/*
 * 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
 *
 * This work is licensed under the terms of the GNU GPL, version 2.  See
 * the COPYING file in the top-level directory.
 *
 */

#include <linux/kvm_host.h>
#include <linux/module.h>
#include <linux/vmalloc.h>
#include <linux/uaccess.h>
#include <asm/user.h>
#include <asm/xsave.h>
#include "cpuid.h"
#include "lapic.h"
#include "mmu.h"
#include "trace.h"

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

        best = kvm_find_cpuid_entry(vcpu, 1, 0);
        if (!best)
                return;

        /* Update OSXSAVE bit */
        if (cpu_has_xsave && best->function == 0x1) {
                best->ecx &= ~(bit(X86_FEATURE_OSXSAVE));
                if (kvm_read_cr4_bits(vcpu, X86_CR4_OSXSAVE))
                        best->ecx |= bit(X86_FEATURE_OSXSAVE);
        }

        if (apic) {
                if (best->ecx & bit(X86_FEATURE_TSC_DEADLINE_TIMER))
                        apic->lapic_timer.timer_mode_mask = 3 << 17;
                else
                        apic->lapic_timer.timer_mode_mask = 1 << 17;
        }

        kvm_pmu_cpuid_update(vcpu);
}

static int is_efer_nx(void)
{
        unsigned long long efer = 0;

        rdmsrl_safe(MSR_EFER, &efer);
        return efer & EFER_NX;
}

static void cpuid_fix_nx_cap(struct kvm_vcpu *vcpu)
{
        int i;
        struct kvm_cpuid_entry2 *e, *entry;

        entry = NULL;
        for (i = 0; i < vcpu->arch.cpuid_nent; ++i) {
                e = &vcpu->arch.cpuid_entries[i];
                if (e->function == 0x80000001) {
                        entry = e;
                        break;
                }
        }
        if (entry && (entry->edx & (1 << 20)) && !is_efer_nx()) {
                entry->edx &= ~(1 << 20);
                printk(KERN_INFO "kvm: guest NX capability removed\n");
        }
}

/* 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 *cpuid_entries;

        r = -E2BIG;
        if (cpuid->nent > KVM_MAX_CPUID_ENTRIES)
                goto out;
        r = -ENOMEM;
        cpuid_entries = vmalloc(sizeof(struct kvm_cpuid_entry) * cpuid->nent);
        if (!cpuid_entries)
                goto out;
        r = -EFAULT;
        if (copy_from_user(cpuid_entries, entries,
                           cpuid->nent * sizeof(struct kvm_cpuid_entry)))
                goto out_free;
        for (i = 0; i < cpuid->nent; i++) {
                vcpu->arch.cpuid_entries[i].function = cpuid_entries[i].function;
                vcpu->arch.cpuid_entries[i].eax = cpuid_entries[i].eax;
                vcpu->arch.cpuid_entries[i].ebx = cpuid_entries[i].ebx;
                vcpu->arch.cpuid_entries[i].ecx = cpuid_entries[i].ecx;
                vcpu->arch.cpuid_entries[i].edx = cpuid_entries[i].edx;
                vcpu->arch.cpuid_entries[i].index = 0;
                vcpu->arch.cpuid_entries[i].flags = 0;
                vcpu->arch.cpuid_entries[i].padding[0] = 0;
                vcpu->arch.cpuid_entries[i].padding[1] = 0;
                vcpu->arch.cpuid_entries[i].padding[2] = 0;
        }
        vcpu->arch.cpuid_nent = cpuid->nent;
        cpuid_fix_nx_cap(vcpu);
        r = 0;
        kvm_apic_set_version(vcpu);
        kvm_x86_ops->cpuid_update(vcpu);
        kvm_update_cpuid(vcpu);

out_free:
        vfree(cpuid_entries);
out:
        return r;
}

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

        r = -E2BIG;
        if (cpuid->nent > KVM_MAX_CPUID_ENTRIES)
                goto out;
        r = -EFAULT;
        if (copy_from_user(&vcpu->arch.cpuid_entries, entries,
                           cpuid->nent * sizeof(struct kvm_cpuid_entry2)))
                goto out;
        vcpu->arch.cpuid_nent = cpuid->nent;
        kvm_apic_set_version(vcpu);
        kvm_x86_ops->cpuid_update(vcpu);
        kvm_update_cpuid(vcpu);
        return 0;

