KVM: arm64: Restrict host hypercalls when pKVM is enabled

index 6f6ff072acbd..44369b99a57e 100644
@@ -1128,5 +1128,6 @@ bool cpus_are_stuck_in_kernel(void)
 {
 	bool smp_spin_tables = (num_possible_cpus() > 1 && !have_cpu_die());
 
-	return !!cpus_stuck_in_kernel || smp_spin_tables;
+	return !!cpus_stuck_in_kernel || smp_spin_tables ||
+		is_protected_kvm_enabled();
 }

index fe102cd2e518..9506cf88fa0e 100644
@@ -1579,25 +1579,33 @@ static void cpu_set_hyp_vector(void)
 		kvm_call_hyp_nvhe(__pkvm_cpu_set_vector, data->slot);
 }
 
-static void cpu_hyp_reinit(void)
+static void cpu_hyp_init_context(void)
 {
 	kvm_init_host_cpu_context(&this_cpu_ptr_hyp_sym(kvm_host_data)->host_ctxt);
 
-	cpu_hyp_reset();
-
-	if (is_kernel_in_hyp_mode())
-		kvm_timer_init_vhe();
-	else
+	if (!is_kernel_in_hyp_mode())
 		cpu_init_hyp_mode();
+}
 
+static void cpu_hyp_init_features(void)
+{
 	cpu_set_hyp_vector();
-
 	kvm_arm_init_debug();
 
+	if (is_kernel_in_hyp_mode())
+		kvm_timer_init_vhe();
+
 	if (vgic_present)
 		kvm_vgic_init_cpu_hardware();
 }
 
+static void cpu_hyp_reinit(void)
+{
+	cpu_hyp_reset();
+	cpu_hyp_init_context();
+	cpu_hyp_init_features();
+}
+
 static void _kvm_arch_hardware_enable(void *discard)
 {
 	if (!__this_cpu_read(kvm_arm_hardware_enabled)) {

@@ -1788,10 +1796,17 @@ static int do_pkvm_init(u32 hyp_va_bits)
 	int ret;
 
 	preempt_disable();
-	hyp_install_host_vector();
+	cpu_hyp_init_context();
 	ret = kvm_call_hyp_nvhe(__pkvm_init, hyp_mem_base, hyp_mem_size,
 				num_possible_cpus(), kern_hyp_va(per_cpu_base),
 				hyp_va_bits);
+	cpu_hyp_init_features();
+
+	/*
+	 * The stub hypercalls are now disabled, so set our local flag to
+	 * prevent a later re-init attempt in kvm_arch_hardware_enable().
+	 */
+	__this_cpu_write(kvm_arm_hardware_enabled, 1);
 	preempt_enable();
 
 	return ret;

index 9506cf88fa0e..13bbf35896cd 100644
@@ -1986,9 +1986,25 @@ static int init_hyp_mode(void)
 	return err;
 }
 
-static void _kvm_host_prot_finalize(void *discard)
+static void _kvm_host_prot_finalize(void *arg)
 {
-	WARN_ON(kvm_call_hyp_nvhe(__pkvm_prot_finalize));
+	int *err = arg;
+
+	if (WARN_ON(kvm_call_hyp_nvhe(__pkvm_prot_finalize)))
+		WRITE_ONCE(*err, -EINVAL);
+}
+
+static int pkvm_drop_host_privileges(void)
+{
+	int ret = 0;
+
+	/*
+	 * Flip the static key upfront as that may no longer be possible
+	 * once the host stage 2 is installed.
+	 */
+	static_branch_enable(&kvm_protected_mode_initialized);
+	on_each_cpu(_kvm_host_prot_finalize, &ret, 1);
+	return ret;
 }
 
 static int finalize_hyp_mode(void)

@@ -2002,15 +2018,7 @@ static int finalize_hyp_mode(void)
 	 * None of other sections should ever be introspected.
 	 */
 	kmemleak_free_part(__hyp_bss_start, __hyp_bss_end - __hyp_bss_start);
-
-	/*
-	 * Flip the static key upfront as that may no longer be possible
-	 * once the host stage 2 is installed.
-	 */
-	static_branch_enable(&kvm_protected_mode_initialized);
-	on_each_cpu(_kvm_host_prot_finalize, NULL, 1);
-
-	return 0;
+	return pkvm_drop_host_privileges();
 }
 
 struct kvm_vcpu *kvm_mpidr_to_vcpu(struct kvm *kvm, unsigned long mpidr)

index bacd493a4eac..cafe17e5fa8f 100644
@@ -123,6 +123,9 @@ int __pkvm_prot_finalize(void)
 	struct kvm_s2_mmu *mmu = &host_kvm.arch.mmu;
 	struct kvm_nvhe_init_params *params = this_cpu_ptr(&kvm_init_params);
 
