KVM: x86: unify callbacks to load paging root

Similar to what kvm-intel.ko is doing, provide a single callback that
merges svm_set_cr3, set_tdp_cr3 and nested_svm_set_tdp_cr3.

This lets us unify the set_cr3 and set_tdp_cr3 entries in kvm_x86_ops.
I'm doing that in this same patch because splitting it adds quite a bit
of churn due to the need for forward declarations.  For the same reason
the assignment to vcpu->arch.mmu->set_cr3 is moved to kvm_init_shadow_mmu
from init_kvm_softmmu and nested_svm_init_mmu_context.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/include/asm/kvm_host.h

@@ -387,7 +387,6 @@ struct kvm_mmu_root_info {
  * current mmu mode.
  */
 struct kvm_mmu {
-	void (*set_cr3)(struct kvm_vcpu *vcpu, unsigned long root);
 	unsigned long (*get_guest_pgd)(struct kvm_vcpu *vcpu);
 	u64 (*get_pdptr)(struct kvm_vcpu *vcpu, int index);
 	int (*page_fault)(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa, u32 err,
@@ -1156,8 +1155,6 @@ struct kvm_x86_ops {
 	int (*get_tdp_level)(struct kvm_vcpu *vcpu);
 	u64 (*get_mt_mask)(struct kvm_vcpu *vcpu, gfn_t gfn, bool is_mmio);
 
-	void (*set_tdp_cr3)(struct kvm_vcpu *vcpu, unsigned long cr3);
-
 	bool (*has_wbinvd_exit)(void);
 
 	u64 (*read_l1_tsc_offset)(struct kvm_vcpu *vcpu);

arch/x86/kvm/mmu.h

@@ -95,11 +95,11 @@ static inline unsigned long kvm_get_active_pcid(struct kvm_vcpu *vcpu)
 	return kvm_get_pcid(vcpu, kvm_read_cr3(vcpu));
 }
 
-static inline void kvm_mmu_load_cr3(struct kvm_vcpu *vcpu)
+static inline void kvm_mmu_load_pgd(struct kvm_vcpu *vcpu)
 {
 	if (VALID_PAGE(vcpu->arch.mmu->root_hpa))
-		vcpu->arch.mmu->set_cr3(vcpu, vcpu->arch.mmu->root_hpa |
-					      kvm_get_active_pcid(vcpu));
+		kvm_x86_ops->set_cr3(vcpu, vcpu->arch.mmu->root_hpa |
+				     kvm_get_active_pcid(vcpu));
 }
 
 int kvm_tdp_page_fault(struct kvm_vcpu *vcpu, gpa_t gpa, u32 error_code,

arch/x86/kvm/mmu/mmu.c

@@ -4932,7 +4932,6 @@ static void init_kvm_tdp_mmu(struct kvm_vcpu *vcpu)
 	context->update_pte = nonpaging_update_pte;
 	context->shadow_root_level = kvm_x86_ops->get_tdp_level(vcpu);
 	context->direct_map = true;
-	context->set_cr3 = kvm_x86_ops->set_tdp_cr3;
 	context->get_guest_pgd = get_cr3;
 	context->get_pdptr = kvm_pdptr_read;
 	context->inject_page_fault = kvm_inject_page_fault;
@@ -5079,7 +5078,6 @@ static void init_kvm_softmmu(struct kvm_vcpu *vcpu)
 	struct kvm_mmu *context = vcpu->arch.mmu;
 
 	kvm_init_shadow_mmu(vcpu);
-	context->set_cr3           = kvm_x86_ops->set_cr3;
 	context->get_guest_pgd     = get_cr3;
 	context->get_pdptr         = kvm_pdptr_read;
 	context->inject_page_fault = kvm_inject_page_fault;

arch/x86/kvm/svm.c

@@ -2989,15 +2989,6 @@ static u64 nested_svm_get_tdp_pdptr(struct kvm_vcpu *vcpu, int index)
 	return pdpte;
 }
 
