GNU Linux-libre 6.1.24-gnu

[releases.git] / arch / x86 / kvm / cpuid.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Kernel-based Virtual Machine driver for Linux
 * cpuid support routines
 *
 * derived from arch/x86/kvm/x86.c
 *
 * Copyright 2011 Red Hat, Inc. and/or its affiliates.
 * Copyright IBM Corporation, 2008
 */

#include <linux/kvm_host.h>
#include <linux/export.h>
#include <linux/vmalloc.h>
#include <linux/uaccess.h>
#include <linux/sched/stat.h>

#include <asm/processor.h>
#include <asm/user.h>
#include <asm/fpu/xstate.h>
#include <asm/sgx.h>
#include <asm/cpuid.h>
#include "cpuid.h"
#include "lapic.h"
#include "mmu.h"
#include "trace.h"
#include "pmu.h"

/*
 * Unlike "struct cpuinfo_x86.x86_capability", kvm_cpu_caps doesn't need to be
 * aligned to sizeof(unsigned long) because it's not accessed via bitops.
 */
u32 kvm_cpu_caps[NR_KVM_CPU_CAPS] __read_mostly;
EXPORT_SYMBOL_GPL(kvm_cpu_caps);

u32 xstate_required_size(u64 xstate_bv, bool compacted)
{
        int feature_bit = 0;
        u32 ret = XSAVE_HDR_SIZE + XSAVE_HDR_OFFSET;

        xstate_bv &= XFEATURE_MASK_EXTEND;
        while (xstate_bv) {
                if (xstate_bv & 0x1) {
                        u32 eax, ebx, ecx, edx, offset;
                        cpuid_count(0xD, feature_bit, &eax, &ebx, &ecx, &edx);
                        /* ECX[1]: 64B alignment in compacted form */
                        if (compacted)
                                offset = (ecx & 0x2) ? ALIGN(ret, 64) : ret;
                        else
                                offset = ebx;
                        ret = max(ret, offset + eax);
                }

                xstate_bv >>= 1;
                feature_bit++;
        }

        return ret;
}

/*
 * This one is tied to SSB in the user API, and not
 * visible in /proc/cpuinfo.
 */
#define KVM_X86_FEATURE_PSFD            (13*32+28) /* Predictive Store Forwarding Disable */

#define F feature_bit
#define SF(name) (boot_cpu_has(X86_FEATURE_##name) ? F(name) : 0)

/*
 * Magic value used by KVM when querying userspace-provided CPUID entries and
 * doesn't care about the CPIUD index because the index of the function in
 * question is not significant.  Note, this magic value must have at least one
 * bit set in bits[63:32] and must be consumed as a u64 by cpuid_entry2_find()
 * to avoid false positives when processing guest CPUID input.
 */
#define KVM_CPUID_INDEX_NOT_SIGNIFICANT -1ull

static inline struct kvm_cpuid_entry2 *cpuid_entry2_find(
        struct kvm_cpuid_entry2 *entries, int nent, u32 function, u64 index)
{
        struct kvm_cpuid_entry2 *e;
        int i;

        for (i = 0; i < nent; i++) {
                e = &entries[i];

                if (e->function != function)
                        continue;

                /*
                 * If the index isn't significant, use the first entry with a
                 * matching function.  It's userspace's responsibilty to not
                 * provide "duplicate" entries in all cases.
                 */
                if (!(e->flags & KVM_CPUID_FLAG_SIGNIFCANT_INDEX) || e->index == index)
                        return e;


                /*
                 * Similarly, use the first matching entry if KVM is doing a
                 * lookup (as opposed to emulating CPUID) for a function that's
                 * architecturally defined as not having a significant index.
                 */
                if (index == KVM_CPUID_INDEX_NOT_SIGNIFICANT) {
                        /*
                         * Direct lookups from KVM should not diverge from what
                         * KVM defines internally (the architectural behavior).
                         */
                        WARN_ON_ONCE(cpuid_function_is_indexed(function));
                        return e;
                }
        }

        return NULL;
}

static int kvm_check_cpuid(struct kvm_vcpu *vcpu,
                           struct kvm_cpuid_entry2 *entries,
                           int nent)
{
        struct kvm_cpuid_entry2 *best;
        u64 xfeatures;

        /*
         * The existing code assumes virtual address is 48-bit or 57-bit in the
         * canonical address checks; exit if it is ever changed.
         */
        best = cpuid_entry2_find(entries, nent, 0x80000008,
                                 KVM_CPUID_INDEX_NOT_SIGNIFICANT);
        if (best) {
                int vaddr_bits = (best->eax & 0xff00) >> 8;

                if (vaddr_bits != 48 && vaddr_bits != 57 && vaddr_bits != 0)
                        return -EINVAL;
        }

        /*
         * Exposing dynamic xfeatures to the guest requires additional
         * enabling in the FPU, e.g. to expand the guest XSAVE state size.
         */
        best = cpuid_entry2_find(entries, nent, 0xd, 0);
        if (!best)
                return 0;

        xfeatures = best->eax | ((u64)best->edx << 32);
        xfeatures &= XFEATURE_MASK_USER_DYNAMIC;
        if (!xfeatures)
                return 0;

        return fpu_enable_guest_xfd_features(&vcpu->arch.guest_fpu, xfeatures);
}

/* Check whether the supplied CPUID data is equal to what is already set for the vCPU. */
static int kvm_cpuid_check_equal(struct kvm_vcpu *vcpu, struct kvm_cpuid_entry2 *e2,
                                 int nent)
{
        struct kvm_cpuid_entry2 *orig;
        int i;

        if (nent != vcpu->arch.cpuid_nent)
                return -EINVAL;

        for (i = 0; i < nent; i++) {
                orig = &vcpu->arch.cpuid_entries[i];
                if (e2[i].function != orig->function ||
                    e2[i].index != orig->index ||
                    e2[i].flags != orig->flags ||
                    e2[i].eax != orig->eax || e2[i].ebx != orig->ebx ||
                    e2[i].ecx != orig->ecx || e2[i].edx != orig->edx)
                        return -EINVAL;
        }

        return 0;
}

static void kvm_update_kvm_cpuid_base(struct kvm_vcpu *vcpu)
{
        u32 function;
        struct kvm_cpuid_entry2 *entry;

        vcpu->arch.kvm_cpuid_base = 0;

        for_each_possible_hypervisor_cpuid_base(function) {
                entry = kvm_find_cpuid_entry(vcpu, function);

                if (entry) {
                        u32 signature[3];

                        signature[0] = entry->ebx;
                        signature[1] = entry->ecx;
                        signature[2] = entry->edx;

                        BUILD_BUG_ON(sizeof(signature) > sizeof(KVM_SIGNATURE));
                        if (!memcmp(signature, KVM_SIGNATURE, sizeof(signature))) {
                                vcpu->arch.kvm_cpuid_base = function;
                                break;
                        }
                }
        }
}

static struct kvm_cpuid_entry2 *__kvm_find_kvm_cpuid_features(struct kvm_vcpu *vcpu,
                                              struct kvm_cpuid_entry2 *entries, int nent)
{
        u32 base = vcpu->arch.kvm_cpuid_base;

        if (!base)
                return NULL;

        return cpuid_entry2_find(entries, nent, base | KVM_CPUID_FEATURES,
                                 KVM_CPUID_INDEX_NOT_SIGNIFICANT);
}

static struct kvm_cpuid_entry2 *kvm_find_kvm_cpuid_features(struct kvm_vcpu *vcpu)
{
        return __kvm_find_kvm_cpuid_features(vcpu, vcpu->arch.cpuid_entries,
                                             vcpu->arch.cpuid_nent);
}

void kvm_update_pv_runtime(struct kvm_vcpu *vcpu)
{
        struct kvm_cpuid_entry2 *best = kvm_find_kvm_cpuid_features(vcpu);

