KVM: nVMX: Do not inherit quadrant and invalid for the root shadow EPT

Explicitly zero out quadrant and invalid instead of inheriting them from
the root_mmu.  Functionally, this patch is a nop as we (should) never
set quadrant for a direct mapped (EPT) root_mmu and nested EPT is only
allowed if EPT is used for L1, and the root_mmu will never be invalid at
this point.

Explicitly setting flags sets the stage for repurposing the legacy
paging bits in role, e.g. nxe, cr0_wp, and sm{a,e}p_andnot_wp, at which
point 'smm' would be the only flag to be inherited from root_mmu.

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/mmu.c

@@ -4918,18 +4918,23 @@ static union kvm_mmu_role
 kvm_calc_shadow_ept_root_page_role(struct kvm_vcpu *vcpu, bool accessed_dirty,
 				   bool execonly)
 {
-	union kvm_mmu_role role;
+	union kvm_mmu_role role = {0};
+	union kvm_mmu_page_role root_base = vcpu->arch.root_mmu.mmu_role.base;
 
-	/* Base role is inherited from root_mmu */
-	role.base.word = vcpu->arch.root_mmu.mmu_role.base.word;
-	role.ext = kvm_calc_mmu_role_ext(vcpu);
+	/* Legacy paging and SMM flags are inherited from root_mmu */
+	role.base.smm = root_base.smm;
+	role.base.nxe = root_base.nxe;
+	role.base.cr0_wp = root_base.cr0_wp;
+	role.base.smep_andnot_wp = root_base.smep_andnot_wp;
+	role.base.smap_andnot_wp = root_base.smap_andnot_wp;
 
 	role.base.level = PT64_ROOT_4LEVEL;
 	role.base.direct = false;
 	role.base.ad_disabled = !accessed_dirty;
 	role.base.guest_mode = true;
 	role.base.access = ACC_ALL;
 
+	role.ext = kvm_calc_mmu_role_ext(vcpu);
 	role.ext.execonly = execonly;
 
 	return role;