x86/kvm/reverse_cpuid.h

0001 /* SPDX-License-Identifier: GPL-2.0 */
0002 #ifndef ARCH_X86_KVM_REVERSE_CPUID_H
0003 #define ARCH_X86_KVM_REVERSE_CPUID_H
0004
0005 #include <uapi/asm/kvm.h>
0006 #include <asm/cpufeature.h>
0007 #include <asm/cpufeatures.h>
0008
0009 /*
0010  * Hardware-defined CPUID leafs that are scattered in the kernel, but need to
0011  * be directly used by KVM.  Note, these word values conflict with the kernel's
0012  * "bug" caps, but KVM doesn't use those.
0013  */
0014 enum kvm_only_cpuid_leafs {
0015     CPUID_12_EAX     = NCAPINTS,
0016     NR_KVM_CPU_CAPS,
0017
0018     NKVMCAPINTS = NR_KVM_CPU_CAPS - NCAPINTS,
0019 };
0020
0021 #define KVM_X86_FEATURE(w, f)       ((w)*32 + (f))
0022
0023 /* Intel-defined SGX sub-features, CPUID level 0x12 (EAX). */
0024 #define KVM_X86_FEATURE_SGX1        KVM_X86_FEATURE(CPUID_12_EAX, 0)
0025 #define KVM_X86_FEATURE_SGX2        KVM_X86_FEATURE(CPUID_12_EAX, 1)
0026
0027 struct cpuid_reg {
0028     u32 function;
0029     u32 index;
0030     int reg;
0031 };
0032
0033 static const struct cpuid_reg reverse_cpuid[] = {
0034     [CPUID_1_EDX]         = {         1, 0, CPUID_EDX},
0035     [CPUID_8000_0001_EDX] = {0x80000001, 0, CPUID_EDX},
0036     [CPUID_8086_0001_EDX] = {0x80860001, 0, CPUID_EDX},
0037     [CPUID_1_ECX]         = {         1, 0, CPUID_ECX},
0038     [CPUID_C000_0001_EDX] = {0xc0000001, 0, CPUID_EDX},
0039     [CPUID_8000_0001_ECX] = {0x80000001, 0, CPUID_ECX},
0040     [CPUID_7_0_EBX]       = {         7, 0, CPUID_EBX},
0041     [CPUID_D_1_EAX]       = {       0xd, 1, CPUID_EAX},
0042     [CPUID_8000_0008_EBX] = {0x80000008, 0, CPUID_EBX},
0043     [CPUID_6_EAX]         = {         6, 0, CPUID_EAX},
0044     [CPUID_8000_000A_EDX] = {0x8000000a, 0, CPUID_EDX},
0045     [CPUID_7_ECX]         = {         7, 0, CPUID_ECX},
0046     [CPUID_8000_0007_EBX] = {0x80000007, 0, CPUID_EBX},
0047     [CPUID_7_EDX]         = {         7, 0, CPUID_EDX},
0048     [CPUID_7_1_EAX]       = {         7, 1, CPUID_EAX},
0049     [CPUID_12_EAX]        = {0x00000012, 0, CPUID_EAX},
0050     [CPUID_8000_001F_EAX] = {0x8000001f, 0, CPUID_EAX},
0051 };
0052
0053 /*
0054  * Reverse CPUID and its derivatives can only be used for hardware-defined
0055  * feature words, i.e. words whose bits directly correspond to a CPUID leaf.
0056  * Retrieving a feature bit or masking guest CPUID from a Linux-defined word
0057  * is nonsensical as the bit number/mask is an arbitrary software-defined value
0058  * and can't be used by KVM to query/control guest capabilities.  And obviously
0059  * the leaf being queried must have an entry in the lookup table.
0060  */
0061 static __always_inline void reverse_cpuid_check(unsigned int x86_leaf)
0062 {
0063     BUILD_BUG_ON(x86_leaf == CPUID_LNX_1);
0064     BUILD_BUG_ON(x86_leaf == CPUID_LNX_2);
0065     BUILD_BUG_ON(x86_leaf == CPUID_LNX_3);
0066     BUILD_BUG_ON(x86_leaf == CPUID_LNX_4);
0067     BUILD_BUG_ON(x86_leaf >= ARRAY_SIZE(reverse_cpuid));
0068     BUILD_BUG_ON(reverse_cpuid[x86_leaf].function == 0);
0069 }
0070
0071 /*
0072  * Translate feature bits that are scattered in the kernel's cpufeatures word
0073  * into KVM feature words that align with hardware's definitions.