        /*
         * save the feature bitmap to avoid cpuid lookup for every PV
         * operation
         */
        if (best)
                vcpu->arch.pv_cpuid.features = best->eax;
}

/*
 * Calculate guest's supported XCR0 taking into account guest CPUID data and
 * KVM's supported XCR0 (comprised of host's XCR0 and KVM_SUPPORTED_XCR0).
 */
static u64 cpuid_get_supported_xcr0(struct kvm_cpuid_entry2 *entries, int nent)
{
        struct kvm_cpuid_entry2 *best;

        best = cpuid_entry2_find(entries, nent, 0xd, 0);
        if (!best)
                return 0;

        return (best->eax | ((u64)best->edx << 32)) & kvm_caps.supported_xcr0;
}

static void __kvm_update_cpuid_runtime(struct kvm_vcpu *vcpu, struct kvm_cpuid_entry2 *entries,
                                       int nent)
{
        struct kvm_cpuid_entry2 *best;
        u64 guest_supported_xcr0 = cpuid_get_supported_xcr0(entries, nent);

        best = cpuid_entry2_find(entries, nent, 1, KVM_CPUID_INDEX_NOT_SIGNIFICANT);
        if (best) {
                /* Update OSXSAVE bit */
                if (boot_cpu_has(X86_FEATURE_XSAVE))
                        cpuid_entry_change(best, X86_FEATURE_OSXSAVE,
                                   kvm_read_cr4_bits(vcpu, X86_CR4_OSXSAVE));

                cpuid_entry_change(best, X86_FEATURE_APIC,
                           vcpu->arch.apic_base & MSR_IA32_APICBASE_ENABLE);
        }

        best = cpuid_entry2_find(entries, nent, 7, 0);
        if (best && boot_cpu_has(X86_FEATURE_PKU) && best->function == 0x7)
                cpuid_entry_change(best, X86_FEATURE_OSPKE,
                                   kvm_read_cr4_bits(vcpu, X86_CR4_PKE));

        best = cpuid_entry2_find(entries, nent, 0xD, 0);
        if (best)
                best->ebx = xstate_required_size(vcpu->arch.xcr0, false);

        best = cpuid_entry2_find(entries, nent, 0xD, 1);
        if (best && (cpuid_entry_has(best, X86_FEATURE_XSAVES) ||
                     cpuid_entry_has(best, X86_FEATURE_XSAVEC)))
                best->ebx = xstate_required_size(vcpu->arch.xcr0, true);

        best = __kvm_find_kvm_cpuid_features(vcpu, entries, nent);
        if (kvm_hlt_in_guest(vcpu->kvm) && best &&
                (best->eax & (1 << KVM_FEATURE_PV_UNHALT)))
                best->eax &= ~(1 << KVM_FEATURE_PV_UNHALT);

        if (!kvm_check_has_quirk(vcpu->kvm, KVM_X86_QUIRK_MISC_ENABLE_NO_MWAIT)) {
                best = cpuid_entry2_find(entries, nent, 0x1, KVM_CPUID_INDEX_NOT_SIGNIFICANT);
                if (best)
                        cpuid_entry_change(best, X86_FEATURE_MWAIT,
                                           vcpu->arch.ia32_misc_enable_msr &
                                           MSR_IA32_MISC_ENABLE_MWAIT);
        }

        /*
         * Bits 127:0 of the allowed SECS.ATTRIBUTES (CPUID.0x12.0x1) enumerate
         * the supported XSAVE Feature Request Mask (XFRM), i.e. the enclave's
         * requested XCR0 value.  The enclave's XFRM must be a subset of XCRO
         * at the time of EENTER, thus adjust the allowed XFRM by the guest's
         * supported XCR0.  Similar to XCR0 handling, FP and SSE are forced to
         * '1' even on CPUs that don't support XSAVE.
         */
        best = cpuid_entry2_find(entries, nent, 0x12, 0x1);
        if (best) {
                best->ecx &= guest_supported_xcr0 & 0xffffffff;
                best->edx &= guest_supported_xcr0 >> 32;
                best->ecx |= XFEATURE_MASK_FPSSE;
        }
}

void kvm_update_cpuid_runtime(struct kvm_vcpu *vcpu)
{
        __kvm_update_cpuid_runtime(vcpu, vcpu->arch.cpuid_entries, vcpu->arch.cpuid_nent);
}
EXPORT_SYMBOL_GPL(kvm_update_cpuid_runtime);

static bool kvm_cpuid_has_hyperv(struct kvm_cpuid_entry2 *entries, int nent)
{
        struct kvm_cpuid_entry2 *entry;

        entry = cpuid_entry2_find(entries, nent, HYPERV_CPUID_INTERFACE,
                                  KVM_CPUID_INDEX_NOT_SIGNIFICANT);
        return entry && entry->eax == HYPERV_CPUID_SIGNATURE_EAX;
}

static void kvm_vcpu_after_set_cpuid(struct kvm_vcpu *vcpu)
{
        struct kvm_lapic *apic = vcpu->arch.apic;
        struct kvm_cpuid_entry2 *best;

        best = kvm_find_cpuid_entry(vcpu, 1);
        if (best && apic) {
                if (cpuid_entry_has(best, X86_FEATURE_TSC_DEADLINE_TIMER))
                        apic->lapic_timer.timer_mode_mask = 3 << 17;
                else
                        apic->lapic_timer.timer_mode_mask = 1 << 17;

                kvm_apic_set_version(vcpu);
        }

        vcpu->arch.guest_supported_xcr0 =
                cpuid_get_supported_xcr0(vcpu->arch.cpuid_entries, vcpu->arch.cpuid_nent);

        /*
         * FP+SSE can always be saved/restored via KVM_{G,S}ET_XSAVE, even if
         * XSAVE/XCRO are not exposed to the guest, and even if XSAVE isn't
         * supported by the host.
         */
        vcpu->arch.guest_fpu.fpstate->user_xfeatures = vcpu->arch.guest_supported_xcr0 |
                                                       XFEATURE_MASK_FPSSE;

        kvm_update_pv_runtime(vcpu);

        vcpu->arch.maxphyaddr = cpuid_query_maxphyaddr(vcpu);
        vcpu->arch.reserved_gpa_bits = kvm_vcpu_reserved_gpa_bits_raw(vcpu);

        kvm_pmu_refresh(vcpu);
        vcpu->arch.cr4_guest_rsvd_bits =
            __cr4_reserved_bits(guest_cpuid_has, vcpu);

        kvm_hv_set_cpuid(vcpu, kvm_cpuid_has_hyperv(vcpu->arch.cpuid_entries,
                                                    vcpu->arch.cpuid_nent));

        /* Invoke the vendor callback only after the above state is updated. */
        static_call(kvm_x86_vcpu_after_set_cpuid)(vcpu);

        /*
         * Except for the MMU, which needs to do its thing any vendor specific
         * adjustments to the reserved GPA bits.
         */
        kvm_mmu_after_set_cpuid(vcpu);
}

int cpuid_query_maxphyaddr(struct kvm_vcpu *vcpu)
{
        struct kvm_cpuid_entry2 *best;

        best = kvm_find_cpuid_entry(vcpu, 0x80000000);
        if (!best || best->eax < 0x80000008)
                goto not_found;
        best = kvm_find_cpuid_entry(vcpu, 0x80000008);
        if (best)
                return best->eax & 0xff;
not_found:
        return 36;
}

