Commit 3be29eb7 authored by Sean Christopherson's avatar Sean Christopherson Committed by Paolo Bonzini
Browse files

KVM: x86: Report error when setting CPUID if Hyper-V allocation fails 



Return -ENOMEM back to userspace if allocating the Hyper-V vCPU struct
fails when enabling Hyper-V in guest CPUID.  Silently ignoring failure
means that KVM will not have an up-to-date CPUID cache if allocating the
struct succeeds later on, e.g. when activating SynIC.

Rejecting the CPUID operation also guarantess that vcpu->arch.hyperv is
non-NULL if hyperv_enabled is true, which will allow for additional
cleanup, e.g. in the eVMCS code.

Note, the initialization needs to be done before CPUID is set, and more
subtly before kvm_check_cpuid(), which potentially enables dynamic
XFEATURES.  Sadly, there's no easy way to avoid exposing Hyper-V details
to CPUID or vice versa.  Expose kvm_hv_vcpu_init() and the Hyper-V CPUID
signature to CPUID instead of exposing cpuid_entry2_find() outside of
CPUID code.  It's hard to envision kvm_hv_vcpu_init() being misused,
whereas cpuid_entry2_find() absolutely shouldn't be used outside of core
CPUID code.

Fixes: 10d7bf1e ("KVM: x86: hyper-v: Cache guest CPUID leaves determining features availability")
Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
Signed-off-by: default avatarVitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
Link: https://lore.kernel.org/r/20220830133737.1539624-6-vkuznets@redhat.com


Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 1cac8d9f

arch/x86/kvm/cpuid.c

+17 −1
Original line number Diff line number Diff line
@@ -311,6 +311,15 @@ void kvm_update_cpuid_runtime(struct kvm_vcpu *vcpu) 
}

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;
@@ -341,7 +350,8 @@ static void kvm_vcpu_after_set_cpuid(struct kvm_vcpu *vcpu) 
	vcpu->arch.cr4_guest_rsvd_bits =

	    __cr4_reserved_bits(guest_cpuid_has, vcpu);



	kvm_hv_set_cpuid(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);
@@ -404,6 +414,12 @@ static int kvm_set_cpuid(struct kvm_vcpu *vcpu, struct kvm_cpuid_entry2 *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;

arch/x86/kvm/hyperv.c

+14 −16
Original line number Diff line number Diff line
@@ -38,9 +38,6 @@ 
#include "irq.h"

#include "fpu.h"



/* "Hv#1" signature */

#define HYPERV_CPUID_SIGNATURE_EAX 0x31237648



#define KVM_HV_MAX_SPARSE_VCPU_SET_BITS DIV_ROUND_UP(KVM_MAX_VCPUS, 64)



static void stimer_mark_pending(struct kvm_vcpu_hv_stimer *stimer,
@@ -934,7 +931,7 @@ static void stimer_init(struct kvm_vcpu_hv_stimer *stimer, int timer_index) 
	stimer_prepare_msg(stimer);

}



static int kvm_hv_vcpu_init(struct kvm_vcpu *vcpu)

int kvm_hv_vcpu_init(struct kvm_vcpu *vcpu)

{

	struct kvm_vcpu_hv *hv_vcpu = to_hv_vcpu(vcpu);

	int i;
@@ -1984,26 +1981,27 @@ static u64 kvm_hv_send_ipi(struct kvm_vcpu *vcpu, struct kvm_hv_hcall *hc) 
	return HV_STATUS_SUCCESS;

}



void kvm_hv_set_cpuid(struct kvm_vcpu *vcpu)

void kvm_hv_set_cpuid(struct kvm_vcpu *vcpu, bool hyperv_enabled)

{

	struct kvm_vcpu_hv *hv_vcpu = to_hv_vcpu(vcpu);

	struct kvm_cpuid_entry2 *entry;

	struct kvm_vcpu_hv *hv_vcpu;



	entry = kvm_find_cpuid_entry(vcpu, HYPERV_CPUID_INTERFACE);

	if (entry && entry->eax == HYPERV_CPUID_SIGNATURE_EAX) {

		vcpu->arch.hyperv_enabled = true;

	} else {

		vcpu->arch.hyperv_enabled = false;

		return;

	}

	vcpu->arch.hyperv_enabled = hyperv_enabled;



	if (kvm_hv_vcpu_init(vcpu))

	if (!hv_vcpu) {

		/*

		 * KVM should have already allocated kvm_vcpu_hv if Hyper-V is

		 * enabled in CPUID.

		 */

		WARN_ON_ONCE(vcpu->arch.hyperv_enabled);

		return;



	hv_vcpu = to_hv_vcpu(vcpu);

	}



	memset(&hv_vcpu->cpuid_cache, 0, sizeof(hv_vcpu->cpuid_cache));



	if (!vcpu->arch.hyperv_enabled)

		return;



	entry = kvm_find_cpuid_entry(vcpu, HYPERV_CPUID_FEATURES);

	if (entry) {

		hv_vcpu->cpuid_cache.features_eax = entry->eax;

arch/x86/kvm/hyperv.h

+5 −1
Original line number Diff line number Diff line
@@ -23,6 +23,9 @@ 


#include <linux/kvm_host.h>



/* "Hv#1" signature */

#define HYPERV_CPUID_SIGNATURE_EAX 0x31237648



/*

 * The #defines related to the synthetic debugger are required by KDNet, but

 * they are not documented in the Hyper-V TLFS because the synthetic debugger
@@ -141,7 +144,8 @@ void kvm_hv_request_tsc_page_update(struct kvm *kvm); 


void kvm_hv_init_vm(struct kvm *kvm);

void kvm_hv_destroy_vm(struct kvm *kvm);

void kvm_hv_set_cpuid(struct kvm_vcpu *vcpu);

int kvm_hv_vcpu_init(struct kvm_vcpu *vcpu);

void kvm_hv_set_cpuid(struct kvm_vcpu *vcpu, bool hyperv_enabled);

int kvm_hv_set_enforce_cpuid(struct kvm_vcpu *vcpu, bool enforce);

int kvm_vm_ioctl_hv_eventfd(struct kvm *kvm, struct kvm_hyperv_eventfd *args);

int kvm_get_hv_cpuid(struct kvm_vcpu *vcpu, struct kvm_cpuid2 *cpuid,