diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index f5bf654f025e..bc14c3d0c0cc 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -1757,11 +1757,16 @@ struct kvm_hv_hcall {
 static u64 kvm_get_sparse_vp_set(struct kvm *kvm, struct kvm_hv_hcall *hc,
 				 u64 *sparse_banks, gpa_t offset)
 {
+	u16 var_cnt;
+
 	if (hc->var_cnt > 64)
 		return -EINVAL;
 
+	/* Ignore banks that cannot possibly contain a legal VP index. */
+	var_cnt = min_t(u16, hc->var_cnt, KVM_HV_MAX_SPARSE_VCPU_SET_BITS);
+
 	return kvm_read_guest(kvm, hc->ingpa + offset, sparse_banks,
-			      hc->var_cnt * sizeof(*sparse_banks));
+			      var_cnt * sizeof(*sparse_banks));
 }
 
 static u64 kvm_hv_flush_tlb(struct kvm_vcpu *vcpu, struct kvm_hv_hcall *hc, bool ex)
@@ -1774,9 +1779,17 @@ static u64 kvm_hv_flush_tlb(struct kvm_vcpu *vcpu, struct kvm_hv_hcall *hc, bool
 	DECLARE_BITMAP(vcpu_bitmap, KVM_MAX_VCPUS);
 	unsigned long *vcpu_mask;
 	u64 valid_bank_mask;
-	u64 sparse_banks[64];
+	u64 sparse_banks[KVM_HV_MAX_SPARSE_VCPU_SET_BITS];
 	bool all_cpus;
 
+	/*
+	 * The Hyper-V TLFS doesn't allow more than 64 sparse banks, e.g. the
+	 * valid mask is a u64.  Fail the build if KVM's max allowed number of
+	 * vCPUs (>4096) would exceed this limit, KVM will additional changes
+	 * for Hyper-V support to avoid setting the guest up to fail.
+	 */
+	BUILD_BUG_ON(KVM_HV_MAX_SPARSE_VCPU_SET_BITS > 64);
+
 	if (!ex) {
 		if (hc->fast) {
 			flush.address_space = hc->ingpa;
@@ -1898,7 +1911,7 @@ static u64 kvm_hv_send_ipi(struct kvm_vcpu *vcpu, struct kvm_hv_hcall *hc, bool
 	DECLARE_BITMAP(vcpu_bitmap, KVM_MAX_VCPUS);
 	unsigned long *vcpu_mask;
 	unsigned long valid_bank_mask;
-	u64 sparse_banks[64];
+	u64 sparse_banks[KVM_HV_MAX_SPARSE_VCPU_SET_BITS];
 	u32 vector;
 	bool all_cpus;