out:
        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;
}

static void cpuid_mask(u32 *word, int wordnum)
{
        *word &= boot_cpu_data.x86_capability[wordnum];
}

static void do_cpuid_1_ent(struct kvm_cpuid_entry2 *entry, u32 function,
                           u32 index)
{
        entry->function = function;
        entry->index = index;
        cpuid_count(entry->function, entry->index,
                    &entry->eax, &entry->ebx, &entry->ecx, &entry->edx);
        entry->flags = 0;
}

static bool supported_xcr0_bit(unsigned bit)
{
        u64 mask = ((u64)1 << bit);

        return mask & (XSTATE_FP | XSTATE_SSE | XSTATE_YMM) & host_xcr0;
}

#define F(x) bit(X86_FEATURE_##x)

static int do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function,
                         u32 index, int *nent, int maxnent)
{
        int r;
        unsigned f_nx = is_efer_nx() ? F(NX) : 0;
#ifdef CONFIG_X86_64
        unsigned f_gbpages = (kvm_x86_ops->get_lpage_level() == PT_PDPE_LEVEL)
                                ? F(GBPAGES) : 0;
        unsigned f_lm = F(LM);
#else
        unsigned f_gbpages = 0;
        unsigned f_lm = 0;
#endif
        unsigned f_rdtscp = kvm_x86_ops->rdtscp_supported() ? F(RDTSCP) : 0;
        unsigned f_invpcid = kvm_x86_ops->invpcid_supported() ? F(INVPCID) : 0;

        /* cpuid 1.edx */
        const u32 kvm_supported_word0_x86_features =
                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(CLFLSH) |
                0 /* Reserved, DS, ACPI */ | F(MMX) |
                F(FXSR) | F(XMM) | F(XMM2) | F(SELFSNOOP) |
                0 /* HTT, TM, Reserved, PBE */;
        /* cpuid 0x80000001.edx */
        const u32 kvm_supported_word1_x86_features =
                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);
        /* cpuid 1.ecx */
        const u32 kvm_supported_word4_x86_features =
                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, 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);
        /* cpuid 0x80000001.ecx */
        const u32 kvm_supported_word6_x86_features =
                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);

        /* cpuid 0xC0000001.edx */
        const u32 kvm_supported_word5_x86_features =
                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);

        /* cpuid 7.0.ebx */
        const u32 kvm_supported_word9_x86_features =
                F(FSGSBASE) | F(BMI1) | F(HLE) | F(AVX2) | F(SMEP) |
                F(BMI2) | F(ERMS) | f_invpcid | F(RTM);

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

        r = -E2BIG;

        if (*nent >= maxnent)
                goto out;

        do_cpuid_1_ent(entry, function, index);
        ++*nent;

        switch (function) {
        case 0:
                entry->eax = min(entry->eax, (u32)0xd);
                break;
        case 1:
                entry->edx &= kvm_supported_word0_x86_features;
                cpuid_mask(&entry->edx, 0);
                entry->ecx &= kvm_supported_word4_x86_features;
                cpuid_mask(&entry->ecx, 4);
                /* we support x2apic emulation even if host does not support
                 * it since we emulate x2apic in software */
                entry->ecx |= F(X2APIC);
                break;
        /* function 2 entries are STATEFUL. That is, repeated cpuid commands
         * may return different values. This forces us to get_cpu() before
         * issuing the first command, and also to emulate this annoying behavior
         * in kvm_emulate_cpuid() using KVM_CPUID_FLAG_STATE_READ_NEXT */
        case 2: {
                int t, times = entry->eax & 0xff;

                entry->flags |= KVM_CPUID_FLAG_STATEFUL_FUNC;
                entry->flags |= KVM_CPUID_FLAG_STATE_READ_NEXT;
                for (t = 1; t < times; ++t) {
                        if (*nent >= maxnent)
                                goto out;

