feat(lfa): serialize activate across CPUs and manage rendezvous policy

Track activation state across CPUs so skip-rendezvous activations don’t
block or interleave. Split activate into prepare/finish to latch the
rendezvous policy, notify the platform once per activation, and only
clear activation_pending after all callers finish. Return LFA_BUSY for
conflicting skip requests and LFA_CALL_AGAIN for multi‑stage activations.

Change-Id: Id5a71fb6db12fe240e2bc1c9000606df935374b2
Signed-off-by: Manish V Badarkhe <Manish.Badarkhe@arm.com>
Signed-off-by: John Powell <john.powell@arm.com>

1 files changed, 209 insertions, 53 deletions

diff --git a/services/std_svc/lfa/lfa_main.c b/services/std_svc/lfa/lfa_main.c
index 0022e0331..2f76756bc 100644
--- a/services/std_svc/lfa/lfa_main.c
+++ b/services/std_svc/lfa/lfa_main.c
@@ -15,10 +15,22 @@
 #include <services/rmmd_rmm_lfa.h>
 #include <smccc_helpers.h>
 
-static uint32_t lfa_component_count;
 static plat_lfa_component_info_t *lfa_components;
 static struct lfa_component_status current_activation;
-static bool is_lfa_initialized;
+
+/*
+ * Multiple cores call into LFA service which shares these variables, so ensure
+ * that any accesses to these variables go back to memory. These are sort of
+ * "lazy" state variables where timing isn't really critical so we aren't
+ * explicitly using mutex for access control but we just want to make sure
+ * nothing is optimized away.
+ */
+static volatile uint32_t lfa_component_count;
+static volatile bool is_lfa_initialized;
+static volatile bool activation_in_progress;
+static volatile bool activation_skip_cpu_rendezvous;
+static volatile uint32_t activation_users;
+static volatile bool activation_failed;
 
 /*
  * Spinlock to serialize LFA operations (PRIME, ACTIVATE).
@@ -32,6 +44,11 @@ void lfa_reset_activation(void)
 {
 	current_activation.component_id = LFA_INVALID_COMPONENT;
 	current_activation.prime_status = PRIME_NONE;
+	current_activation.cpu_rendezvous = false;
+	activation_in_progress = false;
+	activation_skip_cpu_rendezvous = false;
+	activation_users = 0U;
+	activation_failed = false;
 }
 
 static int convert_to_lfa_error(int ret)
@@ -114,54 +131,6 @@ static int lfa_cancel(uint32_t component_id)
 	return ret;
 }
 
-static int lfa_activate(uint32_t component_id, uint64_t flags,
-			uint64_t ep_address, uint64_t context_id)
-{
-	int ret = LFA_ACTIVATION_FAILED;
-	struct lfa_component_ops *activator;
-
-	if ((lfa_component_count == 0U) ||
-	    (!lfa_components[component_id].activation_pending) ||
-	    (current_activation.prime_status != PRIME_COMPLETE)) {
-		return LFA_COMPONENT_WRONG_STATE;
-	}
-
-	if ((component_id >= lfa_component_count) ||
-	    (current_activation.component_id != component_id)) {
-		return LFA_INVALID_PARAMETERS;
-	}
-
-	activator = lfa_components[component_id].activator;
-	if (activator == NULL) {
-		return LFA_NOT_SUPPORTED;
-	}
-
-	ret = plat_lfa_notify_activate(component_id);
-	if (ret != 0) {
-		return LFA_ACTIVATION_FAILED;
-	}
-
-	/* If caller requests it, see if we can skip CPU rendezvous. */
-	if (flags & LFA_SKIP_CPU_RENDEZVOUS_BIT) {
-		if (!activator->cpu_rendezvous_required) {
-			INFO("Caller requested skip CPU rendezvous.\n");
-			current_activation.cpu_rendezvous = false;
-		} else {
-			ERROR("CPU rendezvous cannot be skipped!\n");
-			return LFA_INVALID_PARAMETERS;
-		}
-	}
-
-	ret = activator->activate(&current_activation, ep_address, context_id);
-
-	/* Clear pending flag on successful activation. */
-	if (ret == LFA_SUCCESS) {
-		lfa_components[component_id].activation_pending = false;
-	}
-
-	return ret;
-}
-
 static int lfa_prime(uint32_t component_id, uint64_t *flags)
 {
 	int ret = LFA_SUCCESS;
@@ -261,6 +230,110 @@ int lfa_setup(void)
 	return 0;
 }
 