/*
 * This "raw" version returns the reserved GPA bits without any adjustments for
 * encryption technologies that usurp bits.  The raw mask should be used if and
 * only if hardware does _not_ strip the usurped bits, e.g. in virtual MTRRs.
 */
u64 kvm_vcpu_reserved_gpa_bits_raw(struct kvm_vcpu *vcpu)
{
        return rsvd_bits(cpuid_maxphyaddr(vcpu), 63);
}

static int kvm_set_cpuid(struct kvm_vcpu *vcpu, struct kvm_cpuid_entry2 *e2,
                        int nent)
{
        int r;

        __kvm_update_cpuid_runtime(vcpu, e2, nent);

        /*
         * KVM does not correctly handle changing guest CPUID after KVM_RUN, as
         * MAXPHYADDR, GBPAGES support, AMD reserved bit behavior, etc.. aren't
         * tracked in kvm_mmu_page_role.  As a result, KVM may miss guest page
         * faults due to reusing SPs/SPTEs. In practice no sane VMM mucks with
         * the core vCPU model on the fly. It would've been better to forbid any
         * KVM_SET_CPUID{,2} calls after KVM_RUN altogether but unfortunately
         * some VMMs (e.g. QEMU) reuse vCPU fds for CPU hotplug/unplug and do
         * KVM_SET_CPUID{,2} again. To support this legacy behavior, check
         * whether the supplied CPUID data is equal to what's already set.
         */
        if (vcpu->arch.last_vmentry_cpu != -1) {
                r = kvm_cpuid_check_equal(vcpu, e2, nent);
                if (r)
                        return r;

                kvfree(e2);
                return 0;
        }

        if (kvm_cpuid_has_hyperv(e2, nent)) {
                r = kvm_hv_vcpu_init(vcpu);
                if (r)
                        return r;
        }

        r = kvm_check_cpuid(vcpu, e2, nent);
        if (r)
                return r;

        kvfree(vcpu->arch.cpuid_entries);
        vcpu->arch.cpuid_entries = e2;
        vcpu->arch.cpuid_nent = nent;

        kvm_update_kvm_cpuid_base(vcpu);
        kvm_vcpu_after_set_cpuid(vcpu);

        return 0;
}

/* when an old userspace process fills a new kernel module */
int kvm_vcpu_ioctl_set_cpuid(struct kvm_vcpu *vcpu,
                             struct kvm_cpuid *cpuid,
                             struct kvm_cpuid_entry __user *entries)
{
        int r, i;
        struct kvm_cpuid_entry *e = NULL;
        struct kvm_cpuid_entry2 *e2 = NULL;

        if (cpuid->nent > KVM_MAX_CPUID_ENTRIES)
                return -E2BIG;

        if (cpuid->nent) {
                e = vmemdup_user(entries, array_size(sizeof(*e), cpuid->nent));
                if (IS_ERR(e))
                        return PTR_ERR(e);

                e2 = kvmalloc_array(cpuid->nent, sizeof(*e2), GFP_KERNEL_ACCOUNT);
                if (!e2) {
                        r = -ENOMEM;
                        goto out_free_cpuid;
                }
        }
        for (i = 0; i < cpuid->nent; i++) {
                e2[i].function = e[i].function;
                e2[i].eax = e[i].eax;
                e2[i].ebx = e[i].ebx;
                e2[i].ecx = e[i].ecx;
                e2[i].edx = e[i].edx;
                e2[i].index = 0;
                e2[i].flags = 0;
                e2[i].padding[0] = 0;
                e2[i].padding[1] = 0;
                e2[i].padding[2] = 0;
        }

        r = kvm_set_cpuid(vcpu, e2, cpuid->nent);
        if (r)
                kvfree(e2);

out_free_cpuid:
        kvfree(e);

        return r;
}

int kvm_vcpu_ioctl_set_cpuid2(struct kvm_vcpu *vcpu,
                              struct kvm_cpuid2 *cpuid,
                              struct kvm_cpuid_entry2 __user *entries)
{
        struct kvm_cpuid_entry2 *e2 = NULL;
        int r;

        if (cpuid->nent > KVM_MAX_CPUID_ENTRIES)
                return -E2BIG;

        if (cpuid->nent) {
                e2 = vmemdup_user(entries, array_size(sizeof(*e2), cpuid->nent));
                if (IS_ERR(e2))
                        return PTR_ERR(e2);
        }

        r = kvm_set_cpuid(vcpu, e2, cpuid->nent);
        if (r)
                kvfree(e2);

        return r;
}

int kvm_vcpu_ioctl_get_cpuid2(struct kvm_vcpu *vcpu,
                              struct kvm_cpuid2 *cpuid,
                              struct kvm_cpuid_entry2 __user *entries)
{
        int r;

        r = -E2BIG;
        if (cpuid->nent < vcpu->arch.cpuid_nent)
                goto out;
        r = -EFAULT;
        if (copy_to_user(entries, vcpu->arch.cpuid_entries,
                         vcpu->arch.cpuid_nent * sizeof(struct kvm_cpuid_entry2)))
                goto out;
        return 0;

out:
        cpuid->nent = vcpu->arch.cpuid_nent;
        return r;
}

/* Mask kvm_cpu_caps for @leaf with the raw CPUID capabilities of this CPU. */
static __always_inline void __kvm_cpu_cap_mask(unsigned int leaf)
{
        const struct cpuid_reg cpuid = x86_feature_cpuid(leaf * 32);
        struct kvm_cpuid_entry2 entry;

        reverse_cpuid_check(leaf);

        cpuid_count(cpuid.function, cpuid.index,
                    &entry.eax, &entry.ebx, &entry.ecx, &entry.edx);

        kvm_cpu_caps[leaf] &= *__cpuid_entry_get_reg(&entry, cpuid.reg);
}

static __always_inline
void kvm_cpu_cap_init_scattered(enum kvm_only_cpuid_leafs leaf, u32 mask)
{
        /* Use kvm_cpu_cap_mask for non-scattered leafs. */
        BUILD_BUG_ON(leaf < NCAPINTS);

        kvm_cpu_caps[leaf] = mask;

        __kvm_cpu_cap_mask(leaf);
}

static __always_inline void kvm_cpu_cap_mask(enum cpuid_leafs leaf, u32 mask)
{
        /* Use kvm_cpu_cap_init_scattered for scattered leafs. */
        BUILD_BUG_ON(leaf >= NCAPINTS);

        kvm_cpu_caps[leaf] &= mask;

        __kvm_cpu_cap_mask(leaf);
}

void kvm_set_cpu_caps(void)
{
#ifdef CONFIG_X86_64
        unsigned int f_gbpages = F(GBPAGES);
        unsigned int f_lm = F(LM);
        unsigned int f_xfd = F(XFD);
#else
        unsigned int f_gbpages = 0;
        unsigned int f_lm = 0;
        unsigned int f_xfd = 0;
#endif
        memset(kvm_cpu_caps, 0, sizeof(kvm_cpu_caps));

