Commit 43561123 authored by Jim Mattson's avatar Jim Mattson Committed by Paolo Bonzini
Browse files

kvm: x86: Improve emulation of CPUID leaves 0BH and 1FH 



For these CPUID leaves, the EDX output is not dependent on the ECX
input (i.e. the SIGNIFCANT_INDEX flag doesn't apply to
EDX). Furthermore, the low byte of the ECX output is always identical
to the low byte of the ECX input. KVM does not produce the correct ECX
and EDX outputs for any undefined subleaves beyond the first.

Special-case these CPUID leaves in kvm_cpuid, so that the ECX and EDX
outputs are properly generated for all undefined subleaves.

Fixes: 07716717 ("KVM: Enhance guest cpuid management")
Fixes: a87f2d3a ("KVM: x86: Add Intel CPUID.1F cpuid emulation support")
Signed-off-by: default avatarJim Mattson <jmattson@google.com>
Reviewed-by: default avatarMarc Orr <marcorr@google.com>
Reviewed-by: default avatarPeter Shier <pshier@google.com>
Reviewed-by: default avatarJacob Xu <jacobhxu@google.com>
Cc: Sean Christopherson <sean.j.christopherson@intel.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 3ca94192

arch/x86/kvm/cpuid.c

+47 −36
Original line number Diff line number Diff line
@@ -973,53 +973,64 @@ struct kvm_cpuid_entry2 *kvm_find_cpuid_entry(struct kvm_vcpu *vcpu, 
EXPORT_SYMBOL_GPL(kvm_find_cpuid_entry);



/*

 * 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.

 * If the basic or extended CPUID leaf requested is higher than the

 * maximum supported basic or extended leaf, respectively, then it is

 * out of range.

 */

static struct kvm_cpuid_entry2* check_cpuid_limit(struct kvm_vcpu *vcpu,

                                                  u32 function, u32 index)

static bool cpuid_function_in_range(struct kvm_vcpu *vcpu, u32 function)

{

	struct kvm_cpuid_entry2 *maxlevel;

	struct kvm_cpuid_entry2 *max;



	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);

	max = kvm_find_cpuid_entry(vcpu, function & 0x80000000, 0);

	return max && function <= max->eax;

}



bool kvm_cpuid(struct kvm_vcpu *vcpu, u32 *eax, u32 *ebx,

	       u32 *ecx, u32 *edx, bool check_limit)

{

	u32 function = *eax, index = *ecx;

	struct kvm_cpuid_entry2 *best;

	bool entry_found = true;



	best = kvm_find_cpuid_entry(vcpu, function, index);



	if (!best) {

		entry_found = false;

		if (!check_limit)

			goto out;

	struct kvm_cpuid_entry2 *entry;

	struct kvm_cpuid_entry2 *max;

	bool found;



		best = check_cpuid_limit(vcpu, function, index);

	}



out:

	if (best) {

		*eax = best->eax;

		*ebx = best->ebx;

		*ecx = best->ecx;

		*edx = best->edx;

	} else

	entry = kvm_find_cpuid_entry(vcpu, function, index);

	found = 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.

	 */

	if (!entry && check_limit && !cpuid_function_in_range(vcpu, function)) {

		max = kvm_find_cpuid_entry(vcpu, 0, 0);

		if (max) {

			function = max->eax;

			entry = kvm_find_cpuid_entry(vcpu, function, index);

		}

	}

	if (entry) {

		*eax = entry->eax;

		*ebx = entry->ebx;

		*ecx = entry->ecx;

		*edx = entry->edx;

	} else {

		*eax = *ebx = *ecx = *edx = 0;

	trace_kvm_cpuid(function, *eax, *ebx, *ecx, *edx, entry_found);

	return entry_found;

		/*

		 * 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(vcpu, function, 1);

			if (entry) {

				*ecx = index & 0xff;

				*edx = entry->edx;

			}

		}

	}

	trace_kvm_cpuid(function, *eax, *ebx, *ecx, *edx, found);

	return found;

}

EXPORT_SYMBOL_GPL(kvm_cpuid);

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