1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef ARCH_X86_KVM_REVERSE_CPUID_H
3 #define ARCH_X86_KVM_REVERSE_CPUID_H
4
5 #include <uapi/asm/kvm.h>
6 #include <asm/cpufeature.h>
7 #include <asm/cpufeatures.h>
8
9 /*
10 * Hardware-defined CPUID leafs that are scattered in the kernel, but need to
11 * be directly used by KVM. Note, these word values conflict with the kernel's
12 * "bug" caps, but KVM doesn't use those.
13 */
14 enum kvm_only_cpuid_leafs {
15 CPUID_12_EAX = NCAPINTS,
16 NR_KVM_CPU_CAPS,
17
18 NKVMCAPINTS = NR_KVM_CPU_CAPS - NCAPINTS,
19 };
20
21 #define KVM_X86_FEATURE(w, f) ((w)*32 + (f))
22
23 /* Intel-defined SGX sub-features, CPUID level 0x12 (EAX). */
24 #define KVM_X86_FEATURE_SGX1 KVM_X86_FEATURE(CPUID_12_EAX, 0)
25 #define KVM_X86_FEATURE_SGX2 KVM_X86_FEATURE(CPUID_12_EAX, 1)
26
27 struct cpuid_reg {
28 u32 function;
29 u32 index;
30 int reg;
31 };
32
33 static const struct cpuid_reg reverse_cpuid[] = {
34 [CPUID_1_EDX] = { 1, 0, CPUID_EDX},
35 [CPUID_8000_0001_EDX] = {0x80000001, 0, CPUID_EDX},
36 [CPUID_8086_0001_EDX] = {0x80860001, 0, CPUID_EDX},
37 [CPUID_1_ECX] = { 1, 0, CPUID_ECX},
38 [CPUID_C000_0001_EDX] = {0xc0000001, 0, CPUID_EDX},
39 [CPUID_8000_0001_ECX] = {0x80000001, 0, CPUID_ECX},
40 [CPUID_7_0_EBX] = { 7, 0, CPUID_EBX},
41 [CPUID_D_1_EAX] = { 0xd, 1, CPUID_EAX},
42 [CPUID_8000_0008_EBX] = {0x80000008, 0, CPUID_EBX},
43 [CPUID_6_EAX] = { 6, 0, CPUID_EAX},
44 [CPUID_8000_000A_EDX] = {0x8000000a, 0, CPUID_EDX},
45 [CPUID_7_ECX] = { 7, 0, CPUID_ECX},
46 [CPUID_8000_0007_EBX] = {0x80000007, 0, CPUID_EBX},
47 [CPUID_7_EDX] = { 7, 0, CPUID_EDX},
48 [CPUID_7_1_EAX] = { 7, 1, CPUID_EAX},
49 [CPUID_12_EAX] = {0x00000012, 0, CPUID_EAX},
50 [CPUID_8000_001F_EAX] = {0x8000001f, 0, CPUID_EAX},
51 };
52
53 /*
54 * Reverse CPUID and its derivatives can only be used for hardware-defined
55 * feature words, i.e. words whose bits directly correspond to a CPUID leaf.
56 * Retrieving a feature bit or masking guest CPUID from a Linux-defined word
57 * is nonsensical as the bit number/mask is an arbitrary software-defined value
58 * and can't be used by KVM to query/control guest capabilities. And obviously
59 * the leaf being queried must have an entry in the lookup table.
60 */
reverse_cpuid_check(unsigned int x86_leaf)61 static __always_inline void reverse_cpuid_check(unsigned int x86_leaf)
62 {
63 BUILD_BUG_ON(x86_leaf == CPUID_LNX_1);
64 BUILD_BUG_ON(x86_leaf == CPUID_LNX_2);
65 BUILD_BUG_ON(x86_leaf == CPUID_LNX_3);
66 BUILD_BUG_ON(x86_leaf == CPUID_LNX_4);
67 BUILD_BUG_ON(x86_leaf >= ARRAY_SIZE(reverse_cpuid));
68 BUILD_BUG_ON(reverse_cpuid[x86_leaf].function == 0);
69 }
70
71 /*
72 * Translate feature bits that are scattered in the kernel's cpufeatures word
73 * into KVM feature words that align with hardware's definitions.