        BUILD_BUG_ON(sizeof(kvm_cpu_caps) - (NKVMCAPINTS * sizeof(*kvm_cpu_caps)) >
                     sizeof(boot_cpu_data.x86_capability));

        memcpy(&kvm_cpu_caps, &boot_cpu_data.x86_capability,
               sizeof(kvm_cpu_caps) - (NKVMCAPINTS * sizeof(*kvm_cpu_caps)));

        kvm_cpu_cap_mask(CPUID_1_ECX,
                /*
                 * NOTE: MONITOR (and MWAIT) are emulated as NOP, but *not*
                 * advertised to guests via CPUID!
                 */
                F(XMM3) | F(PCLMULQDQ) | 0 /* DTES64, MONITOR */ |
                0 /* DS-CPL, VMX, SMX, EST */ |
                0 /* TM2 */ | F(SSSE3) | 0 /* CNXT-ID */ | 0 /* Reserved */ |
                F(FMA) | F(CX16) | 0 /* xTPR Update */ | F(PDCM) |
                F(PCID) | 0 /* Reserved, DCA */ | F(XMM4_1) |
                F(XMM4_2) | F(X2APIC) | F(MOVBE) | F(POPCNT) |
                0 /* Reserved*/ | F(AES) | F(XSAVE) | 0 /* OSXSAVE */ | F(AVX) |
                F(F16C) | F(RDRAND)
        );
        /* KVM emulates x2apic in software irrespective of host support. */
        kvm_cpu_cap_set(X86_FEATURE_X2APIC);

        kvm_cpu_cap_mask(CPUID_1_EDX,
                F(FPU) | F(VME) | F(DE) | F(PSE) |
                F(TSC) | F(MSR) | F(PAE) | F(MCE) |
                F(CX8) | F(APIC) | 0 /* Reserved */ | F(SEP) |
                F(MTRR) | F(PGE) | F(MCA) | F(CMOV) |
                F(PAT) | F(PSE36) | 0 /* PSN */ | F(CLFLUSH) |
                0 /* Reserved, DS, ACPI */ | F(MMX) |
                F(FXSR) | F(XMM) | F(XMM2) | F(SELFSNOOP) |
                0 /* HTT, TM, Reserved, PBE */
        );

        kvm_cpu_cap_mask(CPUID_7_0_EBX,
                F(FSGSBASE) | F(SGX) | F(BMI1) | F(HLE) | F(AVX2) |
                F(FDP_EXCPTN_ONLY) | F(SMEP) | F(BMI2) | F(ERMS) | F(INVPCID) |
                F(RTM) | F(ZERO_FCS_FDS) | 0 /*MPX*/ | F(AVX512F) |
                F(AVX512DQ) | F(RDSEED) | F(ADX) | F(SMAP) | F(AVX512IFMA) |
                F(CLFLUSHOPT) | F(CLWB) | 0 /*INTEL_PT*/ | F(AVX512PF) |
                F(AVX512ER) | F(AVX512CD) | F(SHA_NI) | F(AVX512BW) |
                F(AVX512VL));

        kvm_cpu_cap_mask(CPUID_7_ECX,
                F(AVX512VBMI) | F(LA57) | F(PKU) | 0 /*OSPKE*/ | F(RDPID) |
                F(AVX512_VPOPCNTDQ) | F(UMIP) | F(AVX512_VBMI2) | F(GFNI) |
                F(VAES) | F(VPCLMULQDQ) | F(AVX512_VNNI) | F(AVX512_BITALG) |
                F(CLDEMOTE) | F(MOVDIRI) | F(MOVDIR64B) | 0 /*WAITPKG*/ |
                F(SGX_LC) | F(BUS_LOCK_DETECT)
        );
        /* Set LA57 based on hardware capability. */
        if (cpuid_ecx(7) & F(LA57))
                kvm_cpu_cap_set(X86_FEATURE_LA57);

        /*
         * PKU not yet implemented for shadow paging and requires OSPKE
         * to be set on the host. Clear it if that is not the case
         */
        if (!tdp_enabled || !boot_cpu_has(X86_FEATURE_OSPKE))
                kvm_cpu_cap_clear(X86_FEATURE_PKU);

        kvm_cpu_cap_mask(CPUID_7_EDX,
                F(AVX512_4VNNIW) | F(AVX512_4FMAPS) | F(SPEC_CTRL) |
                F(SPEC_CTRL_SSBD) | F(ARCH_CAPABILITIES) | F(INTEL_STIBP) |
                F(MD_CLEAR) | F(AVX512_VP2INTERSECT) | F(FSRM) |
                F(SERIALIZE) | F(TSXLDTRK) | F(AVX512_FP16) |
                F(AMX_TILE) | F(AMX_INT8) | F(AMX_BF16)
        );

        /* TSC_ADJUST and ARCH_CAPABILITIES are emulated in software. */
        kvm_cpu_cap_set(X86_FEATURE_TSC_ADJUST);
        kvm_cpu_cap_set(X86_FEATURE_ARCH_CAPABILITIES);

        if (boot_cpu_has(X86_FEATURE_IBPB) && boot_cpu_has(X86_FEATURE_IBRS))
                kvm_cpu_cap_set(X86_FEATURE_SPEC_CTRL);
        if (boot_cpu_has(X86_FEATURE_STIBP))
                kvm_cpu_cap_set(X86_FEATURE_INTEL_STIBP);
        if (boot_cpu_has(X86_FEATURE_AMD_SSBD))
                kvm_cpu_cap_set(X86_FEATURE_SPEC_CTRL_SSBD);

        kvm_cpu_cap_mask(CPUID_7_1_EAX,
                F(AVX_VNNI) | F(AVX512_BF16)
        );

        kvm_cpu_cap_mask(CPUID_D_1_EAX,
                F(XSAVEOPT) | F(XSAVEC) | F(XGETBV1) | F(XSAVES) | f_xfd
        );

        kvm_cpu_cap_init_scattered(CPUID_12_EAX,
                SF(SGX1) | SF(SGX2)
        );

        kvm_cpu_cap_mask(CPUID_8000_0001_ECX,
                F(LAHF_LM) | F(CMP_LEGACY) | 0 /*SVM*/ | 0 /* ExtApicSpace */ |
                F(CR8_LEGACY) | F(ABM) | F(SSE4A) | F(MISALIGNSSE) |
                F(3DNOWPREFETCH) | F(OSVW) | 0 /* IBS */ | F(XOP) |
                0 /* SKINIT, WDT, LWP */ | F(FMA4) | F(TBM) |
                F(TOPOEXT) | 0 /* PERFCTR_CORE */
        );

        kvm_cpu_cap_mask(CPUID_8000_0001_EDX,
                F(FPU) | F(VME) | F(DE) | F(PSE) |
                F(TSC) | F(MSR) | F(PAE) | F(MCE) |
                F(CX8) | F(APIC) | 0 /* Reserved */ | F(SYSCALL) |
                F(MTRR) | F(PGE) | F(MCA) | F(CMOV) |
                F(PAT) | F(PSE36) | 0 /* Reserved */ |
                F(NX) | 0 /* Reserved */ | F(MMXEXT) | F(MMX) |
                F(FXSR) | F(FXSR_OPT) | f_gbpages | F(RDTSCP) |
                0 /* Reserved */ | f_lm | F(3DNOWEXT) | F(3DNOW)
        );

        if (!tdp_enabled && IS_ENABLED(CONFIG_X86_64))
                kvm_cpu_cap_set(X86_FEATURE_GBPAGES);

        kvm_cpu_cap_mask(CPUID_8000_0008_EBX,
                F(CLZERO) | F(XSAVEERPTR) |
                F(WBNOINVD) | F(AMD_IBPB) | F(AMD_IBRS) | F(AMD_SSBD) | F(VIRT_SSBD) |
                F(AMD_SSB_NO) | F(AMD_STIBP) | F(AMD_STIBP_ALWAYS_ON) |
                __feature_bit(KVM_X86_FEATURE_PSFD)
        );

