KVM: x86/mmu: store shadow EFER.NX in the MMU role

Now that the MMU role is separate from the CPU role, it can be a
truthful description of the format of the shadow pages.  This includes
whether the shadow pages use the NX bit; so force the efer_nx field
of the MMU role when TDP is disabled, and remove the hardcoding it in
the callers of reset_shadow_zero_bits_mask.

In fact, the initialization of reserved SPTE bits can now be made common
to shadow paging and shadow NPT; move it to shadow_mmu_init_context.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/mmu/mmu.c

@@ -4473,16 +4473,6 @@ static inline u64 reserved_hpa_bits(void)
 static void reset_shadow_zero_bits_mask(struct kvm_vcpu *vcpu,
 					struct kvm_mmu *context)
 {
-	/*
-	 * KVM uses NX when TDP is disabled to handle a variety of scenarios,
-	 * notably for huge SPTEs if iTLB multi-hit mitigation is enabled and
-	 * to generate correct permissions for CR0.WP=0/CR4.SMEP=1/EFER.NX=0.
-	 * The iTLB multi-hit workaround can be toggled at any time, so assume
-	 * NX can be used by any non-nested shadow MMU to avoid having to reset
-	 * MMU contexts.  Note, KVM forces EFER.NX=1 when TDP is disabled.
-	 */
-	bool uses_nx = is_efer_nx(context) || !tdp_enabled;
-
 	/* @amd adds a check on bit of SPTEs, which KVM shouldn't use anyways. */
 	bool is_amd = true;
 	/* KVM doesn't use 2-level page tables for the shadow MMU. */
@@ -4494,7 +4484,8 @@ static void reset_shadow_zero_bits_mask(struct kvm_vcpu *vcpu,
 
 	shadow_zero_check = &context->shadow_zero_check;
 	__reset_rsvds_bits_mask(shadow_zero_check, reserved_hpa_bits(),
-				context->shadow_root_level, uses_nx,
+				context->shadow_root_level,
+				context->mmu_role.base.efer_nx,
 				guest_can_use_gbpages(vcpu), is_pse, is_amd);
 
 	if (!shadow_me_mask)
@@ -4858,6 +4849,16 @@ kvm_calc_shadow_mmu_root_page_role(struct kvm_vcpu *vcpu,
 	else
 		role.base.level = PT64_ROOT_4LEVEL;
 
+	/*
+	 * KVM forces EFER.NX=1 when TDP is disabled, reflect it in the MMU role.
+	 * KVM uses NX when TDP is disabled to handle a variety of scenarios,
+	 * notably for huge SPTEs if iTLB multi-hit mitigation is enabled and
+	 * to generate correct permissions for CR0.WP=0/CR4.SMEP=1/EFER.NX=0.
+	 * The iTLB multi-hit workaround can be toggled at any time, so assume
+	 * NX can be used by any non-nested shadow MMU to avoid having to reset
+	 * MMU contexts.
+	 */
+	role.base.efer_nx = true;
 	return role;
 }