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 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         CPUID_8000_0022_EAX,
  19         NR_KVM_CPU_CAPS,
  20
  21         NKVMCAPINTS = NR_KVM_CPU_CAPS - NCAPINTS,
  22 };
  23
  24 /*
  25  * Define a KVM-only feature flag.
  26  *
  27  * For features that are scattered by cpufeatures.h, __feature_translate() also
  28  * needs to be updated to translate the kernel-defined feature into the
  29  * KVM-defined feature.
  30  *
  31  * For features that are 100% KVM-only, i.e. not defined by cpufeatures.h,
  32  * forego the intermediate KVM_X86_FEATURE and directly define X86_FEATURE_* so
  33  * that X86_FEATURE_* can be used in KVM.  No __feature_translate() handling is
  34  * needed in this case.
  35  */
  36 #define KVM_X86_FEATURE(w, f)           ((w)*32 + (f))
  37
  38 /* Intel-defined SGX sub-features, CPUID level 0x12 (EAX). */
  39 #define KVM_X86_FEATURE_SGX1            KVM_X86_FEATURE(CPUID_12_EAX, 0)
  40 #define KVM_X86_FEATURE_SGX2            KVM_X86_FEATURE(CPUID_12_EAX, 1)
  41 #define KVM_X86_FEATURE_SGX_EDECCSSA    KVM_X86_FEATURE(CPUID_12_EAX, 11)
  42
  43 /* Intel-defined sub-features, CPUID level 0x00000007:1 (EDX) */
  44 #define X86_FEATURE_AVX_VNNI_INT8       KVM_X86_FEATURE(CPUID_7_1_EDX, 4)
  45 #define X86_FEATURE_AVX_NE_CONVERT      KVM_X86_FEATURE(CPUID_7_1_EDX, 5)
  46 #define X86_FEATURE_PREFETCHITI         KVM_X86_FEATURE(CPUID_7_1_EDX, 14)
  47
  48 /* CPUID level 0x80000007 (EDX). */
  49 #define KVM_X86_FEATURE_CONSTANT_TSC    KVM_X86_FEATURE(CPUID_8000_0007_EDX, 8)
  50
  51 /* CPUID level 0x80000022 (EAX) */
  52 #define KVM_X86_FEATURE_PERFMON_V2      KVM_X86_FEATURE(CPUID_8000_0022_EAX, 0)
  53
  54 struct cpuid_reg {
  55         u32 function;
  56         u32 index;
  57         int reg;
  58 };
  59
  60 static const struct cpuid_reg reverse_cpuid[] = {
  61         [CPUID_1_EDX]         = {         1, 0, CPUID_EDX},
  62         [CPUID_8000_0001_EDX] = {0x80000001, 0, CPUID_EDX},
  63         [CPUID_8086_0001_EDX] = {0x80860001, 0, CPUID_EDX},
  64         [CPUID_1_ECX]         = {         1, 0, CPUID_ECX},
  65         [CPUID_C000_0001_EDX] = {0xc0000001, 0, CPUID_EDX},
  66         [CPUID_8000_0001_ECX] = {0x80000001, 0, CPUID_ECX},
  67         [CPUID_7_0_EBX]       = {         7, 0, CPUID_EBX},
  68         [CPUID_D_1_EAX]       = {       0xd, 1, CPUID_EAX},
  69         [CPUID_8000_0008_EBX] = {0x80000008, 0, CPUID_EBX},
  70         [CPUID_6_EAX]         = {         6, 0, CPUID_EAX},
  71         [CPUID_8000_000A_EDX] = {0x8000000a, 0, CPUID_EDX},
  72         [CPUID_7_ECX]         = {         7, 0, CPUID_ECX},
  73         [CPUID_8000_0007_EBX] = {0x80000007, 0, CPUID_EBX},
  74         [CPUID_7_EDX]         = {         7, 0, CPUID_EDX},
  75         [CPUID_7_1_EAX]       = {         7, 1, CPUID_EAX},
  76         [CPUID_12_EAX]        = {0x00000012, 0, CPUID_EAX},
  77         [CPUID_8000_001F_EAX] = {0x8000001f, 0, CPUID_EAX},
  78         [CPUID_7_1_EDX]       = {         7, 1, CPUID_EDX},
  79         [CPUID_8000_0007_EDX] = {0x80000007, 0, CPUID_EDX},
  80         [CPUID_8000_0021_EAX] = {0x80000021, 0, CPUID_EAX},
  81         [CPUID_8000_0022_EAX] = {0x80000022, 0, CPUID_EAX},
  82 };
  83
  84 /*
  85  * Reverse CPUID and its derivatives can only be used for hardware-defined
  86  * feature words, i.e. words whose bits directly correspond to a CPUID leaf.
  87  * Retrieving a feature bit or masking guest CPUID from a Linux-defined word
  88  * is nonsensical as the bit number/mask is an arbitrary software-defined value
  89  * and can't be used by KVM to query/control guest capabilities.  And obviously
  90  * the leaf being queried must have an entry in the lookup table.
