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Diffstat (limited to 'arch/x86/kvm/reverse_cpuid.h')
| -rw-r--r-- | arch/x86/kvm/reverse_cpuid.h | 187 |
1 files changed, 187 insertions, 0 deletions
diff --git a/arch/x86/kvm/reverse_cpuid.h b/arch/x86/kvm/reverse_cpuid.h new file mode 100644 index 000000000..7eeade35a --- /dev/null +++ b/arch/x86/kvm/reverse_cpuid.h @@ -0,0 +1,187 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef ARCH_X86_KVM_REVERSE_CPUID_H +#define ARCH_X86_KVM_REVERSE_CPUID_H + +#include <uapi/asm/kvm.h> +#include <asm/cpufeature.h> +#include <asm/cpufeatures.h> + +/* + * Hardware-defined CPUID leafs that are scattered in the kernel, but need to + * be directly used by KVM. Note, these word values conflict with the kernel's + * "bug" caps, but KVM doesn't use those. + */ +enum kvm_only_cpuid_leafs { + CPUID_12_EAX = NCAPINTS, + NR_KVM_CPU_CAPS, + + NKVMCAPINTS = NR_KVM_CPU_CAPS - NCAPINTS, +}; + +#define KVM_X86_FEATURE(w, f) ((w)*32 + (f)) + +/* Intel-defined SGX sub-features, CPUID level 0x12 (EAX). */ +#define KVM_X86_FEATURE_SGX1 KVM_X86_FEATURE(CPUID_12_EAX, 0) +#define KVM_X86_FEATURE_SGX2 KVM_X86_FEATURE(CPUID_12_EAX, 1) + +struct cpuid_reg { + u32 function; + u32 index; + int reg; +}; + +static const struct cpuid_reg reverse_cpuid[] = { + [CPUID_1_EDX] = { 1, 0, CPUID_EDX}, + [CPUID_8000_0001_EDX] = {0x80000001, 0, CPUID_EDX}, + [CPUID_8086_0001_EDX] = {0x80860001, 0, CPUID_EDX}, + [CPUID_1_ECX] = { 1, 0, CPUID_ECX}, + [CPUID_C000_0001_EDX] = {0xc0000001, 0, CPUID_EDX}, + [CPUID_8000_0001_ECX] = {0x80000001, 0, CPUID_ECX}, + [CPUID_7_0_EBX] = { 7, 0, CPUID_EBX}, + [CPUID_D_1_EAX] = { 0xd, 1, CPUID_EAX}, + [CPUID_8000_0008_EBX] = {0x80000008, 0, CPUID_EBX}, + [CPUID_6_EAX] = { 6, 0, CPUID_EAX}, + [CPUID_8000_000A_EDX] = {0x8000000a, 0, CPUID_EDX}, + [CPUID_7_ECX] = { 7, 0, CPUID_ECX}, + [CPUID_8000_0007_EBX] = {0x80000007, 0, CPUID_EBX}, + [CPUID_7_EDX] = { 7, 0, CPUID_EDX}, + [CPUID_7_1_EAX] = { 7, 1, CPUID_EAX}, + [CPUID_12_EAX] = {0x00000012, 0, CPUID_EAX}, + [CPUID_8000_001F_EAX] = {0x8000001f, 0, CPUID_EAX}, + [CPUID_8000_0021_EAX] = {0x80000021, 0, CPUID_EAX}, +}; + +/* + * Reverse CPUID and its derivatives can only be used for hardware-defined + * feature words, i.e. words whose bits directly correspond to a CPUID leaf. + * Retrieving a feature bit or masking guest CPUID from a Linux-defined word + * is nonsensical as the bit number/mask is an arbitrary software-defined value + * and can't be used by KVM to query/control guest capabilities. And obviously + * the leaf being queried must have an entry in the lookup table. + */ +static __always_inline void reverse_cpuid_check(unsigned int x86_leaf) +{ + BUILD_BUG_ON(x86_leaf == CPUID_LNX_1); + BUILD_BUG_ON(x86_leaf == CPUID_LNX_2); + BUILD_BUG_ON(x86_leaf == CPUID_LNX_3); + BUILD_BUG_ON(x86_leaf == CPUID_LNX_4); + BUILD_BUG_ON(x86_leaf >= ARRAY_SIZE(reverse_cpuid)); + BUILD_BUG_ON(reverse_cpuid[x86_leaf].function == 0); +} + +/* + * Translate feature bits that are scattered in the kernel's cpufeatures word + * into KVM feature words that align with hardware's definitions. + */ +static __always_inline u32 __feature_translate(int x86_feature) +{ + if (x86_feature == X86_FEATURE_SGX1) + return KVM_X86_FEATURE_SGX1; + else if (x86_feature == X86_FEATURE_SGX2) + return KVM_X86_FEATURE_SGX2; + + return x86_feature; +} + +static __always_inline u32 __feature_leaf(int x86_feature) +{ + return __feature_translate(x86_feature) / 32; +} + +/* + * Retrieve the bit mask from an X86_FEATURE_* definition. Features contain + * the hardware defined bit number (stored in bits 4:0) and a software defined + * "word" (stored in bits 31:5). The word is used to index into arrays of + * bit masks that hold the per-cpu feature capabilities, e.g. this_cpu_has(). + */ +static __always_inline u32 __feature_bit(int x86_feature) +{ + x86_feature = __feature_translate(x86_feature); + + reverse_cpuid_check(x86_feature / 32); + return 1 << (x86_feature & 31); +} + +#define feature_bit(name) __feature_bit(X86_FEATURE_##name) + +static __always_inline struct cpuid_reg x86_feature_cpuid(unsigned int x86_feature) +{ + unsigned int x86_leaf = __feature_leaf(x86_feature); + + reverse_cpuid_check(x86_leaf); + return reverse_cpuid[x86_leaf]; +} + +static __always_inline u32 *__cpuid_entry_get_reg(struct kvm_cpuid_entry2 *entry, + u32 reg) +{ + switch (reg) { + case CPUID_EAX: + return &entry->eax; + case CPUID_EBX: + return &entry->ebx; + case CPUID_ECX: + return &entry->ecx; + case CPUID_EDX: + return &entry->edx; + default: + BUILD_BUG(); + return NULL; + } +} + +static __always_inline u32 *cpuid_entry_get_reg(struct kvm_cpuid_entry2 *entry, + unsigned int x86_feature) +{ + const struct cpuid_reg cpuid = x86_feature_cpuid(x86_feature); + + return __cpuid_entry_get_reg(entry, cpuid.reg); +} + +static __always_inline u32 cpuid_entry_get(struct kvm_cpuid_entry2 *entry, + unsigned int x86_feature) +{ + u32 *reg = cpuid_entry_get_reg(entry, x86_feature); + + return *reg & __feature_bit(x86_feature); +} + +static __always_inline bool cpuid_entry_has(struct kvm_cpuid_entry2 *entry, + unsigned int x86_feature) +{ + return cpuid_entry_get(entry, x86_feature); +} + +static __always_inline void cpuid_entry_clear(struct kvm_cpuid_entry2 *entry, + unsigned int x86_feature) +{ + u32 *reg = cpuid_entry_get_reg(entry, x86_feature); + + *reg &= ~__feature_bit(x86_feature); +} + +static __always_inline void cpuid_entry_set(struct kvm_cpuid_entry2 *entry, + unsigned int x86_feature) +{ + u32 *reg = cpuid_entry_get_reg(entry, x86_feature); + + *reg |= __feature_bit(x86_feature); +} + +static __always_inline void cpuid_entry_change(struct kvm_cpuid_entry2 *entry, + unsigned int x86_feature, + bool set) +{ + u32 *reg = cpuid_entry_get_reg(entry, x86_feature); + + /* + * Open coded instead of using cpuid_entry_{clear,set}() to coerce the + * compiler into using CMOV instead of Jcc when possible. + */ + if (set) + *reg |= __feature_bit(x86_feature); + else + *reg &= ~__feature_bit(x86_feature); +} + +#endif /* ARCH_X86_KVM_REVERSE_CPUID_H */ |