KVM: nSVM: Set the shadow root level to the TDP level for nested NPT

Override the shadow root level in the MMU context when configuring
NPT for shadowing nested NPT.  The level is always tied to the TDP level
of the host, not whatever level the guest happens to be using.

Fixes: 096586fd ("KVM: nSVM: Correctly set the shadow NPT root level in its MMU role")
Cc: stable@vger.kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210305011101.3597423-2-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/mmu/mmu.c

@@ -4649,12 +4649,17 @@ void kvm_init_shadow_npt_mmu(struct kvm_vcpu *vcpu, u32 cr0, u32 cr4, u32 efer,
 	struct kvm_mmu *context = &vcpu->arch.guest_mmu;
 	union kvm_mmu_role new_role = kvm_calc_shadow_npt_root_page_role(vcpu);
 
-	context->shadow_root_level = new_role.base.level;
-
 	__kvm_mmu_new_pgd(vcpu, nested_cr3, new_role.base, false, false);
 
-	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;
+	}
 }
 EXPORT_SYMBOL_GPL(kvm_init_shadow_npt_mmu);