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_2_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
  40 /* Intel-defined sub-features, CPUID level 0x00000007:2 (EDX) */
  41 #define X86_FEATURE_INTEL_PSFD          KVM_X86_FEATURE(CPUID_7_2_EDX, 0)
  42 #define X86_FEATURE_IPRED_CTRL          KVM_X86_FEATURE(CPUID_7_2_EDX, 1)
  43 #define KVM_X86_FEATURE_RRSBA_CTRL      KVM_X86_FEATURE(CPUID_7_2_EDX, 2)
  44 #define X86_FEATURE_DDPD_U              KVM_X86_FEATURE(CPUID_7_2_EDX, 3)
  45 #define KVM_X86_FEATURE_BHI_CTRL        KVM_X86_FEATURE(CPUID_7_2_EDX, 4)
  46 #define X86_FEATURE_MCDT_NO             KVM_X86_FEATURE(CPUID_7_2_EDX, 5)
  47
  48 struct cpuid_reg {
  49         u32 function;
  50         u32 index;
  51         int reg;
  52 };
  53
  54 static const struct cpuid_reg reverse_cpuid[] = {
  55         [CPUID_1_EDX]         = {         1, 0, CPUID_EDX},
  56         [CPUID_8000_0001_EDX] = {0x80000001, 0, CPUID_EDX},
  57         [CPUID_8086_0001_EDX] = {0x80860001, 0, CPUID_EDX},
  58         [CPUID_1_ECX]         = {         1, 0, CPUID_ECX},
  59         [CPUID_C000_0001_EDX] = {0xc0000001, 0, CPUID_EDX},
  60         [CPUID_8000_0001_ECX] = {0x80000001, 0, CPUID_ECX},
  61         [CPUID_7_0_EBX]       = {         7, 0, CPUID_EBX},
  62         [CPUID_D_1_EAX]       = {       0xd, 1, CPUID_EAX},
  63         [CPUID_8000_0008_EBX] = {0x80000008, 0, CPUID_EBX},
  64         [CPUID_6_EAX]         = {         6, 0, CPUID_EAX},
  65         [CPUID_8000_000A_EDX] = {0x8000000a, 0, CPUID_EDX},
  66         [CPUID_7_ECX]         = {         7, 0, CPUID_ECX},
  67         [CPUID_8000_0007_EBX] = {0x80000007, 0, CPUID_EBX},
  68         [CPUID_7_EDX]         = {         7, 0, CPUID_EDX},
  69         [CPUID_7_1_EAX]       = {         7, 1, CPUID_EAX},
  70         [CPUID_12_EAX]        = {0x00000012, 0, CPUID_EAX},
  71         [CPUID_8000_001F_EAX] = {0x8000001f, 0, CPUID_EAX},
  72         [CPUID_8000_0021_EAX] = {0x80000021, 0, CPUID_EAX},
  73         [CPUID_7_2_EDX]       = {         7, 2, CPUID_EDX},
  74 };
  75
  76 /*
  77  * Reverse CPUID and its derivatives can only be used for hardware-defined
  78  * feature words, i.e. words whose bits directly correspond to a CPUID leaf.
  79  * Retrieving a feature bit or masking guest CPUID from a Linux-defined word
  80  * is nonsensical as the bit number/mask is an arbitrary software-defined value
  81  * and can't be used by KVM to query/control guest capabilities.  And obviously
  82  * the leaf being queried must have an entry in the lookup table.
  83  */
  84 static __always_inline void reverse_cpuid_check(unsigned int x86_leaf)
  85 {
  86         BUILD_BUG_ON(NR_CPUID_WORDS != NCAPINTS);
  87         BUILD_BUG_ON(x86_leaf == CPUID_LNX_1);
  88         BUILD_BUG_ON(x86_leaf == CPUID_LNX_2);
  89         BUILD_BUG_ON(x86_leaf == CPUID_LNX_3);
  90         BUILD_BUG_ON(x86_leaf == CPUID_LNX_4);
  91         BUILD_BUG_ON(x86_leaf == CPUID_LNX_5);
  92         BUILD_BUG_ON(x86_leaf >= ARRAY_SIZE(reverse_cpuid));
  93         BUILD_BUG_ON(reverse_cpuid[x86_leaf].function == 0);
  94 }
  95
  96 /*
  97  * Translate feature bits that are scattered in the kernel's cpufeatures word
  98  * into KVM feature words that align with hardware's definitions.
  99  */
 100 static __always_inline u32 __feature_translate(int x86_feature)
 101 {
 102 #define KVM_X86_TRANSLATE_FEATURE(f)    \
 103         case X86_FEATURE_##f: return KVM_X86_FEATURE_##f
 104
 105         switch (x86_feature) {
 106         KVM_X86_TRANSLATE_FEATURE(SGX1);
 107         KVM_X86_TRANSLATE_FEATURE(SGX2);
 108         KVM_X86_TRANSLATE_FEATURE(RRSBA_CTRL);
 109         KVM_X86_TRANSLATE_FEATURE(BHI_CTRL);
 110         default:
 111                 return x86_feature;
 112         }
 113 }
 114
 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  */
 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
 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
 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
 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
 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
 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
 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
 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
 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 */