+static int lfa_activate_prepare(uint32_t component_id, uint64_t flags,
+				struct lfa_component_ops **activator)
+{
+	int ret = LFA_ACTIVATION_FAILED;
+	/* First caller decides activation policy and performs platform notify. */
+	bool first_cpu = !activation_in_progress;
+
+	/* Check if fw_seq_id is in range. */
+	if ((component_id >= lfa_component_count) ||
+	    (current_activation.component_id != component_id)) {
+		return LFA_INVALID_PARAMETERS;
+	}
+
+	if ((lfa_component_count == 0U) ||
+	    (!lfa_components[component_id].activation_pending) ||
+	    (current_activation.prime_status != PRIME_COMPLETE)) {
+		return LFA_COMPONENT_WRONG_STATE;
+	}
+
+	if (lfa_components[component_id].activator == NULL) {
+		return LFA_NOT_SUPPORTED;
+	}
+
+	*activator = lfa_components[component_id].activator;
+
+	if (first_cpu) {
+		activation_failed = false;
+
+		/*
+		 * If rendezvous is optional for this component, default to
+		 * rendezvous unless caller explicitly asks to skip it.
+		 * This choice is latched for the whole activation.
+		 */
+		if (!(*activator)->cpu_rendezvous_required &&
+		    ((flags & LFA_SKIP_CPU_RENDEZVOUS_BIT) == 0U)) {
+			current_activation.cpu_rendezvous = true;
+		} else {
+			current_activation.cpu_rendezvous =
+				(*activator)->cpu_rendezvous_required;
+		}
+		activation_skip_cpu_rendezvous = false;
+	}
+	/*
+	 * Pass skip_cpu_rendezvous (flag[0]) only if flag[0]==1
+	 * & CPU_RENDEZVOUS is not required.
+	 */
+	if (flags & LFA_SKIP_CPU_RENDEZVOUS_BIT) {
+		if (!(*activator)->cpu_rendezvous_required) {
+			/*
+			 * Late skip request is rejected if activation already
+			 * started without skip.
+			 */
+			if (!first_cpu && !activation_skip_cpu_rendezvous) {
+				return LFA_BUSY;
+			}
+			INFO("Skipping rendezvous requested by caller.\n");
+			current_activation.cpu_rendezvous = false;
+			activation_skip_cpu_rendezvous = true;
+		}
+		/*
+		 * Return error if caller tries to skip rendezvous when
+		 * it is required.
+		 */
+		else {
+			ERROR("CPU Rendezvous is required, can't skip.\n");
+			return LFA_INVALID_PARAMETERS;
+		}
+	}
+
+	if (first_cpu) {
+		/* Notify platform once per activation round. */
+		ret = plat_lfa_notify_activate(component_id);
+		if (ret != 0) {
+			return LFA_ACTIVATION_FAILED;
+		}
+		activation_in_progress = true;
+	}
+
+	/* Track how many CPUs have entered LFA_ACTIVATE for this round. */
+	activation_users += 1U;
+
+	return LFA_SUCCESS;
+}
+
+
+static void lfa_activate_finish(uint32_t component_id, bool activation_complete)
+{
+	if (activation_users > 0U) {
+		activation_users -= 1U;
+	}
+
+	if (!activation_complete) {
+		return;
+	}
+
+	if (activation_users == 0U) {
+		activation_in_progress = false;
+		activation_skip_cpu_rendezvous = false;
+		if (!activation_failed) {
+			lfa_components[component_id].activation_pending = false;
+		}
+	}
+}
+
 uint64_t lfa_smc_handler(uint32_t smc_fid, u_register_t x1, u_register_t x2,
 			 u_register_t x3, u_register_t x4, void *cookie,
 			 void *handle, u_register_t flags)
@@ -362,9 +435,92 @@ uint64_t lfa_smc_handler(uint32_t smc_fid, u_register_t x1, u_register_t x2,
 		break;
 