+	if (params->hcr_el2 & HCR_VM)
+		return -EPERM;
+
 	params->vttbr = kvm_get_vttbr(mmu);
 	params->vtcr = host_kvm.arch.vtcr;
 	params->hcr_el2 |= HCR_VM;

index e86045ac43ba..68630fd382c5 100644
@@ -43,27 +43,30 @@
 
 #define KVM_HOST_SMCCC_FUNC(name) KVM_HOST_SMCCC_ID(__KVM_HOST_SMCCC_FUNC_##name)
 
+/* Hypercalls available only prior to pKVM finalisation */
 #define __KVM_HOST_SMCCC_FUNC___kvm_hyp_init			0
-#define __KVM_HOST_SMCCC_FUNC___kvm_vcpu_run			1
-#define __KVM_HOST_SMCCC_FUNC___kvm_flush_vm_context		2
-#define __KVM_HOST_SMCCC_FUNC___kvm_tlb_flush_vmid_ipa		3
-#define __KVM_HOST_SMCCC_FUNC___kvm_tlb_flush_vmid		4
-#define __KVM_HOST_SMCCC_FUNC___kvm_flush_cpu_context		5
-#define __KVM_HOST_SMCCC_FUNC___kvm_timer_set_cntvoff		6
-#define __KVM_HOST_SMCCC_FUNC___kvm_enable_ssbs			7
-#define __KVM_HOST_SMCCC_FUNC___vgic_v3_get_gic_config		8
-#define __KVM_HOST_SMCCC_FUNC___vgic_v3_read_vmcr		9
-#define __KVM_HOST_SMCCC_FUNC___vgic_v3_write_vmcr		10
-#define __KVM_HOST_SMCCC_FUNC___vgic_v3_init_lrs		11
-#define __KVM_HOST_SMCCC_FUNC___kvm_get_mdcr_el2		12
-#define __KVM_HOST_SMCCC_FUNC___vgic_v3_save_aprs		13
-#define __KVM_HOST_SMCCC_FUNC___vgic_v3_restore_aprs		14
-#define __KVM_HOST_SMCCC_FUNC___pkvm_init			15
-#define __KVM_HOST_SMCCC_FUNC___pkvm_host_share_hyp		16
-#define __KVM_HOST_SMCCC_FUNC___pkvm_create_private_mapping	17
-#define __KVM_HOST_SMCCC_FUNC___pkvm_cpu_set_vector		18
-#define __KVM_HOST_SMCCC_FUNC___pkvm_prot_finalize		19
-#define __KVM_HOST_SMCCC_FUNC___kvm_adjust_pc			20
+#define __KVM_HOST_SMCCC_FUNC___kvm_get_mdcr_el2		1
+#define __KVM_HOST_SMCCC_FUNC___pkvm_init			2
+#define __KVM_HOST_SMCCC_FUNC___pkvm_create_private_mapping	3
+#define __KVM_HOST_SMCCC_FUNC___pkvm_cpu_set_vector		4
+#define __KVM_HOST_SMCCC_FUNC___kvm_enable_ssbs			5
+#define __KVM_HOST_SMCCC_FUNC___vgic_v3_init_lrs		6
+#define __KVM_HOST_SMCCC_FUNC___vgic_v3_get_gic_config		7
+#define __KVM_HOST_SMCCC_FUNC___pkvm_prot_finalize		8
+
+/* Hypercalls available after pKVM finalisation */
+#define __KVM_HOST_SMCCC_FUNC___pkvm_host_share_hyp		9
+#define __KVM_HOST_SMCCC_FUNC___kvm_adjust_pc			10
+#define __KVM_HOST_SMCCC_FUNC___kvm_vcpu_run			11
+#define __KVM_HOST_SMCCC_FUNC___kvm_flush_vm_context		12
+#define __KVM_HOST_SMCCC_FUNC___kvm_tlb_flush_vmid_ipa		13
+#define __KVM_HOST_SMCCC_FUNC___kvm_tlb_flush_vmid		14
+#define __KVM_HOST_SMCCC_FUNC___kvm_flush_cpu_context		15
+#define __KVM_HOST_SMCCC_FUNC___kvm_timer_set_cntvoff		16
+#define __KVM_HOST_SMCCC_FUNC___vgic_v3_read_vmcr		17
+#define __KVM_HOST_SMCCC_FUNC___vgic_v3_write_vmcr		18
+#define __KVM_HOST_SMCCC_FUNC___vgic_v3_save_aprs		19
+#define __KVM_HOST_SMCCC_FUNC___vgic_v3_restore_aprs		20
 