-static void nested_svm_set_tdp_cr3(struct kvm_vcpu *vcpu,
-				   unsigned long root)
-{
-	struct vcpu_svm *svm = to_svm(vcpu);
-
-	svm->vmcb->control.nested_cr3 = __sme_set(root);
-	mark_dirty(svm->vmcb, VMCB_NPT);
-}
-
 static void nested_svm_inject_npf_exit(struct kvm_vcpu *vcpu,
 				       struct x86_exception *fault)
 {
@@ -3033,7 +3024,6 @@ static void nested_svm_init_mmu_context(struct kvm_vcpu *vcpu)
 
 	vcpu->arch.mmu = &vcpu->arch.guest_mmu;
 	kvm_init_shadow_mmu(vcpu);
-	vcpu->arch.mmu->set_cr3           = nested_svm_set_tdp_cr3;
 	vcpu->arch.mmu->get_guest_pgd     = nested_svm_get_tdp_cr3;
 	vcpu->arch.mmu->get_pdptr         = nested_svm_get_tdp_pdptr;
 	vcpu->arch.mmu->inject_page_fault = nested_svm_inject_npf_exit;
@@ -5955,21 +5945,27 @@ STACK_FRAME_NON_STANDARD(svm_vcpu_run);
 static void svm_set_cr3(struct kvm_vcpu *vcpu, unsigned long root)
 {
 	struct vcpu_svm *svm = to_svm(vcpu);
+	bool update_guest_cr3 = true;
+	unsigned long cr3;
 
-	svm->vmcb->save.cr3 = __sme_set(root);
-	mark_dirty(svm->vmcb, VMCB_CR);
-}
-
-static void set_tdp_cr3(struct kvm_vcpu *vcpu, unsigned long root)
-{
-	struct vcpu_svm *svm = to_svm(vcpu);
+	cr3 = __sme_set(root);
+	if (npt_enabled) {
+		svm->vmcb->control.nested_cr3 = cr3;
+		mark_dirty(svm->vmcb, VMCB_NPT);
 
-	svm->vmcb->control.nested_cr3 = __sme_set(root);
-	mark_dirty(svm->vmcb, VMCB_NPT);
+		/* Loading L2's CR3 is handled by enter_svm_guest_mode.  */
+		if (is_guest_mode(vcpu))
+			update_guest_cr3 = false;
+		else if (test_bit(VCPU_EXREG_CR3, (ulong *)&vcpu->arch.regs_avail))
+			cr3 = vcpu->arch.cr3;
+		else /* CR3 is already up-to-date.  */
+			update_guest_cr3 = false;
+	}
 
-	/* Also sync guest cr3 here in case we live migrate */
-	svm->vmcb->save.cr3 = kvm_read_cr3(vcpu);
-	mark_dirty(svm->vmcb, VMCB_CR);
+	if (update_guest_cr3) {
+		svm->vmcb->save.cr3 = cr3;
+		mark_dirty(svm->vmcb, VMCB_CR);
+	}
 }
 
 static int is_disabled(void)
@@ -7418,8 +7414,6 @@ static struct kvm_x86_ops svm_x86_ops __ro_after_init = {
 	.read_l1_tsc_offset = svm_read_l1_tsc_offset,
 	.write_l1_tsc_offset = svm_write_l1_tsc_offset,
 
-	.set_tdp_cr3 = set_tdp_cr3,
-
 	.check_intercept = svm_check_intercept,
 	.handle_exit_irqoff = svm_handle_exit_irqoff,
 

arch/x86/kvm/vmx/nested.c

@@ -354,7 +354,6 @@ static void nested_ept_init_mmu_context(struct kvm_vcpu *vcpu)
 			VMX_EPT_EXECUTE_ONLY_BIT,
 			nested_ept_ad_enabled(vcpu),
 			nested_ept_get_eptp(vcpu));
-	vcpu->arch.mmu->set_cr3           = vmx_set_cr3;
 	vcpu->arch.mmu->get_guest_pgd     = nested_ept_get_eptp;
 	vcpu->arch.mmu->inject_page_fault = nested_ept_inject_page_fault;
 	vcpu->arch.mmu->get_pdptr         = kvm_pdptr_read;

arch/x86/kvm/vmx/vmx.c

@@ -7922,8 +7922,6 @@ static struct kvm_x86_ops vmx_x86_ops __ro_after_init = {
 	.read_l1_tsc_offset = vmx_read_l1_tsc_offset,
 	.write_l1_tsc_offset = vmx_write_l1_tsc_offset,
 
-	.set_tdp_cr3 = vmx_set_cr3,
-
 	.check_intercept = vmx_check_intercept,
 	.handle_exit_irqoff = vmx_handle_exit_irqoff,