  91  */
  92 static __always_inline void reverse_cpuid_check(unsigned int x86_leaf)
  93 {
  94         BUILD_BUG_ON(x86_leaf == CPUID_LNX_1);
  95         BUILD_BUG_ON(x86_leaf == CPUID_LNX_2);
  96         BUILD_BUG_ON(x86_leaf == CPUID_LNX_3);
  97         BUILD_BUG_ON(x86_leaf == CPUID_LNX_4);
  98         BUILD_BUG_ON(x86_leaf >= ARRAY_SIZE(reverse_cpuid));
  99         BUILD_BUG_ON(reverse_cpuid[x86_leaf].function == 0);
 100 }
 101
 102 /*
 103  * Translate feature bits that are scattered in the kernel's cpufeatures word
 104  * into KVM feature words that align with hardware's definitions.
 105  */
 106 static __always_inline u32 __feature_translate(int x86_feature)
 107 {
 108         if (x86_feature == X86_FEATURE_SGX1)
 109                 return KVM_X86_FEATURE_SGX1;
 110         else if (x86_feature == X86_FEATURE_SGX2)
 111                 return KVM_X86_FEATURE_SGX2;
 112         else if (x86_feature == X86_FEATURE_SGX_EDECCSSA)
 113                 return KVM_X86_FEATURE_SGX_EDECCSSA;
 114         else if (x86_feature == X86_FEATURE_CONSTANT_TSC)
 115                 return KVM_X86_FEATURE_CONSTANT_TSC;
 116         else if (x86_feature == X86_FEATURE_PERFMON_V2)
 117                 return KVM_X86_FEATURE_PERFMON_V2;
 118
 119         return x86_feature;
 120 }
 121
 122 static __always_inline u32 __feature_leaf(int x86_feature)
 123 {
 124         return __feature_translate(x86_feature) / 32;
 125 }
 126
 127 /*
 128  * Retrieve the bit mask from an X86_FEATURE_* definition.  Features contain
 129  * the hardware defined bit number (stored in bits 4:0) and a software defined
 130  * "word" (stored in bits 31:5).  The word is used to index into arrays of
 131  * bit masks that hold the per-cpu feature capabilities, e.g. this_cpu_has().
 132  */
 133 static __always_inline u32 __feature_bit(int x86_feature)
 134 {
 135         x86_feature = __feature_translate(x86_feature);
 136
 137         reverse_cpuid_check(x86_feature / 32);
 138         return 1 << (x86_feature & 31);
 139 }
 140
 141 #define feature_bit(name)  __feature_bit(X86_FEATURE_##name)
 142
 143 static __always_inline struct cpuid_reg x86_feature_cpuid(unsigned int x86_feature)
 144 {
 145         unsigned int x86_leaf = __feature_leaf(x86_feature);
 146
 147         reverse_cpuid_check(x86_leaf);
 148         return reverse_cpuid[x86_leaf];
 149 }
 150
 151 static __always_inline u32 *__cpuid_entry_get_reg(struct kvm_cpuid_entry2 *entry,
 152                                                   u32 reg)
 153 {
 154         switch (reg) {
 155         case CPUID_EAX:
 156                 return &entry->eax;
 157         case CPUID_EBX:
 158                 return &entry->ebx;
 159         case CPUID_ECX:
 160                 return &entry->ecx;
 161         case CPUID_EDX:
 162                 return &entry->edx;
 163         default:
 164                 BUILD_BUG();
 165                 return NULL;
 166         }
 167 }
 168
 169 static __always_inline u32 *cpuid_entry_get_reg(struct kvm_cpuid_entry2 *entry,
 170                                                 unsigned int x86_feature)
 171 {
 172         const struct cpuid_reg cpuid = x86_feature_cpuid(x86_feature);
 173
 174         return __cpuid_entry_get_reg(entry, cpuid.reg);
 175 }
 176
 177 static __always_inline u32 cpuid_entry_get(struct kvm_cpuid_entry2 *entry,
 178                                            unsigned int x86_feature)
 179 {
 180         u32 *reg = cpuid_entry_get_reg(entry, x86_feature);
 181
 182         return *reg & __feature_bit(x86_feature);
 183 }
 184
 185 static __always_inline bool cpuid_entry_has(struct kvm_cpuid_entry2 *entry,
 186                                             unsigned int x86_feature)
 187 {
 188         return cpuid_entry_get(entry, x86_feature);
 189 }
 190
 191 static __always_inline void cpuid_entry_clear(struct kvm_cpuid_entry2 *entry,
 192                                               unsigned int x86_feature)
 193 {
 194         u32 *reg = cpuid_entry_get_reg(entry, x86_feature);
 195
 196         *reg &= ~__feature_bit(x86_feature);
 197 }
 198
 199 static __always_inline void cpuid_entry_set(struct kvm_cpuid_entry2 *entry,
 200                                             unsigned int x86_feature)
 201 {
 202         u32 *reg = cpuid_entry_get_reg(entry, x86_feature);
 203
 204         *reg |= __feature_bit(x86_feature);
 205 }
 206
 207 static __always_inline void cpuid_entry_change(struct kvm_cpuid_entry2 *entry,
 208                                                unsigned int x86_feature,
 209                                                bool set)
 210 {
 211         u32 *reg = cpuid_entry_get_reg(entry, x86_feature);
 212
 213         /*
 214          * Open coded instead of using cpuid_entry_{clear,set}() to coerce the
 215          * compiler into using CMOV instead of Jcc when possible.
 216          */
 217         if (set)
 218                 *reg |= __feature_bit(x86_feature);
 219         else
 220                 *reg &= ~__feature_bit(x86_feature);
 221 }
 222
 223 #endif /* ARCH_X86_KVM_REVERSE_CPUID_H */