        /*
         * AMD has separate bits for each SPEC_CTRL bit.
         * arch/x86/kernel/cpu/bugs.c is kind enough to
         * record that in cpufeatures so use them.
         */
        if (boot_cpu_has(X86_FEATURE_IBPB))
                kvm_cpu_cap_set(X86_FEATURE_AMD_IBPB);
        if (boot_cpu_has(X86_FEATURE_IBRS))
                kvm_cpu_cap_set(X86_FEATURE_AMD_IBRS);
        if (boot_cpu_has(X86_FEATURE_STIBP))
                kvm_cpu_cap_set(X86_FEATURE_AMD_STIBP);
        if (boot_cpu_has(X86_FEATURE_SPEC_CTRL_SSBD))
                kvm_cpu_cap_set(X86_FEATURE_AMD_SSBD);
        if (!boot_cpu_has_bug(X86_BUG_SPEC_STORE_BYPASS))
                kvm_cpu_cap_set(X86_FEATURE_AMD_SSB_NO);
        /*
         * The preference is to use SPEC CTRL MSR instead of the
         * VIRT_SPEC MSR.
         */
        if (boot_cpu_has(X86_FEATURE_LS_CFG_SSBD) &&
            !boot_cpu_has(X86_FEATURE_AMD_SSBD))
                kvm_cpu_cap_set(X86_FEATURE_VIRT_SSBD);

        /*
         * Hide all SVM features by default, SVM will set the cap bits for
         * features it emulates and/or exposes for L1.
         */
        kvm_cpu_cap_mask(CPUID_8000_000A_EDX, 0);

        kvm_cpu_cap_mask(CPUID_8000_001F_EAX,
                0 /* SME */ | F(SEV) | 0 /* VM_PAGE_FLUSH */ | F(SEV_ES) |
                F(SME_COHERENT));

        kvm_cpu_cap_mask(CPUID_C000_0001_EDX,
                F(XSTORE) | F(XSTORE_EN) | F(XCRYPT) | F(XCRYPT_EN) |
                F(ACE2) | F(ACE2_EN) | F(PHE) | F(PHE_EN) |
                F(PMM) | F(PMM_EN)
        );

        /*
         * Hide RDTSCP and RDPID if either feature is reported as supported but
         * probing MSR_TSC_AUX failed.  This is purely a sanity check and
         * should never happen, but the guest will likely crash if RDTSCP or
         * RDPID is misreported, and KVM has botched MSR_TSC_AUX emulation in
         * the past.  For example, the sanity check may fire if this instance of
         * KVM is running as L1 on top of an older, broken KVM.
         */
        if (WARN_ON((kvm_cpu_cap_has(X86_FEATURE_RDTSCP) ||
                     kvm_cpu_cap_has(X86_FEATURE_RDPID)) &&
                     !kvm_is_supported_user_return_msr(MSR_TSC_AUX))) {
                kvm_cpu_cap_clear(X86_FEATURE_RDTSCP);
                kvm_cpu_cap_clear(X86_FEATURE_RDPID);
        }
}
EXPORT_SYMBOL_GPL(kvm_set_cpu_caps);

struct kvm_cpuid_array {
        struct kvm_cpuid_entry2 *entries;
        int maxnent;
        int nent;
};

static struct kvm_cpuid_entry2 *get_next_cpuid(struct kvm_cpuid_array *array)
{
        if (array->nent >= array->maxnent)
                return NULL;

        return &array->entries[array->nent++];
}

static struct kvm_cpuid_entry2 *do_host_cpuid(struct kvm_cpuid_array *array,
                                              u32 function, u32 index)
{
        struct kvm_cpuid_entry2 *entry = get_next_cpuid(array);

        if (!entry)
                return NULL;

        memset(entry, 0, sizeof(*entry));
        entry->function = function;
        entry->index = index;
        switch (function & 0xC0000000) {
        case 0x40000000:
                /* Hypervisor leaves are always synthesized by __do_cpuid_func.  */
                return entry;

        case 0x80000000:
                /*
                 * 0x80000021 is sometimes synthesized by __do_cpuid_func, which
                 * would result in out-of-bounds calls to do_host_cpuid.
                 */
                {
                        static int max_cpuid_80000000;
                        if (!READ_ONCE(max_cpuid_80000000))
                                WRITE_ONCE(max_cpuid_80000000, cpuid_eax(0x80000000));
                        if (function > READ_ONCE(max_cpuid_80000000))
                                return entry;
                }
                break;

        default:
                break;
        }

        cpuid_count(entry->function, entry->index,
                    &entry->eax, &entry->ebx, &entry->ecx, &entry->edx);

        if (cpuid_function_is_indexed(function))
                entry->flags |= KVM_CPUID_FLAG_SIGNIFCANT_INDEX;

        return entry;
}

static int __do_cpuid_func_emulated(struct kvm_cpuid_array *array, u32 func)
{
        struct kvm_cpuid_entry2 *entry;

        if (array->nent >= array->maxnent)
                return -E2BIG;

        entry = &array->entries[array->nent];
        entry->function = func;
        entry->index = 0;
        entry->flags = 0;

        switch (func) {
        case 0:
                entry->eax = 7;
                ++array->nent;
                break;
        case 1:
                entry->ecx = F(MOVBE);
                ++array->nent;
                break;
        case 7:
                entry->flags |= KVM_CPUID_FLAG_SIGNIFCANT_INDEX;
                entry->eax = 0;
                if (kvm_cpu_cap_has(X86_FEATURE_RDTSCP))
                        entry->ecx = F(RDPID);
                ++array->nent;
                break;
        default:
                break;
        }

        return 0;
}

static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function)
{
        struct kvm_cpuid_entry2 *entry;
        int r, i, max_idx;

        /* all calls to cpuid_count() should be made on the same cpu */
        get_cpu();

        r = -E2BIG;

        entry = do_host_cpuid(array, function, 0);
        if (!entry)
                goto out;

        switch (function) {
        case 0:
                /* Limited to the highest leaf implemented in KVM. */
                entry->eax = min(entry->eax, 0x1fU);
                break;
        case 1:
                cpuid_entry_override(entry, CPUID_1_EDX);
                cpuid_entry_override(entry, CPUID_1_ECX);
                break;
        case 2:
                /*
                 * On ancient CPUs, function 2 entries are STATEFUL.  That is,
                 * CPUID(function=2, index=0) may return different results each
                 * time, with the least-significant byte in EAX enumerating the
                 * number of times software should do CPUID(2, 0).
                 *
                 * Modern CPUs, i.e. every CPU KVM has *ever* run on are less
                 * idiotic.  Intel's SDM states that EAX & 0xff "will always
                 * return 01H. Software should ignore this value and not
                 * interpret it as an informational descriptor", while AMD's
                 * APM states that CPUID(2) is reserved.
                 *
                 * WARN if a frankenstein CPU that supports virtualization and
                 * a stateful CPUID.0x2 is encountered.
                 */
                WARN_ON_ONCE((entry->eax & 0xff) > 1);
                break;
        /* functions 4 and 0x8000001d have additional index. */
        case 4:
        case 0x8000001d:
                /*
                 * Read entries until the cache type in the previous entry is
                 * zero, i.e. indicates an invalid entry.
                 */
                for (i = 1; entry->eax & 0x1f; ++i) {
                        entry = do_host_cpuid(array, function, i);
                        if (!entry)
                                goto out;
                }
                break;
        case 6: /* Thermal management */
                entry->eax = 0x4; /* allow ARAT */
                entry->ebx = 0;
                entry->ecx = 0;
                entry->edx = 0;
                break;
        /* function 7 has additional index. */
        case 7:
                entry->eax = min(entry->eax, 1u);
                cpuid_entry_override(entry, CPUID_7_0_EBX);
                cpuid_entry_override(entry, CPUID_7_ECX);
                cpuid_entry_override(entry, CPUID_7_EDX);

                /* KVM only supports 0x7.0 and 0x7.1, capped above via min(). */
                if (entry->eax == 1) {
                        entry = do_host_cpuid(array, function, 1);
                        if (!entry)
                                goto out;

