arch/x86/kvm/cpuid.c - kernel/msm-4.19 - Gitiles

 /*
  * 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;

 	/* 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 */ |
 		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(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 capbability word 9 */
 		if (index == 0) {
 			entry->ebx &= kvm_supported_word9_x86_features;
 			cpuid_mask(&entry->ebx, 9);
 		} 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: {
 		char signature[12] = "KVMKVMKVM\0\0";
 		u32 *sigptr = (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)(struct kvm_cpuid_param *param);
 };

 static bool is_centaur_cpu(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 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++) {
 		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;
 }

 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);
	/*
	* 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;

	/* 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 */ \|
	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(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 capbability word 9 */
	if (index == 0) {
	entry->ebx &= kvm_supported_word9_x86_features;
	cpuid_mask(&entry->ebx, 9);
	} 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: {
	char signature[12] = "KVMKVMKVM\0\0";
	u32 sigptr = (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)(struct kvm_cpuid_param param);
	};

	static bool is_centaur_cpu(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 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++) {
	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;
	}

	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);