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