                        cpuid_entry_override(entry, CPUID_7_1_EAX);
                        entry->ebx = 0;
                        entry->ecx = 0;
                        entry->edx = 0;
                }
                break;
        case 0xa: { /* Architectural Performance Monitoring */
                union cpuid10_eax eax;
                union cpuid10_edx edx;

                if (!static_cpu_has(X86_FEATURE_ARCH_PERFMON)) {
                        entry->eax = entry->ebx = entry->ecx = entry->edx = 0;
                        break;
                }

                eax.split.version_id = kvm_pmu_cap.version;
                eax.split.num_counters = kvm_pmu_cap.num_counters_gp;
                eax.split.bit_width = kvm_pmu_cap.bit_width_gp;
                eax.split.mask_length = kvm_pmu_cap.events_mask_len;
                edx.split.num_counters_fixed = kvm_pmu_cap.num_counters_fixed;
                edx.split.bit_width_fixed = kvm_pmu_cap.bit_width_fixed;

                if (kvm_pmu_cap.version)
                        edx.split.anythread_deprecated = 1;
                edx.split.reserved1 = 0;
                edx.split.reserved2 = 0;

                entry->eax = eax.full;
                entry->ebx = kvm_pmu_cap.events_mask;
                entry->ecx = 0;
                entry->edx = edx.full;
                break;
        }
        case 0x1f:
        case 0xb:
                /*
                 * No topology; a valid topology is indicated by the presence
                 * of subleaf 1.
                 */
                entry->eax = entry->ebx = entry->ecx = 0;
                break;
        case 0xd: {
                u64 permitted_xcr0 = kvm_caps.supported_xcr0 & xstate_get_guest_group_perm();
                u64 permitted_xss = kvm_caps.supported_xss;

                entry->eax &= permitted_xcr0;
                entry->ebx = xstate_required_size(permitted_xcr0, false);
                entry->ecx = entry->ebx;
                entry->edx &= permitted_xcr0 >> 32;
                if (!permitted_xcr0)
                        break;

                entry = do_host_cpuid(array, function, 1);
                if (!entry)
                        goto out;

                cpuid_entry_override(entry, CPUID_D_1_EAX);
                if (entry->eax & (F(XSAVES)|F(XSAVEC)))
                        entry->ebx = xstate_required_size(permitted_xcr0 | permitted_xss,
                                                          true);
                else {
                        WARN_ON_ONCE(permitted_xss != 0);
                        entry->ebx = 0;
                }
                entry->ecx &= permitted_xss;
                entry->edx &= permitted_xss >> 32;

                for (i = 2; i < 64; ++i) {
                        bool s_state;
                        if (permitted_xcr0 & BIT_ULL(i))
                                s_state = false;
                        else if (permitted_xss & BIT_ULL(i))
                                s_state = true;
                        else
                                continue;

                        entry = do_host_cpuid(array, function, i);
                        if (!entry)
                                goto out;

                        /*
                         * The supported check above should have filtered out
                         * invalid sub-leafs.  Only valid sub-leafs should
                         * reach this point, and they should have a non-zero
                         * save state size.  Furthermore, check whether the
                         * processor agrees with permitted_xcr0/permitted_xss
                         * on whether this is an XCR0- or IA32_XSS-managed area.
                         */
                        if (WARN_ON_ONCE(!entry->eax || (entry->ecx & 0x1) != s_state)) {
                                --array->nent;
                                continue;
                        }

                        if (!kvm_cpu_cap_has(X86_FEATURE_XFD))
                                entry->ecx &= ~BIT_ULL(2);
                        entry->edx = 0;
                }
                break;
        }
        case 0x12:
                /* Intel SGX */
                if (!kvm_cpu_cap_has(X86_FEATURE_SGX)) {
                        entry->eax = entry->ebx = entry->ecx = entry->edx = 0;
                        break;
                }

                /*
                 * Index 0: Sub-features, MISCSELECT (a.k.a extended features)
                 * and max enclave sizes.   The SGX sub-features and MISCSELECT
                 * are restricted by kernel and KVM capabilities (like most
                 * feature flags), while enclave size is unrestricted.
                 */
                cpuid_entry_override(entry, CPUID_12_EAX);
                entry->ebx &= SGX_MISC_EXINFO;

                entry = do_host_cpuid(array, function, 1);
                if (!entry)
                        goto out;

                /*
                 * Index 1: SECS.ATTRIBUTES.  ATTRIBUTES are restricted a la
                 * feature flags.  Advertise all supported flags, including
                 * privileged attributes that require explicit opt-in from
                 * userspace.  ATTRIBUTES.XFRM is not adjusted as userspace is
                 * expected to derive it from supported XCR0.
                 */
                entry->eax &= SGX_ATTR_DEBUG | SGX_ATTR_MODE64BIT |
                              SGX_ATTR_PROVISIONKEY | SGX_ATTR_EINITTOKENKEY |
                              SGX_ATTR_KSS;
                entry->ebx &= 0;
                break;
        /* Intel PT */
        case 0x14:
                if (!kvm_cpu_cap_has(X86_FEATURE_INTEL_PT)) {
                        entry->eax = entry->ebx = entry->ecx = entry->edx = 0;
                        break;
                }

                for (i = 1, max_idx = entry->eax; i <= max_idx; ++i) {
                        if (!do_host_cpuid(array, function, i))
                                goto out;
                }
                break;
        /* Intel AMX TILE */
        case 0x1d:
                if (!kvm_cpu_cap_has(X86_FEATURE_AMX_TILE)) {
                        entry->eax = entry->ebx = entry->ecx = entry->edx = 0;
                        break;
                }

                for (i = 1, max_idx = entry->eax; i <= max_idx; ++i) {
                        if (!do_host_cpuid(array, function, i))
                                goto out;
                }
                break;
        case 0x1e: /* TMUL information */
                if (!kvm_cpu_cap_has(X86_FEATURE_AMX_TILE)) {
                        entry->eax = entry->ebx = entry->ecx = entry->edx = 0;
                        break;
                }
                break;
        case KVM_CPUID_SIGNATURE: {
                const u32 *sigptr = (const u32 *)KVM_SIGNATURE;
                entry->eax = KVM_CPUID_FEATURES;
                entry->ebx = sigptr[0];
                entry->ecx = sigptr[1];
                entry->edx = sigptr[2];
                break;
        }
        case KVM_CPUID_FEATURES:
                entry->eax = (1 << KVM_FEATURE_CLOCKSOURCE) |
                             (1 << KVM_FEATURE_NOP_IO_DELAY) |
                             (1 << KVM_FEATURE_CLOCKSOURCE2) |
                             (1 << KVM_FEATURE_ASYNC_PF) |
                             (1 << KVM_FEATURE_PV_EOI) |
                             (1 << KVM_FEATURE_CLOCKSOURCE_STABLE_BIT) |
                             (1 << KVM_FEATURE_PV_UNHALT) |
                             (1 << KVM_FEATURE_PV_TLB_FLUSH) |
                             (1 << KVM_FEATURE_ASYNC_PF_VMEXIT) |
                             (1 << KVM_FEATURE_PV_SEND_IPI) |
                             (1 << KVM_FEATURE_POLL_CONTROL) |
                             (1 << KVM_FEATURE_PV_SCHED_YIELD) |
                             (1 << KVM_FEATURE_ASYNC_PF_INT);

                if (sched_info_on())
                        entry->eax |= (1 << KVM_FEATURE_STEAL_TIME);