                        do_cpuid_1_ent(&entry[t], function, 0);
                        entry[t].flags |= KVM_CPUID_FLAG_STATEFUL_FUNC;
                        ++*nent;
                }
                break;
        }
        /* function 4 has additional index. */
        case 4: {
                int i, cache_type;

                entry->flags |= KVM_CPUID_FLAG_SIGNIFCANT_INDEX;
                /* read more entries until cache_type is zero */
                for (i = 1; ; ++i) {
                        if (*nent >= maxnent)
                                goto out;

                        cache_type = entry[i - 1].eax & 0x1f;
                        if (!cache_type)
                                break;
                        do_cpuid_1_ent(&entry[i], function, i);
                        entry[i].flags |=
                               KVM_CPUID_FLAG_SIGNIFCANT_INDEX;
                        ++*nent;
                }
                break;
        }
        case 7: {
                entry->flags |= KVM_CPUID_FLAG_SIGNIFCANT_INDEX;
                /* Mask ebx against host capability word 9 */
                if (index == 0) {
                        entry->ebx &= kvm_supported_word9_x86_features;
                        cpuid_mask(&entry->ebx, 9);
                        // TSC_ADJUST is emulated
                        entry->ebx |= F(TSC_ADJUST);
                } else
                        entry->ebx = 0;
                entry->eax = 0;
                entry->ecx = 0;
                entry->edx = 0;
                break;
        }
        case 9:
                break;
        case 0xa: { /* Architectural Performance Monitoring */
                struct x86_pmu_capability cap;
                union cpuid10_eax eax;
                union cpuid10_edx edx;

                perf_get_x86_pmu_capability(&cap);

                /*
                 * Only support guest architectural pmu on a host
                 * with architectural pmu.
                 */
                if (!cap.version)
                        memset(&cap, 0, sizeof(cap));

                eax.split.version_id = min(cap.version, 2);
                eax.split.num_counters = cap.num_counters_gp;
                eax.split.bit_width = cap.bit_width_gp;
                eax.split.mask_length = cap.events_mask_len;

                edx.split.num_counters_fixed = cap.num_counters_fixed;
                edx.split.bit_width_fixed = cap.bit_width_fixed;
                edx.split.reserved = 0;

                entry->eax = eax.full;
                entry->ebx = cap.events_mask;
                entry->ecx = 0;
                entry->edx = edx.full;
                break;
        }
        /* function 0xb has additional index. */
        case 0xb: {
                int i, level_type;

                entry->flags |= KVM_CPUID_FLAG_SIGNIFCANT_INDEX;
                /* read more entries until level_type is zero */
                for (i = 1; ; ++i) {
                        if (*nent >= maxnent)
                                goto out;

                        level_type = entry[i - 1].ecx & 0xff00;
                        if (!level_type)
                                break;
                        do_cpuid_1_ent(&entry[i], function, i);
                        entry[i].flags |=
                               KVM_CPUID_FLAG_SIGNIFCANT_INDEX;
                        ++*nent;
                }
                break;
        }
        case 0xd: {
                int idx, i;

                entry->flags |= KVM_CPUID_FLAG_SIGNIFCANT_INDEX;
                for (idx = 1, i = 1; idx < 64; ++idx) {
                        if (*nent >= maxnent)
                                goto out;

                        do_cpuid_1_ent(&entry[i], function, idx);
                        if (entry[i].eax == 0 || !supported_xcr0_bit(idx))
                                continue;
                        entry[i].flags |=
                               KVM_CPUID_FLAG_SIGNIFCANT_INDEX;
                        ++*nent;
                        ++i;
                }
                break;
        }
        case KVM_CPUID_SIGNATURE: {
                static const char signature[12] = "KVMKVMKVM\0\0";
                const u32 *sigptr = (const u32 *)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);

