ANDROID: KVM: arm64: Allow 16 host_smc handlers

Allow pKVM modules to register up to 16 host_smc handlers. The SMC will
be considered has handled on the first one returning True. Unhandled SMC
will be forwarded.

Bug: 357781595
Bug: 382397533
Change-Id: I58717927d7b47b8af5532ec2bfe57e022186e1d3
Signed-off-by: Vincent Donnefort <vdonnefort@google.com>

arch/arm64/include/asm/kvm_pkvm_module.h

@@ -93,8 +93,11 @@ enum pkvm_psci_notification {
  * @host_stage2_get_leaf:	Query the host's stage2 page-table entry for
  *				the page @phys.
  * @register_host_smc_handler:	@cb is called whenever the host issues an SMC
- *				pKVM couldn't handle. If @cb returns false, the
- *				SMC will be forwarded to EL3.
+ *				pKVM couldn't handle.
+ *				Up-to 16 handlers can be registered. The handler
+ *				order depends on the registration order. If no
+ *				handler return True, the SMC is forwarded to
+ *				EL3.
  * @register_default_trap_handler:
  *				@cb is called whenever EL2 traps EL1 and pKVM
  *				has not handled it. If @cb returns false, the

arch/arm64/kvm/hyp/include/nvhe/modules.h

@@ -18,6 +18,7 @@ int __pkvm_register_hcall(unsigned long hfn_hyp_va);
 int handle_host_dynamic_hcall(struct user_pt_regs *regs, int id);
 void __pkvm_close_module_registration(void);
 bool module_handle_host_perm_fault(struct user_pt_regs *regs, u64 esr, u64 addr);
+bool module_handle_host_smc(struct user_pt_regs *regs);
 #else
 static inline int __pkvm_init_module(void *module_init) { return -EOPNOTSUPP; }
 static inline int
@@ -29,4 +30,5 @@ handle_host_dynamic_hcall(struct kvm_cpu_context *host_ctxt, int id)
 }
 static inline void __pkvm_close_module_registration(void) { }
 bool module_handle_host_perm_fault(struct user_pt_regs *regs, u64 esr, u64 addr) { return false; }
+bool module_handle_host_smc(struct user_pt_regs *regs) { return false; }
 #endif

arch/arm64/kvm/hyp/nvhe/hyp-main.c

@@ -63,21 +63,10 @@ static inline void hyp_reqs_smccc_encode(unsigned long ret, struct kvm_cpu_conte
 
 void __kvm_hyp_host_forward_smc(struct kvm_cpu_context *host_ctxt);
 
-static bool (*default_host_smc_handler)(struct user_pt_regs *regs);
 static bool (*default_trap_handler)(struct user_pt_regs *regs);
 static bool (*unmask_serror)(void);
 static void (*mask_serror)(void);
 
-int __pkvm_register_host_smc_handler(bool (*cb)(struct user_pt_regs *))
-{
-	/*
-	 * Paired with smp_load_acquire(&default_host_smc_handler) in
-	 * handle_host_smc(). Ensure memory stores happening during a pKVM module
-	 * init are observed before executing the callback.
-	 */
-	return cmpxchg_release(&default_host_smc_handler, NULL, cb) ? -EBUSY : 0;
-}
-
 int __pkvm_register_default_trap_handler(bool (*cb)(struct user_pt_regs *))
 {
 	return cmpxchg(&default_trap_handler, NULL, cb) ? -EBUSY : 0;
@@ -1856,8 +1845,8 @@ static void handle_host_smc(struct kvm_cpu_context *host_ctxt)
 		handled = kvm_host_ffa_handler(host_ctxt, func_id);
 	if (!handled)
 		handled = kvm_host_scmi_handler(host_ctxt);
-	if (!handled && smp_load_acquire(&default_host_smc_handler))
-		handled = default_host_smc_handler(&host_ctxt->regs);
+	if (!handled)
+		handled = module_handle_host_smc(&host_ctxt->regs);
 	if (!handled) {
 		__hyp_exit();
 		__kvm_hyp_host_forward_smc(host_ctxt);

arch/arm64/kvm/hyp/nvhe/modules.c

@@ -132,6 +132,7 @@ static int __hyp_smp_processor_id(void)
 
 enum mod_handler_type {
 	HOST_FAULT_HANDLER = 0,
+	HOST_SMC_HANDLER,
 	NUM_MOD_HANDLER_TYPES,
 };
 
@@ -173,6 +174,11 @@ __register_host_perm_fault_handler(int (*cb)(struct user_pt_regs *regs, u64 esr,
 	return mod_handler_register(HOST_FAULT_HANDLER, cb);
 }
 
+static int __register_host_smc_handler(bool (*cb)(struct user_pt_regs *))
+{
+	return mod_handler_register(HOST_SMC_HANDLER, cb);
+}
+
 bool module_handle_host_perm_fault(struct user_pt_regs *regs, u64 esr, u64 addr)
 {
 	int (*cb)(struct user_pt_regs *regs, u64 esr, u64 addr);
@@ -186,6 +192,19 @@ bool module_handle_host_perm_fault(struct user_pt_regs *regs, u64 esr, u64 addr)
 	return false;
 }
 
+bool module_handle_host_smc(struct user_pt_regs *regs)
+{
+	bool (*cb)(struct user_pt_regs *regs);
+	int i;
+
+	for_each_mod_handler(HOST_SMC_HANDLER, cb, i) {
+		if (cb(regs))
+			return true;
+	}
+
+	return false;
+}
+
 const struct pkvm_module_ops module_ops = {
 	.create_private_mapping = __pkvm_create_private_mapping,
 	.alloc_module_va = __pkvm_alloc_module_va,
@@ -206,7 +225,7 @@ const struct pkvm_module_ops module_ops = {
 	.host_stage2_get_leaf = host_stage2_get_leaf,
 	.host_stage2_enable_lazy_pte = host_stage2_enable_lazy_pte,
 	.host_stage2_disable_lazy_pte = host_stage2_disable_lazy_pte,
-	.register_host_smc_handler = __pkvm_register_host_smc_handler,
+	.register_host_smc_handler = __register_host_smc_handler,
 	.register_default_trap_handler = __pkvm_register_default_trap_handler,
 	.register_illegal_abt_notifier = __pkvm_register_illegal_abt_notifier,
 	.register_psci_notifier = __pkvm_register_psci_notifier,