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 [CPUID_8000_0021_EAX] = {0x80000021, 0, CPUID_EAX},
52 };
53
54 /*
55 * Reverse CPUID and its derivatives can only be used for hardware-defined
56 * feature words, i.e. words whose bits directly correspond to a CPUID leaf.
57 * Retrieving a feature bit or masking guest CPUID from a Linux-defined word
58 * is nonsensical as the bit number/mask is an arbitrary software-defined value
59 * and can't be used by KVM to query/control guest capabilities. And obviously
60 * the leaf being queried must have an entry in the lookup table.
61 */
reverse_cpuid_check(unsigned int x86_leaf)62 static __always_inline void reverse_cpuid_check(unsigned int x86_leaf)
63 {
64 BUILD_BUG_ON(x86_leaf == CPUID_LNX_1);
65 BUILD_BUG_ON(x86_leaf == CPUID_LNX_2);
66 BUILD_BUG_ON(x86_leaf == CPUID_LNX_3);
67 BUILD_BUG_ON(x86_leaf == CPUID_LNX_4);
68 BUILD_BUG_ON(x86_leaf >= ARRAY_SIZE(reverse_cpuid));
69 BUILD_BUG_ON(reverse_cpuid[x86_leaf].function == 0);
70 }
71
72 /*
73 * Translate feature bits that are scattered in the kernel's cpufeatures word
74 * into KVM feature words that align with hardware's definitions.
75 */
__feature_translate(int x86_feature)76 static __always_inline u32 __feature_translate(int x86_feature)
77 {
78 if (x86_feature == X86_FEATURE_SGX1)
79 return KVM_X86_FEATURE_SGX1;
80 else if (x86_feature == X86_FEATURE_SGX2)
81 return KVM_X86_FEATURE_SGX2;
82
83 return x86_feature;
84 }
85
__feature_leaf(int x86_feature)86 static __always_inline u32 __feature_leaf(int x86_feature)
87 {
88 return __feature_translate(x86_feature) / 32;
89 }
90
91 /*
92 * Retrieve the bit mask from an X86_FEATURE_* definition. Features contain
93 * the hardware defined bit number (stored in bits 4:0) and a software defined
94 * "word" (stored in bits 31:5). The word is used to index into arrays of
95 * bit masks that hold the per-cpu feature capabilities, e.g. this_cpu_has().
96 */
__feature_bit(int x86_feature)97 static __always_inline u32 __feature_bit(int x86_feature)
98 {
99 x86_feature = __feature_translate(x86_feature);
100
101 reverse_cpuid_check(x86_feature / 32);
102 return 1 << (x86_feature & 31);
103 }
104
105 #define feature_bit(name) __feature_bit(X86_FEATURE_##name)
106
x86_feature_cpuid(unsigned int x86_feature)107 static __always_inline struct cpuid_reg x86_feature_cpuid(unsigned int x86_feature)
108 {
109 unsigned int x86_leaf = __feature_leaf(x86_feature);
110
111 reverse_cpuid_check(x86_leaf);
112 return reverse_cpuid[x86_leaf];
113 }
114
__cpuid_entry_get_reg(struct kvm_cpuid_entry2 * entry,u32 reg)115 static __always_inline u32 *__cpuid_entry_get_reg(struct kvm_cpuid_entry2 *entry,
116 u32 reg)
117 {
118 switch (reg) {
119 case CPUID_EAX:
120 return &entry->eax;
121 case CPUID_EBX:
122 return &entry->ebx;
123 case CPUID_ECX:
124 return &entry->ecx;
125 case CPUID_EDX:
126 return &entry->edx;
127 default:
128 BUILD_BUG();
129 return NULL;
130 }
131 }
132
cpuid_entry_get_reg(struct kvm_cpuid_entry2 * entry,unsigned int x86_feature)133 static __always_inline u32 *cpuid_entry_get_reg(struct kvm_cpuid_entry2 *entry,
134 unsigned int x86_feature)
135 {
136 const struct cpuid_reg cpuid = x86_feature_cpuid(x86_feature);
137
138 return __cpuid_entry_get_reg(entry, cpuid.reg);
139 }
140
cpuid_entry_get(struct kvm_cpuid_entry2 * entry,unsigned int x86_feature)141 static __always_inline u32 cpuid_entry_get(struct kvm_cpuid_entry2 *entry,
142 unsigned int x86_feature)
143 {
144 u32 *reg = cpuid_entry_get_reg(entry, x86_feature);
145
146 return *reg & __feature_bit(x86_feature);
147 }
148
cpuid_entry_has(struct kvm_cpuid_entry2 * entry,unsigned int x86_feature)149 static __always_inline bool cpuid_entry_has(struct kvm_cpuid_entry2 *entry,
150 unsigned int x86_feature)
151 {
152 return cpuid_entry_get(entry, x86_feature);
153 }
154
cpuid_entry_clear(struct kvm_cpuid_entry2 * entry,unsigned int x86_feature)155 static __always_inline void cpuid_entry_clear(struct kvm_cpuid_entry2 *entry,
156 unsigned int x86_feature)
157 {
158 u32 *reg = cpuid_entry_get_reg(entry, x86_feature);
159
160 *reg &= ~__feature_bit(x86_feature);
161 }
162
cpuid_entry_set(struct kvm_cpuid_entry2 * entry,unsigned int x86_feature)163 static __always_inline void cpuid_entry_set(struct kvm_cpuid_entry2 *entry,
164 unsigned int x86_feature)
165 {
166 u32 *reg = cpuid_entry_get_reg(entry, x86_feature);
167
168 *reg |= __feature_bit(x86_feature);
169 }
170
cpuid_entry_change(struct kvm_cpuid_entry2 * entry,unsigned int x86_feature,bool set)171 static __always_inline void cpuid_entry_change(struct kvm_cpuid_entry2 *entry,
172 unsigned int x86_feature,
173 bool set)
174 {
175 u32 *reg = cpuid_entry_get_reg(entry, x86_feature);
176
177 /*
178 * Open coded instead of using cpuid_entry_{clear,set}() to coerce the
179 * compiler into using CMOV instead of Jcc when possible.
180 */
181 if (set)
182 *reg |= __feature_bit(x86_feature);
183 else
184 *reg &= ~__feature_bit(x86_feature);
185 }
186
187 #endif /* ARCH_X86_KVM_REVERSE_CPUID_H */
188