                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, 0x8000001a);
                break;
        case 0x80000001:
                entry->edx &= kvm_supported_word1_x86_features;
                cpuid_mask(&entry->edx, 1);
                entry->ecx &= kvm_supported_word6_x86_features;
                cpuid_mask(&entry->ecx, 6);
                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 (!g_phys_as)
                        g_phys_as = phys_as;
                entry->eax = g_phys_as | (virt_as << 8);
                entry->ebx = entry->edx = 0;
                break;
        }
        case 0x80000019:
                entry->ecx = entry->edx = 0;
                break;
        case 0x8000001a:
                break;
        case 0x8000001d:
                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:
                entry->edx &= kvm_supported_word5_x86_features;
                cpuid_mask(&entry->edx, 5);
                break;
        case 3: /* Processor serial number */
        case 5: /* MONITOR/MWAIT */
        case 6: /* Thermal management */
        case 0x80000007: /* Advanced power management */
        case 0xC0000002:
        case 0xC0000003:
        case 0xC0000004:
        default:
                entry->eax = entry->ebx = entry->ecx = entry->edx = 0;
                break;
        }

        kvm_x86_ops->set_supported_cpuid(function, entry);

        r = 0;

out:
        put_cpu();

        return r;
}

#undef F

struct kvm_cpuid_param {
        u32 func;
        u32 idx;
        bool has_leaf_count;
        bool (*qualifier)(const struct kvm_cpuid_param *param);
};

static bool is_centaur_cpu(const struct kvm_cpuid_param *param)
{
        return boot_cpu_data.x86_vendor == X86_VENDOR_CENTAUR;
}

int kvm_dev_ioctl_get_supported_cpuid(struct kvm_cpuid2 *cpuid,
                                      struct kvm_cpuid_entry2 __user *entries)
{
        struct kvm_cpuid_entry2 *cpuid_entries;
        int limit, nent = 0, r = -E2BIG, i;
        u32 func;
        static const struct kvm_cpuid_param param[] = {
                { .func = 0, .has_leaf_count = true },
                { .func = 0x80000000, .has_leaf_count = true },
                { .func = 0xC0000000, .qualifier = is_centaur_cpu, .has_leaf_count = true },
                { .func = KVM_CPUID_SIGNATURE },
                { .func = KVM_CPUID_FEATURES },
        };

        if (cpuid->nent < 1)
                goto out;
        if (cpuid->nent > KVM_MAX_CPUID_ENTRIES)
                cpuid->nent = KVM_MAX_CPUID_ENTRIES;
        r = -ENOMEM;
        cpuid_entries = vmalloc(sizeof(struct kvm_cpuid_entry2) * cpuid->nent);
        if (!cpuid_entries)
                goto out;

        r = 0;
        for (i = 0; i < ARRAY_SIZE(param); i++) {
                const struct kvm_cpuid_param *ent = &param[i];

                if (ent->qualifier && !ent->qualifier(ent))
                        continue;

                r = do_cpuid_ent(&cpuid_entries[nent], ent->func, ent->idx,
                                &nent, cpuid->nent);

                if (r)
                        goto out_free;

                if (!ent->has_leaf_count)
                        continue;

                limit = cpuid_entries[nent - 1].eax;
                for (func = ent->func + 1; func <= limit && nent < cpuid->nent && r == 0; ++func)
                        r = do_cpuid_ent(&cpuid_entries[nent], func, ent->idx,
                                     &nent, cpuid->nent);

                if (r)
                        goto out_free;
        }

        r = -EFAULT;
        if (copy_to_user(entries, cpuid_entries,
                         nent * sizeof(struct kvm_cpuid_entry2)))
                goto out_free;
        cpuid->nent = nent;
        r = 0;

out_free:
        vfree(cpuid_entries);
out:
        return r;
}

static int move_to_next_stateful_cpuid_entry(struct kvm_vcpu *vcpu, int i)
{
        struct kvm_cpuid_entry2 *e = &vcpu->arch.cpuid_entries[i];
        int j, nent = vcpu->arch.cpuid_nent;

        e->flags &= ~KVM_CPUID_FLAG_STATE_READ_NEXT;
        /* when no next entry is found, the current entry[i] is reselected */
        for (j = i + 1; ; j = (j + 1) % nent) {
                struct kvm_cpuid_entry2 *ej = &vcpu->arch.cpuid_entries[j];
                if (ej->function == e->function) {
                        ej->flags |= KVM_CPUID_FLAG_STATE_READ_NEXT;
                        return j;
                }
        }
        return 0; /* silence gcc, even though control never reaches here */
}

