1 files changed, 670 insertions, 0 deletions

diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
new file mode 100644
index 000000000000..89b02bfaaca5
--- /dev/null
+++ b/arch/x86/kvm/cpuid.c
@@ -0,0 +1,670 @@
+/*
+ * 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) | 0 /* 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(AVX2) | F(SMEP) | F(BMI2) | F(ERMS);
+
+	/* 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 = 0;
+		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_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_emulate_cpuid(struct kvm_vcpu *vcpu)
+{
+	u32 function, index;
+	struct kvm_cpuid_entry2 *best;
+
+	function = kvm_register_read(vcpu, VCPU_REGS_RAX);
+	index = kvm_register_read(vcpu, VCPU_REGS_RCX);
+	kvm_register_write(vcpu, VCPU_REGS_RAX, 0);
+	kvm_register_write(vcpu, VCPU_REGS_RBX, 0);
+	kvm_register_write(vcpu, VCPU_REGS_RCX, 0);
+	kvm_register_write(vcpu, VCPU_REGS_RDX, 0);
+	best = kvm_find_cpuid_entry(vcpu, function, index);
+
+	if (!best)
+		best = check_cpuid_limit(vcpu, function, index);
+
+	if (best) {
+		kvm_register_write(vcpu, VCPU_REGS_RAX, best->eax);
+		kvm_register_write(vcpu, VCPU_REGS_RBX, best->ebx);
+		kvm_register_write(vcpu, VCPU_REGS_RCX, best->ecx);
+		kvm_register_write(vcpu, VCPU_REGS_RDX, best->edx);
+	}
+	kvm_x86_ops->skip_emulated_instruction(vcpu);
+	trace_kvm_cpuid(function,
+			kvm_register_read(vcpu, VCPU_REGS_RAX),
+			kvm_register_read(vcpu, VCPU_REGS_RBX),
+			kvm_register_read(vcpu, VCPU_REGS_RCX),
+			kvm_register_read(vcpu, VCPU_REGS_RDX));
+}
+EXPORT_SYMBOL_GPL(kvm_emulate_cpuid);