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 either scattered by the kernel or are
11 * unknown to the kernel, but need to be directly used by KVM. Note, these
12 * word values conflict with the kernel's "bug" caps, but KVM doesn't use those.
13 */
14 enum kvm_only_cpuid_leafs {
15 CPUID_12_EAX = NCAPINTS,
16 CPUID_7_1_EDX,
17 CPUID_8000_0007_EDX,
18 NR_KVM_CPU_CAPS,
19
20 NKVMCAPINTS = NR_KVM_CPU_CAPS - NCAPINTS,
21 };
22
23 /*
24 * Define a KVM-only feature flag.
25 *
26 * For features that are scattered by cpufeatures.h, __feature_translate() also
27 * needs to be updated to translate the kernel-defined feature into the
28 * KVM-defined feature.
29 *
30 * For features that are 100% KVM-only, i.e. not defined by cpufeatures.h,
31 * forego the intermediate KVM_X86_FEATURE and directly define X86_FEATURE_* so
32 * that X86_FEATURE_* can be used in KVM. No __feature_translate() handling is
33 * needed in this case.
34 */
35 #define KVM_X86_FEATURE(w, f) ((w)*32 + (f))
36
37 /* Intel-defined SGX sub-features, CPUID level 0x12 (EAX). */
38 #define KVM_X86_FEATURE_SGX1 KVM_X86_FEATURE(CPUID_12_EAX, 0)
39 #define KVM_X86_FEATURE_SGX2 KVM_X86_FEATURE(CPUID_12_EAX, 1)
40 #define KVM_X86_FEATURE_SGX_EDECCSSA KVM_X86_FEATURE(CPUID_12_EAX, 11)
41
42 /* Intel-defined sub-features, CPUID level 0x00000007:1 (EDX) */
43 #define X86_FEATURE_AVX_VNNI_INT8 KVM_X86_FEATURE(CPUID_7_1_EDX, 4)
44 #define X86_FEATURE_AVX_NE_CONVERT KVM_X86_FEATURE(CPUID_7_1_EDX, 5)
45 #define X86_FEATURE_PREFETCHITI KVM_X86_FEATURE(CPUID_7_1_EDX, 14)
46
47 /* CPUID level 0x80000007 (EDX). */
48 #define KVM_X86_FEATURE_CONSTANT_TSC KVM_X86_FEATURE(CPUID_8000_0007_EDX, 8)
49
50 struct cpuid_reg {
51 u32 function;
52 u32 index;
53 int reg;
54 };
55
56 static const struct cpuid_reg reverse_cpuid[] = {
57 [CPUID_1_EDX] = { 1, 0, CPUID_EDX},
58 [CPUID_8000_0001_EDX] = {0x80000001, 0, CPUID_EDX},
59 [CPUID_8086_0001_EDX] = {0x80860001, 0, CPUID_EDX},
60 [CPUID_1_ECX] = { 1, 0, CPUID_ECX},
61 [CPUID_C000_0001_EDX] = {0xc0000001, 0, CPUID_EDX},
62 [CPUID_8000_0001_ECX] = {0x80000001, 0, CPUID_ECX},
63 [CPUID_7_0_EBX] = { 7, 0, CPUID_EBX},
64 [CPUID_D_1_EAX] = { 0xd, 1, CPUID_EAX},
65 [CPUID_8000_0008_EBX] = {0x80000008, 0, CPUID_EBX},
66 [CPUID_6_EAX] = { 6, 0, CPUID_EAX},
67 [CPUID_8000_000A_EDX] = {0x8000000a, 0, CPUID_EDX},
68 [CPUID_7_ECX] = { 7, 0, CPUID_ECX},
69 [CPUID_8000_0007_EBX] = {0x80000007, 0, CPUID_EBX},
70 [CPUID_7_EDX] = { 7, 0, CPUID_EDX},
71 [CPUID_7_1_EAX] = { 7, 1, CPUID_EAX},
72 [CPUID_12_EAX] = {0x00000012, 0, CPUID_EAX},
73 [CPUID_8000_001F_EAX] = {0x8000001f, 0, CPUID_EAX},
74 [CPUID_7_1_EDX] = { 7, 1, CPUID_EDX},
75 [CPUID_8000_0007_EDX] = {0x80000007, 0, CPUID_EDX},
76 [CPUID_8000_0021_EAX] = {0x80000021, 0, CPUID_EAX},
77 };
78
79 /*
80 * Reverse CPUID and its derivatives can only be used for hardware-defined
81 * feature words, i.e. words whose bits directly correspond to a CPUID leaf.
82 * Retrieving a feature bit or masking guest CPUID from a Linux-defined word
83 * is nonsensical as the bit number/mask is an arbitrary software-defined value
84 * and can't be used by KVM to query/control guest capabilities. And obviously
85 * the leaf being queried must have an entry in the lookup table.
86 */
reverse_cpuid_check(unsigned int x86_leaf)87 static __always_inline void reverse_cpuid_check(unsigned int x86_leaf)
88 {
89 BUILD_BUG_ON(x86_leaf == CPUID_LNX_1);
90 BUILD_BUG_ON(x86_leaf == CPUID_LNX_2);
91 BUILD_BUG_ON(x86_leaf == CPUID_LNX_3);
92 BUILD_BUG_ON(x86_leaf == CPUID_LNX_4);
93 BUILD_BUG_ON(x86_leaf >= ARRAY_SIZE(reverse_cpuid));
94 BUILD_BUG_ON(reverse_cpuid[x86_leaf].function == 0);
95 }
96
97 /*
98 * Translate feature bits that are scattered in the kernel's cpufeatures word
99 * into KVM feature words that align with hardware's definitions.
