KVM: x86: Introduce helper to handle Hyper-V paravirt TLB flush requests

As a preparation to making Hyper-V emulation optional, introduce a helper
to handle pending KVM_REQ_HV_TLB_FLUSH requests.

No functional change intended.

Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Tested-by: Jeremi Piotrowski <jpiotrowski@linux.microsoft.com>
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Link: https://lore.kernel.org/r/20231205103630.1391318-8-vkuznets@redhat.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

Author: vittyvk

arch/x86/kvm/hyperv.h

@@ -247,6 +247,19 @@ static inline int kvm_hv_verify_vp_assist(struct kvm_vcpu *vcpu)
 	return kvm_hv_get_assist_page(vcpu);
 }
 
+static inline void kvm_hv_nested_transtion_tlb_flush(struct kvm_vcpu *vcpu,
+						     bool tdp_enabled)
+{
+	/*
+	 * KVM_REQ_HV_TLB_FLUSH flushes entries from either L1's VP_ID or
+	 * L2's VP_ID upon request from the guest. Make sure we check for
+	 * pending entries in the right FIFO upon L1/L2 transition as these
+	 * requests are put by other vCPUs asynchronously.
+	 */
+	if (to_hv_vcpu(vcpu) && tdp_enabled)
+		kvm_make_request(KVM_REQ_HV_TLB_FLUSH, vcpu);
+}
+
 int kvm_hv_vcpu_flush_tlb(struct kvm_vcpu *vcpu);
 
 #endif

arch/x86/kvm/svm/nested.c

@@ -487,14 +487,8 @@ static void nested_save_pending_event_to_vmcb12(struct vcpu_svm *svm,
 
 static void nested_svm_transition_tlb_flush(struct kvm_vcpu *vcpu)
 {
-	/*
-	 * KVM_REQ_HV_TLB_FLUSH flushes entries from either L1's VP_ID or
-	 * L2's VP_ID upon request from the guest. Make sure we check for
-	 * pending entries in the right FIFO upon L1/L2 transition as these
-	 * requests are put by other vCPUs asynchronously.
-	 */
-	if (to_hv_vcpu(vcpu) && npt_enabled)
-		kvm_make_request(KVM_REQ_HV_TLB_FLUSH, vcpu);
+	/* Handle pending Hyper-V TLB flush requests */
+	kvm_hv_nested_transtion_tlb_flush(vcpu, npt_enabled);
 
 	/*
 	 * TODO: optimize unconditional TLB flush/MMU sync.  A partial list of

arch/x86/kvm/vmx/nested.c

@@ -1139,14 +1139,8 @@ static void nested_vmx_transition_tlb_flush(struct kvm_vcpu *vcpu,
 {
 	struct vcpu_vmx *vmx = to_vmx(vcpu);
 
-	/*
-	 * KVM_REQ_HV_TLB_FLUSH flushes entries from either L1's VP_ID or
-	 * L2's VP_ID upon request from the guest. Make sure we check for
-	 * pending entries in the right FIFO upon L1/L2 transition as these
-	 * requests are put by other vCPUs asynchronously.
-	 */
-	if (to_hv_vcpu(vcpu) && enable_ept)
-		kvm_make_request(KVM_REQ_HV_TLB_FLUSH, vcpu);
+	/* Handle pending Hyper-V TLB flush requests */
+	kvm_hv_nested_transtion_tlb_flush(vcpu, enable_ept);
 
 	/*
 	 * If vmcs12 doesn't use VPID, L1 expects linear and combined mappings