/* find an entry with matching function, matching index (if needed), and that
 * should be read next (if it's stateful) */
static int is_matching_cpuid_entry(struct kvm_cpuid_entry2 *e,
        u32 function, u32 index)
{
        if (e->function != function)
                return 0;
        if ((e->flags & KVM_CPUID_FLAG_SIGNIFCANT_INDEX) && e->index != index)
                return 0;
        if ((e->flags & KVM_CPUID_FLAG_STATEFUL_FUNC) &&
            !(e->flags & KVM_CPUID_FLAG_STATE_READ_NEXT))
                return 0;
        return 1;
}

struct kvm_cpuid_entry2 *kvm_find_cpuid_entry(struct kvm_vcpu *vcpu,
                                              u32 function, u32 index)
{
        int i;
        struct kvm_cpuid_entry2 *best = NULL;

        for (i = 0; i < vcpu->arch.cpuid_nent; ++i) {
                struct kvm_cpuid_entry2 *e;

                e = &vcpu->arch.cpuid_entries[i];
                if (is_matching_cpuid_entry(e, function, index)) {
                        if (e->flags & KVM_CPUID_FLAG_STATEFUL_FUNC)
                                move_to_next_stateful_cpuid_entry(vcpu, i);
                        best = e;
                        break;
                }
        }
        return best;
}
EXPORT_SYMBOL_GPL(kvm_find_cpuid_entry);

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

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

/*
 * If no match is found, check whether we exceed the vCPU's limit
 * and return the content of the highest valid _standard_ leaf instead.
 * This is to satisfy the CPUID specification.
 */
static struct kvm_cpuid_entry2* check_cpuid_limit(struct kvm_vcpu *vcpu,
                                                  u32 function, u32 index)
{
        struct kvm_cpuid_entry2 *maxlevel;

        maxlevel = kvm_find_cpuid_entry(vcpu, function & 0x80000000, 0);
        if (!maxlevel || maxlevel->eax >= function)
                return NULL;
        if (function & 0x80000000) {
                maxlevel = kvm_find_cpuid_entry(vcpu, 0, 0);
                if (!maxlevel)
                        return NULL;
        }
        return kvm_find_cpuid_entry(vcpu, maxlevel->eax, index);
}

void kvm_cpuid(struct kvm_vcpu *vcpu, u32 *eax, u32 *ebx, u32 *ecx, u32 *edx)
{
        u32 function = *eax, index = *ecx;
        struct kvm_cpuid_entry2 *best;

        best = kvm_find_cpuid_entry(vcpu, function, index);

        if (!best)
                best = check_cpuid_limit(vcpu, function, index);

        if (best) {
                *eax = best->eax;
                *ebx = best->ebx;
                *ecx = best->ecx;
                *edx = best->edx;
        } else
                *eax = *ebx = *ecx = *edx = 0;
}
EXPORT_SYMBOL_GPL(kvm_cpuid);

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

        function = eax = kvm_register_read(vcpu, VCPU_REGS_RAX);
        ecx = kvm_register_read(vcpu, VCPU_REGS_RCX);
        kvm_cpuid(vcpu, &eax, &ebx, &ecx, &edx);
        kvm_register_write(vcpu, VCPU_REGS_RAX, eax);
        kvm_register_write(vcpu, VCPU_REGS_RBX, ebx);
        kvm_register_write(vcpu, VCPU_REGS_RCX, ecx);
        kvm_register_write(vcpu, VCPU_REGS_RDX, edx);
        kvm_x86_ops->skip_emulated_instruction(vcpu);
        trace_kvm_cpuid(function, eax, ebx, ecx, edx);
}
EXPORT_SYMBOL_GPL(kvm_emulate_cpuid);