0074  */
0075 static __always_inline u32 __feature_translate(int x86_feature)
0076 {
0077     if (x86_feature == X86_FEATURE_SGX1)
0078         return KVM_X86_FEATURE_SGX1;
0079     else if (x86_feature == X86_FEATURE_SGX2)
0080         return KVM_X86_FEATURE_SGX2;
0081
0082     return x86_feature;
0083 }
0084
0085 static __always_inline u32 __feature_leaf(int x86_feature)
0086 {
0087     return __feature_translate(x86_feature) / 32;
0088 }
0089
0090 /*
0091  * Retrieve the bit mask from an X86_FEATURE_* definition.  Features contain
0092  * the hardware defined bit number (stored in bits 4:0) and a software defined
0093  * "word" (stored in bits 31:5).  The word is used to index into arrays of
0094  * bit masks that hold the per-cpu feature capabilities, e.g. this_cpu_has().
0095  */
0096 static __always_inline u32 __feature_bit(int x86_feature)
0097 {
0098     x86_feature = __feature_translate(x86_feature);
0099
0100     reverse_cpuid_check(x86_feature / 32);
0101     return 1 << (x86_feature & 31);
0102 }
0103
0104 #define feature_bit(name)  __feature_bit(X86_FEATURE_##name)
0105
0106 static __always_inline struct cpuid_reg x86_feature_cpuid(unsigned int x86_feature)
0107 {
0108     unsigned int x86_leaf = __feature_leaf(x86_feature);
0109
0110     reverse_cpuid_check(x86_leaf);
0111     return reverse_cpuid[x86_leaf];
0112 }
0113
0114 static __always_inline u32 *__cpuid_entry_get_reg(struct kvm_cpuid_entry2 *entry,
0115                           u32 reg)
0116 {
0117     switch (reg) {
0118     case CPUID_EAX:
0119         return &entry->eax;
0120     case CPUID_EBX:
0121         return &entry->ebx;
0122     case CPUID_ECX:
0123         return &entry->ecx;
0124     case CPUID_EDX:
0125         return &entry->edx;
0126     default:
0127         BUILD_BUG();
0128         return NULL;
0129     }
0130 }
0131
0132 static __always_inline u32 *cpuid_entry_get_reg(struct kvm_cpuid_entry2 *entry,
0133                         unsigned int x86_feature)
0134 {
0135     const struct cpuid_reg cpuid = x86_feature_cpuid(x86_feature);
0136
0137     return __cpuid_entry_get_reg(entry, cpuid.reg);
0138 }
0139
0140 static __always_inline u32 cpuid_entry_get(struct kvm_cpuid_entry2 *entry,
0141                        unsigned int x86_feature)
0142 {
0143     u32 *reg = cpuid_entry_get_reg(entry, x86_feature);
0144
0145     return *reg & __feature_bit(x86_feature);
0146 }
0147
0148 static __always_inline bool cpuid_entry_has(struct kvm_cpuid_entry2 *entry,
0149                         unsigned int x86_feature)
0150 {
0151     return cpuid_entry_get(entry, x86_feature);
0152 }
0153
0154 static __always_inline void cpuid_entry_clear(struct kvm_cpuid_entry2 *entry,
0155                           unsigned int x86_feature)
0156 {
0157     u32 *reg = cpuid_entry_get_reg(entry, x86_feature);
0158
0159     *reg &= ~__feature_bit(x86_feature);
0160 }
0161
0162 static __always_inline void cpuid_entry_set(struct kvm_cpuid_entry2 *entry,
0163                         unsigned int x86_feature)
0164 {
0165     u32 *reg = cpuid_entry_get_reg(entry, x86_feature);
0166
0167     *reg |= __feature_bit(x86_feature);
0168 }
0169
0170 static __always_inline void cpuid_entry_change(struct kvm_cpuid_entry2 *entry,
0171                            unsigned int x86_feature,
0172                            bool set)
0173 {
0174     u32 *reg = cpuid_entry_get_reg(entry, x86_feature);
0175
0176     /*
0177      * Open coded instead of using cpuid_entry_{clear,set}() to coerce the
0178      * compiler into using CMOV instead of Jcc when possible.
0179      */
0180     if (set)
0181         *reg |= __feature_bit(x86_feature);
0182     else
0183         *reg &= ~__feature_bit(x86_feature);
0184 }
0185
0186 #endif /* ARCH_X86_KVM_REVERSE_CPUID_H */