 #ifndef __ASSEMBLY__
 

index 2da6aa8da868..8566805ef62c 100644
@@ -165,36 +165,51 @@ typedef void (*hcall_t)(struct kvm_cpu_context *);
 #define HANDLE_FUNC(x)	[__KVM_HOST_SMCCC_FUNC_##x] = (hcall_t)handle_##x
 
 static const hcall_t host_hcall[] = {
-	HANDLE_FUNC(__kvm_vcpu_run),
+	/* ___kvm_hyp_init */
+	HANDLE_FUNC(__kvm_get_mdcr_el2),
+	HANDLE_FUNC(__pkvm_init),
+	HANDLE_FUNC(__pkvm_create_private_mapping),
+	HANDLE_FUNC(__pkvm_cpu_set_vector),
+	HANDLE_FUNC(__kvm_enable_ssbs),
+	HANDLE_FUNC(__vgic_v3_init_lrs),
+	HANDLE_FUNC(__vgic_v3_get_gic_config),
+	HANDLE_FUNC(__pkvm_prot_finalize),
+
+	HANDLE_FUNC(__pkvm_host_share_hyp),
 	HANDLE_FUNC(__kvm_adjust_pc),
+	HANDLE_FUNC(__kvm_vcpu_run),
 	HANDLE_FUNC(__kvm_flush_vm_context),
 	HANDLE_FUNC(__kvm_tlb_flush_vmid_ipa),
 	HANDLE_FUNC(__kvm_tlb_flush_vmid),
 	HANDLE_FUNC(__kvm_flush_cpu_context),
 	HANDLE_FUNC(__kvm_timer_set_cntvoff),
-	HANDLE_FUNC(__kvm_enable_ssbs),
-	HANDLE_FUNC(__vgic_v3_get_gic_config),
 	HANDLE_FUNC(__vgic_v3_read_vmcr),
 	HANDLE_FUNC(__vgic_v3_write_vmcr),
-	HANDLE_FUNC(__vgic_v3_init_lrs),
-	HANDLE_FUNC(__kvm_get_mdcr_el2),
 	HANDLE_FUNC(__vgic_v3_save_aprs),
 	HANDLE_FUNC(__vgic_v3_restore_aprs),
-	HANDLE_FUNC(__pkvm_init),
-	HANDLE_FUNC(__pkvm_cpu_set_vector),
-	HANDLE_FUNC(__pkvm_host_share_hyp),
-	HANDLE_FUNC(__pkvm_create_private_mapping),
-	HANDLE_FUNC(__pkvm_prot_finalize),
 };
 
 static void handle_host_hcall(struct kvm_cpu_context *host_ctxt)
 {
 	DECLARE_REG(unsigned long, id, host_ctxt, 0);
+	unsigned long hcall_min = 0;
 	hcall_t hfn;
 
+	/*
+	 * If pKVM has been initialised then reject any calls to the
+	 * early "privileged" hypercalls. Note that we cannot reject
+	 * calls to __pkvm_prot_finalize for two reasons: (1) The static
+	 * key used to determine initialisation must be toggled prior to
+	 * finalisation and (2) finalisation is performed on a per-CPU
+	 * basis. This is all fine, however, since __pkvm_prot_finalize
+	 * returns -EPERM after the first call for a given CPU.
+	 */
+	if (static_branch_unlikely(&kvm_protected_mode_initialized))
+		hcall_min = __KVM_HOST_SMCCC_FUNC___pkvm_prot_finalize;
+
 	id -= KVM_HOST_SMCCC_ID(0);
 
-	if (unlikely(id >= ARRAY_SIZE(host_hcall)))
+	if (unlikely(id < hcall_min || id >= ARRAY_SIZE(host_hcall)))
 		goto inval;
 
 	hfn = host_hcall[id];