kvm: x86: Add ability to skip TLB flush when switching CR3

Remove the implicit flush from the set_cr3 handlers, so that the
callers are able to decide whether to flush the TLB or not.
Signed-off-by: Junaid Shahid <junaids@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/mmu.c

@@ -4070,6 +4070,7 @@ static bool fast_cr3_switch(struct kvm_vcpu *vcpu, gpa_t new_cr3,
 
 			kvm_make_request(KVM_REQ_LOAD_CR3, vcpu);
 			kvm_make_request(KVM_REQ_MMU_SYNC, vcpu);
+			kvm_x86_ops->tlb_flush(vcpu, true);
 			__clear_sp_write_flooding_count(
 				page_header(mmu->root_hpa));
 
@@ -4851,6 +4852,7 @@ int kvm_mmu_load(struct kvm_vcpu *vcpu)
 	if (r)
 		goto out;
 	kvm_mmu_load_cr3(vcpu);
+	kvm_x86_ops->tlb_flush(vcpu, true);
 out:
 	return r;
 }

arch/x86/kvm/mmu.h

@@ -88,7 +88,6 @@ static inline int kvm_mmu_reload(struct kvm_vcpu *vcpu)
 
 static inline void kvm_mmu_load_cr3(struct kvm_vcpu *vcpu)
 {
-	/* set_cr3() should ensure TLB has been flushed */
 	if (VALID_PAGE(vcpu->arch.mmu.root_hpa))
 		vcpu->arch.mmu.set_cr3(vcpu, vcpu->arch.mmu.root_hpa);
 }

arch/x86/kvm/svm.c

@@ -2884,7 +2884,6 @@ static void nested_svm_set_tdp_cr3(struct kvm_vcpu *vcpu,
 
 	svm->vmcb->control.nested_cr3 = __sme_set(root);
 	mark_dirty(svm->vmcb, VMCB_NPT);
-	svm_flush_tlb(vcpu, true);
 }
 
 static void nested_svm_inject_npf_exit(struct kvm_vcpu *vcpu,
@@ -5766,7 +5765,6 @@ static void svm_set_cr3(struct kvm_vcpu *vcpu, unsigned long root)
 
 	svm->vmcb->save.cr3 = __sme_set(root);
 	mark_dirty(svm->vmcb, VMCB_CR);
-	svm_flush_tlb(vcpu, true);
 }
 
 static void set_tdp_cr3(struct kvm_vcpu *vcpu, unsigned long root)
@@ -5779,8 +5777,6 @@ static void set_tdp_cr3(struct kvm_vcpu *vcpu, unsigned long root)
 	/* Also sync guest cr3 here in case we live migrate */
 	svm->vmcb->save.cr3 = kvm_read_cr3(vcpu);
 	mark_dirty(svm->vmcb, VMCB_CR);
-
-	svm_flush_tlb(vcpu, true);
 }
 
 static int is_disabled(void)

arch/x86/kvm/vmx.c

@@ -5029,7 +5029,6 @@ static void vmx_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3)
 		ept_load_pdptrs(vcpu);
 	}
 
-	vmx_flush_tlb(vcpu, true);
 	vmcs_writel(GUEST_CR3, guest_cr3);
 }