KVM: x86/mmu: Use MMU's roles to compute last non-leaf level

Use the MMU's role to get CR4.PSE when determining the last level at
which the guest _cannot_ create a non-leaf PTE, i.e. cannot create a
huge page.

Note, the existing logic is arguably wrong when considering 5-level
paging and the case where 1gb pages aren't supported.  In practice, the
logic is confusing but not broken, because except for 32-bit non-PAE
paging, bit 7 (_PAGE_PSE) bit is reserved when a huge page isn't supported at
that level.  I.e. setting bit 7 will terminate the guest walk one way or
another.  Furthermore, last_nonleaf_level is only consulted after KVM has
verified there are no reserved bits set.

All that confusion will be addressed in a future patch by dropping
last_nonleaf_level entirely.  For now, massage the code to continue the
march toward using mmu_role for (almost) all MMU computations.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210622175739.3610207-35-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/mmu/mmu.c

@@ -4504,12 +4504,12 @@ static void update_pkru_bitmask(struct kvm_mmu *mmu)
 	}
 }
 
-static void update_last_nonleaf_level(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu)
+static void update_last_nonleaf_level(struct kvm_mmu *mmu)
 {
 	unsigned root_level = mmu->root_level;
 
 	mmu->last_nonleaf_level = root_level;
-	if (root_level == PT32_ROOT_LEVEL && is_pse(vcpu))
+	if (root_level == PT32_ROOT_LEVEL && is_cr4_pse(mmu))
 		mmu->last_nonleaf_level++;
 }
 
@@ -4666,7 +4666,7 @@ static void init_kvm_tdp_mmu(struct kvm_vcpu *vcpu)
 
 	update_permission_bitmask(context, false);
 	update_pkru_bitmask(context);
-	update_last_nonleaf_level(vcpu, context);
+	update_last_nonleaf_level(context);
 	reset_tdp_shadow_zero_bits_mask(vcpu, context);
 }
 
@@ -4724,7 +4724,7 @@ static void shadow_mmu_init_context(struct kvm_vcpu *vcpu, struct kvm_mmu *conte
 		reset_rsvds_bits_mask(vcpu, context);
 		update_permission_bitmask(context, false);
 		update_pkru_bitmask(context);
-		update_last_nonleaf_level(vcpu, context);
+		update_last_nonleaf_level(context);
 	}
 	context->shadow_root_level = new_role.base.level;
 
@@ -4831,7 +4831,7 @@ void kvm_init_shadow_ept_mmu(struct kvm_vcpu *vcpu, bool execonly,
 	context->direct_map = false;
 
 	update_permission_bitmask(context, true);
-	update_last_nonleaf_level(vcpu, context);
+	update_last_nonleaf_level(context);
 	update_pkru_bitmask(context);
 	reset_rsvds_bits_mask_ept(vcpu, context, execonly);
 	reset_ept_shadow_zero_bits_mask(vcpu, context, execonly);
@@ -4929,7 +4929,7 @@ static void init_kvm_nested_mmu(struct kvm_vcpu *vcpu)
 
 	update_permission_bitmask(g_context, false);
 	update_pkru_bitmask(g_context);
-	update_last_nonleaf_level(vcpu, g_context);
+	update_last_nonleaf_level(g_context);
 }
 
 void kvm_init_mmu(struct kvm_vcpu *vcpu)