arch/x86/kvm/reverse_cpuid.h

   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  */
  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  */
  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
  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  */
  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
 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
 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
 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
 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
 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
 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
 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
 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 */