KVM: x86/mmu: Get nested MMU's root level from the MMU's role

Initialize the MMU's (guest) root_level using its mmu_role instead of
redoing the calculations.  The role_regs used to calculate the mmu_role
are initialized from the vCPU, i.e. this should be a complete nop.

No functional change intended.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210622175739.3610207-40-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/mmu/mmu.c

@@ -4874,6 +4874,7 @@ static void init_kvm_nested_mmu(struct kvm_vcpu *vcpu)
 	g_context->get_guest_pgd     = get_cr3;
 	g_context->get_pdptr         = kvm_pdptr_read;
 	g_context->inject_page_fault = kvm_inject_page_fault;
+	g_context->root_level        = new_role.base.level;
 
 	/*
 	 * L2 page tables are never shadowed, so there is no need to sync
@@ -4890,19 +4891,14 @@ static void init_kvm_nested_mmu(struct kvm_vcpu *vcpu)
 	 * the gva_to_gpa functions between mmu and nested_mmu are swapped.
 	 */
 	if (!is_paging(vcpu)) {
-		g_context->root_level = 0;
 		g_context->gva_to_gpa = nonpaging_gva_to_gpa_nested;
 	} else if (is_long_mode(vcpu)) {
-		g_context->root_level = is_la57_mode(vcpu) ?
-					PT64_ROOT_5LEVEL : PT64_ROOT_4LEVEL;
 		reset_rsvds_bits_mask(vcpu, g_context);
 		g_context->gva_to_gpa = paging64_gva_to_gpa_nested;
 	} else if (is_pae(vcpu)) {
-		g_context->root_level = PT32E_ROOT_LEVEL;
 		reset_rsvds_bits_mask(vcpu, g_context);
 		g_context->gva_to_gpa = paging64_gva_to_gpa_nested;
 	} else {
-		g_context->root_level = PT32_ROOT_LEVEL;
 		reset_rsvds_bits_mask(vcpu, g_context);
 		g_context->gva_to_gpa = paging32_gva_to_gpa_nested;
 	}