100 */
__feature_translate(int x86_feature)101 static __always_inline u32 __feature_translate(int x86_feature)
102 {
103 if (x86_feature == X86_FEATURE_SGX1)
104 return KVM_X86_FEATURE_SGX1;
105 else if (x86_feature == X86_FEATURE_SGX2)
106 return KVM_X86_FEATURE_SGX2;
107 else if (x86_feature == X86_FEATURE_SGX_EDECCSSA)
108 return KVM_X86_FEATURE_SGX_EDECCSSA;
109 else if (x86_feature == X86_FEATURE_CONSTANT_TSC)
110 return KVM_X86_FEATURE_CONSTANT_TSC;
111
112 return x86_feature;
113 }
114
__feature_leaf(int x86_feature)115 static __always_inline u32 __feature_leaf(int x86_feature)
116 {
117 return __feature_translate(x86_feature) / 32;
118 }
119
120 /*
121 * Retrieve the bit mask from an X86_FEATURE_* definition. Features contain
122 * the hardware defined bit number (stored in bits 4:0) and a software defined
123 * "word" (stored in bits 31:5). The word is used to index into arrays of
124 * bit masks that hold the per-cpu feature capabilities, e.g. this_cpu_has().
125 */
__feature_bit(int x86_feature)126 static __always_inline u32 __feature_bit(int x86_feature)
127 {
128 x86_feature = __feature_translate(x86_feature);
129
130 reverse_cpuid_check(x86_feature / 32);
131 return 1 << (x86_feature & 31);
132 }
133
134 #define feature_bit(name) __feature_bit(X86_FEATURE_##name)
135
x86_feature_cpuid(unsigned int x86_feature)136 static __always_inline struct cpuid_reg x86_feature_cpuid(unsigned int x86_feature)
137 {
138 unsigned int x86_leaf = __feature_leaf(x86_feature);
139
140 reverse_cpuid_check(x86_leaf);
141 return reverse_cpuid[x86_leaf];
142 }
143
__cpuid_entry_get_reg(struct kvm_cpuid_entry2 * entry,u32 reg)144 static __always_inline u32 *__cpuid_entry_get_reg(struct kvm_cpuid_entry2 *entry,
145 u32 reg)
146 {
147 switch (reg) {
148 case CPUID_EAX:
149 return &entry->eax;
150 case CPUID_EBX:
151 return &entry->ebx;
152 case CPUID_ECX:
153 return &entry->ecx;
154 case CPUID_EDX:
155 return &entry->edx;
156 default:
157 BUILD_BUG();
158 return NULL;
159 }
160 }
161
cpuid_entry_get_reg(struct kvm_cpuid_entry2 * entry,unsigned int x86_feature)162 static __always_inline u32 *cpuid_entry_get_reg(struct kvm_cpuid_entry2 *entry,
163 unsigned int x86_feature)
164 {
165 const struct cpuid_reg cpuid = x86_feature_cpuid(x86_feature);
166
167 return __cpuid_entry_get_reg(entry, cpuid.reg);
168 }
169
cpuid_entry_get(struct kvm_cpuid_entry2 * entry,unsigned int x86_feature)170 static __always_inline u32 cpuid_entry_get(struct kvm_cpuid_entry2 *entry,
171 unsigned int x86_feature)
172 {
173 u32 *reg = cpuid_entry_get_reg(entry, x86_feature);
174
175 return *reg & __feature_bit(x86_feature);
176 }
177
cpuid_entry_has(struct kvm_cpuid_entry2 * entry,unsigned int x86_feature)178 static __always_inline bool cpuid_entry_has(struct kvm_cpuid_entry2 *entry,
179 unsigned int x86_feature)
180 {
181 return cpuid_entry_get(entry, x86_feature);
182 }
183
cpuid_entry_clear(struct kvm_cpuid_entry2 * entry,unsigned int x86_feature)184 static __always_inline void cpuid_entry_clear(struct kvm_cpuid_entry2 *entry,
185 unsigned int x86_feature)
186 {
187 u32 *reg = cpuid_entry_get_reg(entry, x86_feature);
188
189 *reg &= ~__feature_bit(x86_feature);
190 }
191
cpuid_entry_set(struct kvm_cpuid_entry2 * entry,unsigned int x86_feature)192 static __always_inline void cpuid_entry_set(struct kvm_cpuid_entry2 *entry,
193 unsigned int x86_feature)
194 {
195 u32 *reg = cpuid_entry_get_reg(entry, x86_feature);
196
197 *reg |= __feature_bit(x86_feature);
198 }
199
cpuid_entry_change(struct kvm_cpuid_entry2 * entry,unsigned int x86_feature,bool set)200 static __always_inline void cpuid_entry_change(struct kvm_cpuid_entry2 *entry,
201 unsigned int x86_feature,
202 bool set)
203 {
204 u32 *reg = cpuid_entry_get_reg(entry, x86_feature);
205
206 /*
207 * Open coded instead of using cpuid_entry_{clear,set}() to coerce the
208 * compiler into using CMOV instead of Jcc when possible.
209 */
210 if (set)
211 *reg |= __feature_bit(x86_feature);
212 else
213 *reg &= ~__feature_bit(x86_feature);
214 }
215
216 #endif /* ARCH_X86_KVM_REVERSE_CPUID_H */
217