KVM: nSVM: Correctly set the shadow NPT root level in its MMU role

Move the initialization of shadow NPT MMU's shadow_root_level into
kvm_init_shadow_npt_mmu() and explicitly set the level in the shadow NPT
MMU's role to be the TDP level.  This ensures the role and MMU levels
are synchronized and also initialized before __kvm_mmu_new_pgd(), which
consumes the level when attempting a fast PGD switch.

Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
Fixes: 9fa72119 ("kvm: x86: Introduce kvm_mmu_calc_root_page_role()")
Fixes: a506fdd2 ("KVM: nSVM: implement nested_svm_load_cr3() and use it for host->guest switch")
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Message-Id: <20200716034122.5998-2-sean.j.christopherson@intel.com>
Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Tested-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/mmu/mmu.c

@@ -4963,6 +4963,9 @@ void kvm_init_shadow_npt_mmu(struct kvm_vcpu *vcpu, u32 cr0, u32 cr4, u32 efer,
 	union kvm_mmu_role new_role =
 		kvm_calc_shadow_mmu_root_page_role(vcpu, false);
 
+	new_role.base.level = vcpu->arch.tdp_level;
+	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)

arch/x86/kvm/svm/nested.c

@@ -85,7 +85,6 @@ static void nested_svm_init_mmu_context(struct kvm_vcpu *vcpu)
 	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;
-	vcpu->arch.mmu->shadow_root_level = vcpu->arch.tdp_level;
 	reset_shadow_zero_bits_mask(vcpu, vcpu->arch.mmu);
 	vcpu->arch.walk_mmu              = &vcpu->arch.nested_mmu;
 }