or less.
47 	 * In such a case, it can't be Hyper-V.
48 	 */
49 	if (acpi_gbl_FADT.header.revision < 6)
50 		return false;
51 	return strncmp((char *)&acpi_gbl_FADT.hypervisor_id, "MsHyperV", 8) == 0;
52 }
53 
54 #else
55 
56 static bool __init hyperv_detect_via_acpi(void)
57 {
58 	return false;
59 }
60 
61 #endif
62 
63 static bool __init hyperv_detect_via_smccc(void)
64 {
65 	uuid_t hyperv_uuid = UUID_INIT(
66 		0x58ba324d, 0x6447, 0x24cd,
67 		0x75, 0x6c, 0xef, 0x8e,
68 		0x24, 0x70, 0x59, 0x16);
69 
70 	return arm_smccc_hypervisor_has_uuid(&hyperv_uuid);
71 }
72 
73 static int __init hyperv_init(void)
74 {
75 	struct hv_get_vp_registers_output	result;
76 	u64	guest_id;
77 	int	ret;
78 
79 	/*
80 	 * Allow for a kernel built with CONFIG_HYPERV to be running in
81 	 * a non-Hyper-V environment.
82 	 *
83 	 * In such cases, do nothing and return success.
84 	 */
85 	if (!hyperv_detect_via_acpi() && !hyperv_detect_via_smccc())
86 		return 0;
87 
88 	/* Setup the guest ID */
89 	guest_id = hv_generate_guest_id(LINUX_VERSION_CODE);
90 	hv_set_vpreg(HV_REGISTER_GUEST_OS_ID, guest_id);
91 
92 	/* Get the features and hints from Hyper-V */
93 	hv_get_vpreg_128(HV_REGISTER_PRIVILEGES_AND_FEATURES_INFO, &result);
94 	ms_hyperv.features = result.as32.a;
95 	ms_hyperv.priv_high = result.as32.b;
96 	ms_hyperv.misc_features = result.as32.c;
97 
98 	hv_get_vpreg_128(HV_REGISTER_FEATURES_INFO, &result);
99 	ms_hyperv.hints = result.as32.a;
100 
101 	pr_info("Hyper-V: privilege flags low 0x%x, high 0x%x, hints 0x%x, misc 0x%x\n",
102 		ms_hyperv.features, ms_hyperv.priv_high, ms_hyperv.hints,
103 		ms_hyperv.misc_features);
104 
105 	hv_identify_partition_type();
106 
107 	ret = hv_common_init();
108 	if (ret)
109 		return ret;
110 
111 	ret = cpuhp_setup_state(CPUHP_AP_HYPERV_ONLINE, "arm64/hyperv_init:online",
112 				hv_common_cpu_init, hv_common_cpu_die);
113 	if (ret < 0) {
114 		hv_common_free();
115 		return ret;
116 	}
117 
118 	if (ms_hyperv.priv_high & HV_ACCESS_PARTITION_ID)
119 		hv_get_partition_id();
120 	ms_hyperv.vtl = get_vtl();
121 	if (ms_hyperv.vtl > 0) /* non default VTL */
122 		pr_info("Linux runs in Hyper-V Virtual Trust Level %d\n", ms_hyperv.vtl);
123 
124 	ms_hyperv_late_init();
125 
126 	hyperv_initialized = true;
127 	return 0;
128 }
129 
130 early_initcall(hyperv_init);
131 
132 bool hv_is_hyperv_initialized(void)
133 {
134 	return hyperv_initialized;
135 }
136 EXPORT_SYMBOL_GPL(hv_is_hyperv_initialized);
137