vgsp: m169b bounded device-dst guard (3s per destination page, then release with the walk translation; r173: the unbounded guard deadlocked mail's first H2D - device pins only appear via the launch/fill paths, which the held copy blocked)

1 files changed, 56 insertions, 1 deletions

diff --git a/kernel/gsp_sema_service.c b/kernel/gsp_sema_service.c
index 343684b..93bcd20 100644
--- a/kernel/gsp_sema_service.c
+++ b/kernel/gsp_sema_service.c
@@ -731,6 +731,8 @@ struct sema_svc {
 	u64			copy_watch_log;		/* sema_copy_watch log budget */
 	u64			copy_dst_hold;		/* m169: device-dst copies held for
 						 * want of a pin (stale-table guard) */
+	u64			copy_dst_relaxed;	/* m169b: guards released without
+						 * a pin after the bounded wait */
 	u64			copy_pat_log;		/* sema_copy_pat log budget */
 	u64			copy_dst_log;		/* sema_copy_dst log budget */
 	u32			op_tr_src;		/* provenance of last svc_op_translate */
@@ -2863,6 +2865,7 @@ static inline bool svc_pool_pa_identity(u64 va, u64 pa)
 }
 
 static void svc_pool_boot_store(u64 va, u64 pa, int ap);	/* m168 */
+static bool svc_dst_guard_hold(u64 va);			/* m169b */
 
 static int svc_pool_pa_lookup(u64 va, u64 *pa, int *ap)
 {
@@ -4573,7 +4576,8 @@ static int svc_copy(struct nv_vgpu_device *vgpu, u64 dst, u64 src, size_t total,
 	 */
 	if (dst_virt && dst_aperture == CE_APERTURE_VID &&
 	    dst_prov >= 3 && dst_orig >= SVC_VAS_FLOOR &&
-	    gsp_sema_copy_dst_pin_guard) {
+	    gsp_sema_copy_dst_pin_guard &&
+	    svc_dst_guard_hold(dst_orig)) {
 		svc.copy_dst_hold++;
 		if (svc.copy_dst_hold <= 16)
 			pr_info("sema-svc: device-dst copy held: dst=0x%llx prov=%u (no pin yet; stale-table guard)\n",
@@ -9637,6 +9641,57 @@ bool gsp_sema_pool_hold_fresh = 1;
 bool gsp_sema_copy_dst_pin_guard = 1;
 
 /*
+ * m169b: the guard above must never deadlock the boot's first client. The
+ * first device-destination H2D of a client runs before any launch, and the
+ * pins for device VAs are (re)discovered by the launch/fill paths - so at
+ * that instant NO pin can exist. r173: mail's H2D was held forever
+ * (opdef_held ~6000 passes, six expiry cycles, the entry re-held on every
+ * re-decode because the retry keeps resolving prov>=3). Bound the wait per
+ * destination page: after this many ms the guard releases and the copy runs
+ * with the walk translation (the historical behavior; the walk of a
+ * just-built client table is fresh), logged loudly.
+ */
+unsigned gsp_sema_copy_dst_guard_ms = 3000;
+#define SVC_DST_GUARD_SLOTS	16
+struct svc_dst_guard {
+	u64		va_page;
+	unsigned long	first;
+};
+static struct svc_dst_guard svc_dst_guard[SVC_DST_GUARD_SLOTS];
+static u32 svc_dst_guard_next;
+
+/* true = the guard may hold this destination; false = release it. */
+static bool svc_dst_guard_hold(u64 va)
+{
+	u64 page = va & ~(u64)(SEMA_PAGE_SIZE - 1);
+	unsigned long now = jiffies;
+	u32 i, slot = SVC_DST_GUARD_SLOTS;
+
+	for (i = 0; i < SVC_DST_GUARD_SLOTS; i++) {
+		if (svc_dst_guard[i].va_page == page) {
+			if (time_before(now, svc_dst_guard[i].first +
+					msecs_to_jiffies(
+						gsp_sema_copy_dst_guard_ms)))
+				return true;
+			if (svc_dst_guard[i].first) {
+				svc_dst_guard[i].first = 0;
+				svc.copy_dst_relaxed++;
+				pr_info("sema-svc: device-dst guard released without a pin va=0x%llx (using the walk translation)\n",
+					page);
+			}
+			return false;
+		}
+		if (!svc_dst_guard[i].va_page)
+			slot = i;
+	}
+	if (slot == SVC_DST_GUARD_SLOTS)
+		slot = svc_dst_guard_next++ % SVC_DST_GUARD_SLOTS;
+	svc_dst_guard[slot].va_page = page;
+	svc_dst_guard[slot].first = now;
+	return true;
+}
+
+/*
  * CE release fallback: when a push carrying a tracking-semaphore release
  * cannot be read (and the content rescue failed), advance the channel's
  * tracking semaphore to the expected payload directly. The push's data