                entry->ebx = 0;
                entry->ecx = 0;
                entry->edx = 0;
                break;
        case 0x80000000:
                entry->eax = min(entry->eax, 0x80000021);
                /*
                 * Serializing LFENCE is reported in a multitude of ways, and
                 * NullSegClearsBase is not reported in CPUID on Zen2; help
                 * userspace by providing the CPUID leaf ourselves.
                 *
                 * However, only do it if the host has CPUID leaf 0x8000001d.
                 * QEMU thinks that it can query the host blindly for that
                 * CPUID leaf if KVM reports that it supports 0x8000001d or
                 * above.  The processor merrily returns values from the
                 * highest Intel leaf which QEMU tries to use as the guest's
                 * 0x8000001d.  Even worse, this can result in an infinite
                 * loop if said highest leaf has no subleaves indexed by ECX.
                 */
                if (entry->eax >= 0x8000001d &&
                    (static_cpu_has(X86_FEATURE_LFENCE_RDTSC)
                     || !static_cpu_has_bug(X86_BUG_NULL_SEG)))
                        entry->eax = max(entry->eax, 0x80000021);
                break;
        case 0x80000001:
                entry->ebx &= ~GENMASK(27, 16);
                cpuid_entry_override(entry, CPUID_8000_0001_EDX);
                cpuid_entry_override(entry, CPUID_8000_0001_ECX);
                break;
        case 0x80000006:
                /* Drop reserved bits, pass host L2 cache and TLB info. */
                entry->edx &= ~GENMASK(17, 16);
                break;
        case 0x80000007: /* Advanced power management */
                /* invariant TSC is CPUID.80000007H:EDX[8] */
                entry->edx &= (1 << 8);
                /* mask against host */
                entry->edx &= boot_cpu_data.x86_power;
                entry->eax = entry->ebx = entry->ecx = 0;
                break;
        case 0x80000008: {
                unsigned g_phys_as = (entry->eax >> 16) & 0xff;
                unsigned virt_as = max((entry->eax >> 8) & 0xff, 48U);
                unsigned phys_as = entry->eax & 0xff;

                /*
                 * If TDP (NPT) is disabled use the adjusted host MAXPHYADDR as
                 * the guest operates in the same PA space as the host, i.e.
                 * reductions in MAXPHYADDR for memory encryption affect shadow
                 * paging, too.
                 *
                 * If TDP is enabled but an explicit guest MAXPHYADDR is not
                 * provided, use the raw bare metal MAXPHYADDR as reductions to
                 * the HPAs do not affect GPAs.
                 */
                if (!tdp_enabled)
                        g_phys_as = boot_cpu_data.x86_phys_bits;
                else if (!g_phys_as)
                        g_phys_as = phys_as;

                entry->eax = g_phys_as | (virt_as << 8);
                entry->ecx &= ~(GENMASK(31, 16) | GENMASK(11, 8));
                entry->edx = 0;
                cpuid_entry_override(entry, CPUID_8000_0008_EBX);
                break;
        }
        case 0x8000000A:
                if (!kvm_cpu_cap_has(X86_FEATURE_SVM)) {
                        entry->eax = entry->ebx = entry->ecx = entry->edx = 0;
                        break;
                }
                entry->eax = 1; /* SVM revision 1 */
                entry->ebx = 8; /* Lets support 8 ASIDs in case we add proper
                                   ASID emulation to nested SVM */
                entry->ecx = 0; /* Reserved */
                cpuid_entry_override(entry, CPUID_8000_000A_EDX);
                break;
        case 0x80000019:
                entry->ecx = entry->edx = 0;
                break;
        case 0x8000001a:
                entry->eax &= GENMASK(2, 0);
                entry->ebx = entry->ecx = entry->edx = 0;
                break;
        case 0x8000001e:
                /* Do not return host topology information.  */
                entry->eax = entry->ebx = entry->ecx = 0;
                entry->edx = 0; /* reserved */
                break;
        case 0x8000001F:
                if (!kvm_cpu_cap_has(X86_FEATURE_SEV)) {
                        entry->eax = entry->ebx = entry->ecx = entry->edx = 0;
                } else {
                        cpuid_entry_override(entry, CPUID_8000_001F_EAX);
                        /* Clear NumVMPL since KVM does not support VMPL.  */
                        entry->ebx &= ~GENMASK(31, 12);
                        /*
                         * Enumerate '0' for "PA bits reduction", the adjusted
                         * MAXPHYADDR is enumerated directly (see 0x80000008).
                         */
                        entry->ebx &= ~GENMASK(11, 6);
                }
                break;
        case 0x80000020:
                entry->eax = entry->ebx = entry->ecx = entry->edx = 0;
                break;
        case 0x80000021:
                entry->ebx = entry->ecx = entry->edx = 0;
                /*
                 * Pass down these bits:
                 *    EAX      0      NNDBP, Processor ignores nested data breakpoints
                 *    EAX      2      LAS, LFENCE always serializing
                 *    EAX      6      NSCB, Null selector clear base
                 *
                 * Other defined bits are for MSRs that KVM does not expose:
                 *   EAX      3      SPCL, SMM page configuration lock
                 *   EAX      13     PCMSR, Prefetch control MSR
                 */
                entry->eax &= BIT(0) | BIT(2) | BIT(6);
                if (static_cpu_has(X86_FEATURE_LFENCE_RDTSC))
                        entry->eax |= BIT(2);
                if (!static_cpu_has_bug(X86_BUG_NULL_SEG))
                        entry->eax |= BIT(6);
                break;
        /*Add support for Centaur's CPUID instruction*/
        case 0xC0000000:
                /*Just support up to 0xC0000004 now*/
                entry->eax = min(entry->eax, 0xC0000004);
                break;
        case 0xC0000001:
                cpuid_entry_override(entry, CPUID_C000_0001_EDX);
                break;
        case 3: /* Processor serial number */
        case 5: /* MONITOR/MWAIT */
        case 0xC0000002:
        case 0xC0000003:
        case 0xC0000004:
        default:
                entry->eax = entry->ebx = entry->ecx = entry->edx = 0;
                break;
        }

        r = 0;

out:
        put_cpu();

        return r;
}

static int do_cpuid_func(struct kvm_cpuid_array *array, u32 func,
                         unsigned int type)
{
        if (type == KVM_GET_EMULATED_CPUID)
                return __do_cpuid_func_emulated(array, func);

        return __do_cpuid_func(array, func);
}

#define CENTAUR_CPUID_SIGNATURE 0xC0000000

static int get_cpuid_func(struct kvm_cpuid_array *array, u32 func,
                          unsigned int type)
{
        u32 limit;
        int r;

        if (func == CENTAUR_CPUID_SIGNATURE &&
            boot_cpu_data.x86_vendor != X86_VENDOR_CENTAUR)
                return 0;

        r = do_cpuid_func(array, func, type);
        if (r)
                return r;

        limit = array->entries[array->nent - 1].eax;
        for (func = func + 1; func <= limit; ++func) {
                r = do_cpuid_func(array, func, type);
                if (r)
                        break;
        }

        return r;
}

static bool sanity_check_entries(struct kvm_cpuid_entry2 __user *entries,
                                 __u32 num_entries, unsigned int ioctl_type)
{
        int i;
        __u32 pad[3];

        if (ioctl_type != KVM_GET_EMULATED_CPUID)
                return false;

