From f0c8fd4ab843920e00065702c34bb383b02c601c Mon Sep 17 00:00:00 2001
From: Arthur Hanson Rasmusson <arthur@vgpu.io>
Date: Fri, 16 Oct 2026 17:07:19 -0400
Subject: vgsp: m162: retirement wait accepts partial writes only after 300 ms
 of stability (1024-page outputs were copied out with 2 pages written) + m161
 fetch-witness logging

---
 kernel/gsp_phys_booter.c | 66 +++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 65 insertions(+), 1 deletion(-)

diff --git a/kernel/gsp_phys_booter.c b/kernel/gsp_phys_booter.c
index 009eb4f..f54a0dc 100644
--- a/kernel/gsp_phys_booter.c
+++ b/kernel/gsp_phys_booter.c
@@ -17083,7 +17083,17 @@ gsp_phys_gr_output_retire_wait(const struct gsp_phys_gr_submit *req,
 			why = "";
 			break;
 		}
-		if (changed > 0 && changed == prev && iter >= 3u) {
+		/*
+		 * m162: a partial count must be stable for ~300 ms before it
+		 * counts as settled. The old 3-iteration (~18 ms) window
+		 * accepted a stalled store ramp or an un-dispatched grid as
+		 * "settled": observed 1024-page vecadd outputs copied out with
+		 * only 2 pages written (the client then verified 32736 bad
+		 * elements). A genuinely masked/short kernel costs at most
+		 * 300 ms extra; a ramping engine gets the time its stores
+		 * need.
+		 */
+		if (changed > 0 && changed == prev && iter >= 60u) {
 			why = " (settled)";
 			break;
 		}
@@ -17099,6 +17109,24 @@ gsp_phys_gr_output_retire_wait(const struct gsp_phys_gr_submit *req,
 	return changed;
 }
 
+/*
+ * m161: hardware fetch witness. The host writes GSP_PHYS_GR_QMD_SENTINEL
+ * into the inline-QMD page before every deposit; the engine's QMD fetch is
+ * the only actor that overwrites it (the post-mortem has used this as its
+ * ran/not-run marker since m110). Computing it as a standalone check lets
+ * the outcome-retry path classify a zero-write result beyond the release
+ * word, which the sema service's pending-release sweep can satisfy in
+ * software.
+ */
+static bool gsp_phys_gr_qmd_fetched(const u8 *qmd_mem)
+{
+	if (!qmd_mem)
+		return false;
+	return get_unaligned_le32(qmd_mem +
+				  GSP_PHYS_GR_QMD_SENTINEL_WORD * 4) !=
+	       GSP_PHYS_GR_QMD_SENTINEL;
+}
+
 /*
  * m153: fill the bounce window from the request's guest pages and capture a
  * per-page checksum baseline. Used before the first publish and again before
@@ -18605,6 +18633,13 @@ gr_page_unmapped:
 	if (req->n_data && gsp_phys_gr_data_chunk()->pages) {
 		u32 wrote = gsp_phys_gr_output_retire_wait(req, bounce_csum_in);
 
+		if (wrote == 0) {
+			bool ff = gsp_phys_gr_qmd_fetched(qmd_dst_mem);
+
+			pr_info("vgsp-gr: first-attempt witness: engine fetch %s (qmd sentinel %s)\n",
+				ff ? "OK" : "NONE",
+				ff ? "overwritten" : "intact");
+		}
 		if (gsp_phys_rmcall_gr_nowrite_retry_value()) {
 			while (attempts < GSP_PHYS_RMCALL_GR_ATTEMPTS) {
 				if (wrote > 0)
@@ -18764,6 +18799,35 @@ gr_page_unmapped:
 						jiffies_to_msecs(jiffies -
 								 ack_start));
 				}
+				/*
+				 * m161: hardware fetch witness. The fresh-ack
+				 * poll cannot distinguish the engine's release
+				 * from the sema service's software release (its
+				 * pending-release sweep re-applies the payload
+				 * as soon as the word reads below it). The QMD
+				 * page's sentinel word is written only by the
+				 * engine's QMD fetch, so it is the one side
+				 * effect the sweep cannot fake: intact after the
+				 * wait = this deposit never reached the engine.
+				 */
+				if (qmd_dst_mem) {
+					unsigned long wdl = jiffies +
+						msecs_to_jiffies(1500);
+					bool fetched = false;
+
+					while (time_before(jiffies, wdl)) {
+						if (gsp_phys_gr_qmd_fetched(
+								qmd_dst_mem)) {
+							fetched = true;
+							break;
+						}
+						msleep(5);
+					}
+					pr_info("vgsp-gr: outcome retry %u: engine fetch witness %s (qmd sentinel %s)\n",
+						attempts,
+						fetched ? "OK" : "NONE",
+						fetched ? "overwritten" : "intact");
+				}
 				wrote = gsp_phys_gr_output_retire_wait(
 					req, bounce_csum_in);
 				pr_info("vgsp-gr: outcome retry %u done: engine wrote %u page(s)\n",
-- 
cgit v1.2.3