74 */
__feature_translate(int x86_feature)75 static __always_inline u32 __feature_translate(int x86_feature)
76 {
77 if (x86_feature == X86_FEATURE_SGX1)
78 return KVM_X86_FEATURE_SGX1;
79 else if (x86_feature == X86_FEATURE_SGX2)
80 return KVM_X86_FEATURE_SGX2;
81
82 return x86_feature;
83 }
84
__feature_leaf(int x86_feature)85 static __always_inline u32 __feature_leaf(int x86_feature)
86 {
87 return __feature_translate(x86_feature) / 32;
88 }
89
90 /*
91 * Retrieve the bit mask from an X86_FEATURE_* definition. Features contain
92 * the hardware defined bit number (stored in bits 4:0) and a software defined
93 * "word" (stored in bits 31:5). The word is used to index into arrays of
94 * bit masks that hold the per-cpu feature capabilities, e.g. this_cpu_has().
95 */
__feature_bit(int x86_feature)96 static __always_inline u32 __feature_bit(int x86_feature)
97 {
98 x86_feature = __feature_translate(x86_feature);
99
100 reverse_cpuid_check(x86_feature / 32);
101 return 1 << (x86_feature & 31);
102 }
103
104 #define feature_bit(name) __feature_bit(X86_FEATURE_##name)
105
x86_feature_cpuid(unsigned int x86_feature)106 static __always_inline struct cpuid_reg x86_feature_cpuid(unsigned int x86_feature)
107 {
108 unsigned int x86_leaf = __feature_leaf(x86_feature);
109
110 reverse_cpuid_check(x86_leaf);
111 return reverse_cpuid[x86_leaf];
112 }
113
__cpuid_entry_get_reg(struct kvm_cpuid_entry2 * entry,u32 reg)114 static __always_inline u32 *__cpuid_entry_get_reg(struct kvm_cpuid_entry2 *entry,
115 u32 reg)
116 {
117 switch (reg) {
118 case CPUID_EAX:
119 return &entry->eax;
120 case CPUID_EBX:
121 return &entry->ebx;
122 case CPUID_ECX:
123 return &entry->ecx;
124 case CPUID_EDX:
125 return &entry->edx;
126 default:
127 BUILD_BUG();
128 return NULL;
129 }
130 }
131
cpuid_entry_get_reg(struct kvm_cpuid_entry2 * entry,unsigned int x86_feature)132 static __always_inline u32 *cpuid_entry_get_reg(struct kvm_cpuid_entry2 *entry,
133 unsigned int x86_feature)
134 {
135 const struct cpuid_reg cpuid = x86_feature_cpuid(x86_feature);
136
137 return __cpuid_entry_get_reg(entry, cpuid.reg);
138 }
139
cpuid_entry_get(struct kvm_cpuid_entry2 * entry,unsigned int x86_feature)140 static __always_inline u32 cpuid_entry_get(struct kvm_cpuid_entry2 *entry,
141 unsigned int x86_feature)
142 {
143 u32 *reg = cpuid_entry_get_reg(entry, x86_feature);
144
145 return *reg & __feature_bit(x86_feature);
146 }
147
cpuid_entry_has(struct kvm_cpuid_entry2 * entry,unsigned int x86_feature)148 static __always_inline bool cpuid_entry_has(struct kvm_cpuid_entry2 *entry,
149 unsigned int x86_feature)
150 {
151 return cpuid_entry_get(entry, x86_feature);
152 }
153
cpuid_entry_clear(struct kvm_cpuid_entry2 * entry,unsigned int x86_feature)154 static __always_inline void cpuid_entry_clear(struct kvm_cpuid_entry2 *entry,
155 unsigned int x86_feature)
156 {
157 u32 *reg = cpuid_entry_get_reg(entry, x86_feature);
158
159 *reg &= ~__feature_bit(x86_feature);
160 }
161
cpuid_entry_set(struct kvm_cpuid_entry2 * entry,unsigned int x86_feature)162 static __always_inline void cpuid_entry_set(struct kvm_cpuid_entry2 *entry,
163 unsigned int x86_feature)
164 {
165 u32 *reg = cpuid_entry_get_reg(entry, x86_feature);
166
167 *reg |= __feature_bit(x86_feature);
168 }
169
cpuid_entry_change(struct kvm_cpuid_entry2 * entry,unsigned int x86_feature,bool set)170 static __always_inline void cpuid_entry_change(struct kvm_cpuid_entry2 *entry,
171 unsigned int x86_feature,
172 bool set)
173 {
174 u32 *reg = cpuid_entry_get_reg(entry, x86_feature);
175
176 /*
177 * Open coded instead of using cpuid_entry_{clear,set}() to coerce the
178 * compiler into using CMOV instead of Jcc when possible.
179 */
180 if (set)
181 *reg |= __feature_bit(x86_feature);
182 else
183 *reg &= ~__feature_bit(x86_feature);
184 }
185
186 #endif /* ARCH_X86_KVM_REVERSE_CPUID_H */
187