vgsp-gl: bounded setup-push hold for maturity debugging

sema_gr_setup_hold_ms (default 0, clamp 2000 ms) holds/defer the draw
window while the 60216-byte setup push pin is landing, replacing the
~50% IMMATURE-SKIP lottery. Measured: 2000 ms stalls the ring behind
the unreadable 0x4021004 entry (8 launches then silence), so the
default stays 0; the param is a debug gate only. r1557 with hold=0
produced 64 beef launches and the DS A/B baseline
80000000->a0040a06. Evidence: Handoff cont 8.

1 files changed, 68 insertions, 5 deletions

diff --git a/kernel/gsp_sema_service.c b/kernel/gsp_sema_service.c
index 5348c95..dafbad6 100644
--- a/kernel/gsp_sema_service.c
+++ b/kernel/gsp_sema_service.c
@@ -26481,6 +26481,17 @@ unsigned gsp_sema_push_hold_ms = 2500;
  */
 unsigned gsp_sema_gr_setup_hold_ms;
 
+/*
+ * SESSION 155 CONT 8: per-boot draw-window hold deadline for the same
+ * parameter. While it is open, an immature beef window is busy-deferred
+ * (candidate survives, pump re-offers it) instead of being software-
+ * completed by IMMATURE-SKIP, so the pump keeps walking the held setup-push
+ * entry and a late pin/upload can still mature the capture. Armed once per
+ * module load (= per boot) and bounded by the clamped param (<= 2000 ms).
+ */
+static unsigned long svc_setup_hold_wait_j;
+static bool svc_setup_hold_exp_logged;
+
 static unsigned long svc_gr_ring_tried;	/* ranks that got a diagnostic line */
 
 /*
@@ -26610,14 +26621,26 @@ static void svc_gr_setup_hold_arm(struct svc_channel *ch, u64 va, u32 idx,
 		 */
 		svc_pushfail_log = 0;
 		svc_pinrej_log = 0;
-		if (gsp_sema_gr_setup_hold_ms)
+		/*
+		 * SESSION 155 CONT 8: the hold is hard-bounded at 2000 ms.
+		 * Longer values (the old r1083-r1087 20 s experiment) block
+		 * the whole ring behind the unreadable setup entry and derail
+		 * the client; 0 still disables the hold (demand rows remain).
+		 */
+		if (gsp_sema_gr_setup_hold_ms) {
+			unsigned hold_ms = min_t(unsigned,
+						 READ_ONCE(gsp_sema_gr_setup_hold_ms),
+						 2000u);
+
 			ch->gr_setup_hold_until = jiffies +
-				msecs_to_jiffies(gsp_sema_gr_setup_hold_ms);
-		else
+				msecs_to_jiffies(hold_ms);
+		} else {
 			ch->gr_setup_hold_until = 0;
-		pr_info("sema-chan: GR setup hold h=0x%x entry=%u va=0x%llx len=%u armed (demanding 4K pages; hold=%u ms; pending until the pin lands)\n",
+		}
+		pr_info("sema-chan: GR setup hold h=0x%x entry=%u va=0x%llx len=%u armed (demanding 4K pages; hold=%u ms clamped<=2000; pending until the pin lands)\n",
 			ch->h_object, idx, va, len,
-			gsp_sema_gr_setup_hold_ms);
+			ch->gr_setup_hold_until ?
+				jiffies_to_msecs(ch->gr_setup_hold_until - jiffies) : 0u);
 	}
 	for (poff = 0; poff < len && poff < 0x40000u; poff += SEMA_PAGE_SIZE) {
 		svc_log_stalled_va(page + poff);
@@ -36971,6 +36994,46 @@ static bool svc_gr_request(struct nv_vgpu_device *vgpu,
 	    (ch->h_object & 0xfffff000u) == 0xbeef0000u &&
 	    READ_ONCE(svc_mme_prelude_flag) &&
 	    !gsp_sema_mme_prelude_mature()) {
+		unsigned hold_ms =
+			min_t(unsigned, READ_ONCE(gsp_sema_gr_setup_hold_ms),
+			      2000u);
+
+		/*
+		 * SESSION 155 CONT 8: bounded setup-push draw-window hold.
+		 * Instead of immediately software-completing an immature
+		 * beef window, keep the candidate pending (busy-defer, no
+		 * bridge fallback) while a per-boot deadline of
+		 * sema_gr_setup_hold_ms (clamped <= 2000 ms) is open. The
+		 * pump re-offers the window on every pass and keeps walking
+		 * the held setup-push entry, so a pin/upload that lands
+		 * inside the window matures the capture and the next retry
+		 * forwards the client's real window. Past the deadline the
+		 * historical IMMATURE-SKIP resumes, one loud receipt.
+		 */
+		if (hold_ms && !svc_setup_hold_wait_j)
+			svc_setup_hold_wait_j = jiffies +
+				msecs_to_jiffies(hold_ms);
+		if (hold_ms && time_before(jiffies, svc_setup_hold_wait_j)) {
+			clear_bit_unlock(SVC_FWD_INFLIGHT, &svc_fwd_state);
+			mutex_unlock(&svc_fwd_lock);
+			svc_gr_busy_defer = true;
+			svc.fwd_gr_refused++;
+			svc_gr_prelude_gate_defer++;
+			if (svc_gr_prelude_gate_defer <= 24 ||
+			    (svc_gr_prelude_gate_defer & 0xFF) == 1)
+				pr_info("vgsp-work: SETUP-HOLD-DEFER h=0x%x push=0x%llx (MME prelude immature; holding the window for the setup pin, remaining=%u ms) n=%llu\n",
+					ch->h_object, svc_gr_cand.push_va,
+					jiffies_to_msecs(svc_setup_hold_wait_j -
+							 jiffies),
+					svc_gr_prelude_gate_defer);
+			return false;
+		}
+		if (hold_ms && !svc_setup_hold_exp_logged) {
+			svc_setup_hold_exp_logged = true;
+			pr_info("vgsp-work: SETUP-HOLD-EXPIRED h=0x%x push=0x%llx (hold=%u ms elapsed, prelude still immature; resuming IMMATURE-SKIP) n=%llu\n",
+				ch->h_object, svc_gr_cand.push_va, hold_ms,
+				svc_gr_prelude_gate_defer);
+		}
 		clear_bit_unlock(SVC_FWD_INFLIGHT, &svc_fwd_state);
 		mutex_unlock(&svc_fwd_lock);
 		svc.fwd_gr_refused++;