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         [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  */
  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  */
  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
  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  */
  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
 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
 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
 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
 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
 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
 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
 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
 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 */