KVM: x86/mmu: Grab shadow root level from mmu_role for shadow MMUs

Use the mmu_role to initialize shadow root level instead of assuming the
level of KVM's shadow root (host) is the same as that of the guest root,
or in the case of 32-bit non-PAE paging where KVM forces PAE paging.
For nested NPT, the shadow root level cannot be adapted to L1's NPT root
level and is instead always the TDP root level because NPT uses the
current host CR0/CR4/EFER, e.g. 64-bit KVM can't drop into 32-bit PAE to
shadow L1's NPT.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210622175739.3610207-20-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/mmu/mmu.c

@@ -3898,7 +3898,6 @@ static void nonpaging_init_context(struct kvm_vcpu *vcpu,
 	context->sync_page = nonpaging_sync_page;
 	context->invlpg = NULL;
 	context->root_level = 0;
-	context->shadow_root_level = PT32E_ROOT_LEVEL;
 	context->direct_map = true;
 	context->nx = false;
 }
@@ -4466,10 +4465,10 @@ static void update_last_nonleaf_level(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu
 
 static void paging64_init_context_common(struct kvm_vcpu *vcpu,
 					 struct kvm_mmu *context,
-					 int level)
+					 int root_level)
 {
 	context->nx = is_nx(vcpu);
-	context->root_level = level;
+	context->root_level = root_level;
 
 	reset_rsvds_bits_mask(vcpu, context);
 	update_permission_bitmask(vcpu, context, false);
@@ -4481,7 +4480,6 @@ static void paging64_init_context_common(struct kvm_vcpu *vcpu,
 	context->gva_to_gpa = paging64_gva_to_gpa;
 	context->sync_page = paging64_sync_page;
 	context->invlpg = paging64_invlpg;
-	context->shadow_root_level = level;
 	context->direct_map = false;
 }
 
@@ -4509,7 +4507,6 @@ static void paging32_init_context(struct kvm_vcpu *vcpu,
 	context->gva_to_gpa = paging32_gva_to_gpa;
 	context->sync_page = paging32_sync_page;
 	context->invlpg = paging32_invlpg;
-	context->shadow_root_level = PT32E_ROOT_LEVEL;
 	context->direct_map = false;
 }
 
@@ -4669,6 +4666,8 @@ static void shadow_mmu_init_context(struct kvm_vcpu *vcpu, struct kvm_mmu *conte
 	else
 		paging32_init_context(vcpu, context);
 
+	context->shadow_root_level = new_role.base.level;
+
 	context->mmu_role.as_u64 = new_role.as_u64;
 	reset_shadow_zero_bits_mask(vcpu, context);
 }
@@ -4704,16 +4703,9 @@ void kvm_init_shadow_npt_mmu(struct kvm_vcpu *vcpu, unsigned long cr0,
 
 	__kvm_mmu_new_pgd(vcpu, nested_cr3, new_role.base);
 
-	if (new_role.as_u64 != context->mmu_role.as_u64) {
+	if (new_role.as_u64 != context->mmu_role.as_u64)
 		shadow_mmu_init_context(vcpu, context, cr0, cr4, efer, new_role);
 
-		/*
-		 * Override the level set by the common init helper, nested TDP
-		 * always uses the host's TDP configuration.
-		 */
-		context->shadow_root_level = new_role.base.level;
-	}
-
 	/*
 	 * Redo the shadow bits, the reset done by shadow_mmu_init_context()
 	 * (above) may use the wrong shadow_root_level.