        /*
         * We want to make sure that ->padding is being passed clean from
         * userspace in case we want to use it for something in the future.
         *
         * Sadly, this wasn't enforced for KVM_GET_SUPPORTED_CPUID and so we
         * have to give ourselves satisfied only with the emulated side. /me
         * sheds a tear.
         */
        for (i = 0; i < num_entries; i++) {
                if (copy_from_user(pad, entries[i].padding, sizeof(pad)))
                        return true;

                if (pad[0] || pad[1] || pad[2])
                        return true;
        }
        return false;
}

int kvm_dev_ioctl_get_cpuid(struct kvm_cpuid2 *cpuid,
                            struct kvm_cpuid_entry2 __user *entries,
                            unsigned int type)
{
        static const u32 funcs[] = {
                0, 0x80000000, CENTAUR_CPUID_SIGNATURE, KVM_CPUID_SIGNATURE,
        };

        struct kvm_cpuid_array array = {
                .nent = 0,
        };
        int r, i;

        if (cpuid->nent < 1)
                return -E2BIG;
        if (cpuid->nent > KVM_MAX_CPUID_ENTRIES)
                cpuid->nent = KVM_MAX_CPUID_ENTRIES;

        if (sanity_check_entries(entries, cpuid->nent, type))
                return -EINVAL;

        array.entries = kvcalloc(cpuid->nent, sizeof(struct kvm_cpuid_entry2), GFP_KERNEL);
        if (!array.entries)
                return -ENOMEM;

        array.maxnent = cpuid->nent;

        for (i = 0; i < ARRAY_SIZE(funcs); i++) {
                r = get_cpuid_func(&array, funcs[i], type);
                if (r)
                        goto out_free;
        }
        cpuid->nent = array.nent;

        if (copy_to_user(entries, array.entries,
                         array.nent * sizeof(struct kvm_cpuid_entry2)))
                r = -EFAULT;

out_free:
        kvfree(array.entries);
        return r;
}

struct kvm_cpuid_entry2 *kvm_find_cpuid_entry_index(struct kvm_vcpu *vcpu,
                                                    u32 function, u32 index)
{
        return cpuid_entry2_find(vcpu->arch.cpuid_entries, vcpu->arch.cpuid_nent,
                                 function, index);
}
EXPORT_SYMBOL_GPL(kvm_find_cpuid_entry_index);

struct kvm_cpuid_entry2 *kvm_find_cpuid_entry(struct kvm_vcpu *vcpu,
                                              u32 function)
{
        return cpuid_entry2_find(vcpu->arch.cpuid_entries, vcpu->arch.cpuid_nent,
                                 function, KVM_CPUID_INDEX_NOT_SIGNIFICANT);
}
EXPORT_SYMBOL_GPL(kvm_find_cpuid_entry);

/*
 * Intel CPUID semantics treats any query for an out-of-range leaf as if the
 * highest basic leaf (i.e. CPUID.0H:EAX) were requested.  AMD CPUID semantics
 * returns all zeroes for any undefined leaf, whether or not the leaf is in
 * range.  Centaur/VIA follows Intel semantics.
 *
 * A leaf is considered out-of-range if its function is higher than the maximum
 * supported leaf of its associated class or if its associated class does not
 * exist.
 *
 * There are three primary classes to be considered, with their respective
 * ranges described as "<base> - <top>[,<base2> - <top2>] inclusive.  A primary
 * class exists if a guest CPUID entry for its <base> leaf exists.  For a given
 * class, CPUID.<base>.EAX contains the max supported leaf for the class.
 *
 *  - Basic:      0x00000000 - 0x3fffffff, 0x50000000 - 0x7fffffff
 *  - Hypervisor: 0x40000000 - 0x4fffffff
 *  - Extended:   0x80000000 - 0xbfffffff
 *  - Centaur:    0xc0000000 - 0xcfffffff
 *
 * The Hypervisor class is further subdivided into sub-classes that each act as
 * their own independent class associated with a 0x100 byte range.  E.g. if Qemu
 * is advertising support for both HyperV and KVM, the resulting Hypervisor
 * CPUID sub-classes are:
 *
 *  - HyperV:     0x40000000 - 0x400000ff
 *  - KVM:        0x40000100 - 0x400001ff
 */
static struct kvm_cpuid_entry2 *
get_out_of_range_cpuid_entry(struct kvm_vcpu *vcpu, u32 *fn_ptr, u32 index)
{
        struct kvm_cpuid_entry2 *basic, *class;
        u32 function = *fn_ptr;

        basic = kvm_find_cpuid_entry(vcpu, 0);
        if (!basic)
                return NULL;

        if (is_guest_vendor_amd(basic->ebx, basic->ecx, basic->edx) ||
            is_guest_vendor_hygon(basic->ebx, basic->ecx, basic->edx))
                return NULL;

        if (function >= 0x40000000 && function <= 0x4fffffff)
                class = kvm_find_cpuid_entry(vcpu, function & 0xffffff00);
        else if (function >= 0xc0000000)
                class = kvm_find_cpuid_entry(vcpu, 0xc0000000);
        else
                class = kvm_find_cpuid_entry(vcpu, function & 0x80000000);

        if (class && function <= class->eax)
                return NULL;

        /*
         * Leaf specific adjustments are also applied when redirecting to the
         * max basic entry, e.g. if the max basic leaf is 0xb but there is no
         * entry for CPUID.0xb.index (see below), then the output value for EDX
         * needs to be pulled from CPUID.0xb.1.
         */
        *fn_ptr = basic->eax;

        /*
         * The class does not exist or the requested function is out of range;
         * the effective CPUID entry is the max basic leaf.  Note, the index of
         * the original requested leaf is observed!
         */
        return kvm_find_cpuid_entry_index(vcpu, basic->eax, index);
}

bool kvm_cpuid(struct kvm_vcpu *vcpu, u32 *eax, u32 *ebx,
               u32 *ecx, u32 *edx, bool exact_only)
{
        u32 orig_function = *eax, function = *eax, index = *ecx;
        struct kvm_cpuid_entry2 *entry;
        bool exact, used_max_basic = false;

        entry = kvm_find_cpuid_entry_index(vcpu, function, index);
        exact = !!entry;

        if (!entry && !exact_only) {
                entry = get_out_of_range_cpuid_entry(vcpu, &function, index);
                used_max_basic = !!entry;
        }

        if (entry) {
                *eax = entry->eax;
                *ebx = entry->ebx;
                *ecx = entry->ecx;
                *edx = entry->edx;
                if (function == 7 && index == 0) {
                        u64 data;
                        if (!__kvm_get_msr(vcpu, MSR_IA32_TSX_CTRL, &data, true) &&
                            (data & TSX_CTRL_CPUID_CLEAR))
                                *ebx &= ~(F(RTM) | F(HLE));
                }
        } else {
                *eax = *ebx = *ecx = *edx = 0;
                /*
                 * When leaf 0BH or 1FH is defined, CL is pass-through
                 * and EDX is always the x2APIC ID, even for undefined
                 * subleaves. Index 1 will exist iff the leaf is
                 * implemented, so we pass through CL iff leaf 1
                 * exists. EDX can be copied from any existing index.
                 */
                if (function == 0xb || function == 0x1f) {
                        entry = kvm_find_cpuid_entry_index(vcpu, function, 1);
                        if (entry) {
                                *ecx = index & 0xff;
                                *edx = entry->edx;
                        }
                }
        }
        trace_kvm_cpuid(orig_function, index, *eax, *ebx, *ecx, *edx, exact,
                        used_max_basic);
        return exact;
}
EXPORT_SYMBOL_GPL(kvm_cpuid);

int kvm_emulate_cpuid(struct kvm_vcpu *vcpu)
{
        u32 eax, ebx, ecx, edx;

        if (cpuid_fault_enabled(vcpu) && !kvm_require_cpl(vcpu, 0))
                return 1;

        eax = kvm_rax_read(vcpu);
        ecx = kvm_rcx_read(vcpu);
        kvm_cpuid(vcpu, &eax, &ebx, &ecx, &edx, false);
        kvm_rax_write(vcpu, eax);
        kvm_rbx_write(vcpu, ebx);
        kvm_rcx_write(vcpu, ecx);
        kvm_rdx_write(vcpu, edx);
        return kvm_skip_emulated_instruction(vcpu);
}
EXPORT_SYMBOL_GPL(kvm_emulate_cpuid);