 	case LFA_ACTIVATE:
-		ret = lfa_activate(fw_seq_id, x2, x3, x4);
-		/* TODO: implement activate again */
-		SMC_RET2(handle, ret, 0ULL);
+		/* LFA_ACTIVATE flow:
+		 * - LFA_SKIP_CPU_RENDEZVOUS_BIT controls skip request on entry.
+		 * - Serialize with lfa_lock, but never block behind a
+		 *   skip-rendezvous activation.
+		 * - lfa_activate_prepare() validates state, selects activator,
+		 *   and latches policy.
+		 * - The first CPU decides rendezvous policy for the whole
+		 *   activation.
+		 * - Skip rendezvous keeps the lock for the full activation;
+		 *   normal path releases it.
+		 * - activator->activate() may return -EAGAIN, mapped to
+		 *   LFA_CALL_AGAIN in lfa_flags.
+		 * - lfa_activate_finish() updates bookkeeping and clears
+		 *   in-progress state when done.
+		 */
+		bool hold_lock = false;
+		bool activation_complete = true;
+		struct lfa_component_ops *activator;
+		/* Caller request: skip CPU rendezvous for this activation. */
+		bool skip_cpu_rendezvous =
+			((x2 & LFA_SKIP_CPU_RENDEZVOUS_BIT) != 0U);
+
+		/*
+		 * When skip_cpu_rendezvous=1 (or when a skip rendezvous
+		 * activation is already in progress), concurrent LFA_ACTIVATE
+		 * calls must not be accepted; return LFA_BUSY instead of
+		 * blocking.
+		 */
+		if (skip_cpu_rendezvous) {
+			/* Non-blocking serialization for skip rendezvous requests. */
+			if (!spin_trylock(&lfa_lock)) {
+				SMC_RET1(handle, LFA_BUSY);
+			}
+		} else {
+			/*
+			 * Normal path: take the lock, but reject if a skip
+			 * activation is in progress.
+			 */
+			spin_lock(&lfa_lock);
+			if (activation_skip_cpu_rendezvous) {
+				spin_unlock(&lfa_lock);
+				SMC_RET1(handle, LFA_BUSY);
+			}
+		}
+
+		ret = lfa_activate_prepare(fw_seq_id, x2, &activator);
+		hold_lock = (ret == LFA_SUCCESS) && activation_skip_cpu_rendezvous;
+
+		/*
+		 * Keep the lock held for the full activation only when skip
+		 * rendezvous is in effect.
+		 */
+		if (!hold_lock) {
+			spin_unlock(&lfa_lock);
+		}
+
+		if (ret != LFA_SUCCESS) {
+			SMC_RET2(handle, ret, 0ULL);
+		}
+
+		if (activator->activate != NULL) {
+			ret = activator->activate(&current_activation, x3, x4);
+		}
+
+		/* Reacquire lock before updating shared activation state. */
+		if (!hold_lock) {
+			spin_lock(&lfa_lock);
+		}
+
+		lfa_flags = 0ULL;
+		if (ret == -EAGAIN) {
+			/* Multi-stage activation: caller must reissue LFA_ACTIVATE. */
+			ret = LFA_SUCCESS;
+			lfa_flags = LFA_CALL_AGAIN;
+			activation_complete = false;
+		} else if (ret != LFA_SUCCESS) {
+			activation_failed = true;
+		}
+
+		/* Update activation bookkeeping and clear in-progress state if complete. */
+		lfa_activate_finish(fw_seq_id, activation_complete);
+
+		spin_unlock(&lfa_lock);
+
+		SMC_RET2(handle, ret, lfa_flags);
+
 		break;
 
 	case LFA_CANCEL: