reverse_cpuid.h

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/* 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 either scattered by the kernel or are
 * unknown to 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,
    CPUID_7_1_EDX,
    CPUID_8000_0007_EDX,
    CPUID_8000_0022_EAX,
    CPUID_7_2_EDX,
    NR_KVM_CPU_CAPS,
 
    NKVMCAPINTS = NR_KVM_CPU_CAPS - NCAPINTS,
};
 
/*
 * Define a KVM-only feature flag.
 *
 * For features that are scattered by cpufeatures.h, __feature_translate() also
 * needs to be updated to translate the kernel-defined feature into the
 * KVM-defined feature.
 *
 * For features that are 100% KVM-only, i.e. not defined by cpufeatures.h,
 * forego the intermediate KVM_X86_FEATURE and directly define X86_FEATURE_* so
 * that X86_FEATURE_* can be used in KVM.  No __feature_translate() handling is
 * needed in this case.
 */
#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)
#define KVM_X86_FEATURE_SGX_EDECCSSA    KVM_X86_FEATURE(CPUID_12_EAX, 11)
 
/* Intel-defined sub-features, CPUID level 0x00000007:1 (EDX) */
#define X86_FEATURE_AVX_VNNI_INT8       KVM_X86_FEATURE(CPUID_7_1_EDX, 4)
#define X86_FEATURE_AVX_NE_CONVERT      KVM_X86_FEATURE(CPUID_7_1_EDX, 5)
#define X86_FEATURE_AMX_COMPLEX         KVM_X86_FEATURE(CPUID_7_1_EDX, 8)
#define X86_FEATURE_PREFETCHITI         KVM_X86_FEATURE(CPUID_7_1_EDX, 14)
 
/* Intel-defined sub-features, CPUID level 0x00000007:2 (EDX) */
#define X86_FEATURE_INTEL_PSFD      KVM_X86_FEATURE(CPUID_7_2_EDX, 0)
#define X86_FEATURE_IPRED_CTRL      KVM_X86_FEATURE(CPUID_7_2_EDX, 1)
#define KVM_X86_FEATURE_RRSBA_CTRL  KVM_X86_FEATURE(CPUID_7_2_EDX, 2)
#define X86_FEATURE_DDPD_U      KVM_X86_FEATURE(CPUID_7_2_EDX, 3)
#define KVM_X86_FEATURE_BHI_CTRL    KVM_X86_FEATURE(CPUID_7_2_EDX, 4)
#define X86_FEATURE_MCDT_NO     KVM_X86_FEATURE(CPUID_7_2_EDX, 5)
 
/* CPUID level 0x80000007 (EDX). */
#define KVM_X86_FEATURE_CONSTANT_TSC    KVM_X86_FEATURE(CPUID_8000_0007_EDX, 8)
 
/* CPUID level 0x80000022 (EAX) */
#define KVM_X86_FEATURE_PERFMON_V2  KVM_X86_FEATURE(CPUID_8000_0022_EAX, 0)
 
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_7_1_EDX]       = {         7, 1, CPUID_EDX},
    [CPUID_8000_0007_EDX] = {0x80000007, 0, CPUID_EDX},
    [CPUID_8000_0021_EAX] = {0x80000021, 0, CPUID_EAX},
    [CPUID_8000_0022_EAX] = {0x80000022, 0, CPUID_EAX},
    [CPUID_7_2_EDX]       = {         7, 2, CPUID_EDX},
};
 
/*
 * 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(NR_CPUID_WORDS != NCAPINTS);
    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 == CPUID_LNX_5);
    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)
{
#define KVM_X86_TRANSLATE_FEATURE(f)    \
    case X86_FEATURE_##f: return KVM_X86_FEATURE_##f
 
    switch (x86_feature) {
    KVM_X86_TRANSLATE_FEATURE(SGX1);
    KVM_X86_TRANSLATE_FEATURE(SGX2);
    KVM_X86_TRANSLATE_FEATURE(SGX_EDECCSSA);
    KVM_X86_TRANSLATE_FEATURE(CONSTANT_TSC);
    KVM_X86_TRANSLATE_FEATURE(PERFMON_V2);
    KVM_X86_TRANSLATE_FEATURE(RRSBA_CTRL);
    KVM_X86_TRANSLATE_FEATURE(BHI_CTRL);
    default:
        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 */