vgsp r580: walk-over-bootcache for pool pages + event burst dedup and fast-path hint

Pool resolution (thread: the starve wedge surviving the r577 fix): the
boot-scoped pool cache survives session flushes, but a pool page MOVES
between sessions and the old page often stays readable, so the read-back
proof cannot tell - the resolver wrote releases to the stale cache PA while
the client's tracker read its current page. Live evidence (r579 boot):
pool-wr src=bootcache pa=0x11e6d9000 for va=0x121000000 while the injected
pin/current page was pa=0x134730000; the client spun in uvm_tracker_wait
for minutes. svc_pool_pa_resolve now tries the structural walk (the
client's own page tables) BEFORE trusting the cache: a differing,
read-proven walk page wins (src=walk-over-boot) and the cached page is kept
as the fan-out secondary.

Event burst (r579 boot: events_dropped=724, the 'no postable event
(events_n=8 dropped=724)' sentinel every 0.5 s): apply the 250 ms per-event
dedup to the per-completion shotgun (8 records per completion burned the
48/s budget), and hoist the completion hint above the pump fast path so it
runs under load too (a dropped wake is re-posted within 0.5 s).

1 files changed, 14 insertions, 0 deletions

diff --git a/kernel/gsp_rm_emulation.c b/kernel/gsp_rm_emulation.c
index fb0f31d..2a957b3 100644
--- a/kernel/gsp_rm_emulation.c
+++ b/kernel/gsp_rm_emulation.c
@@ -882,6 +882,20 @@ int gsp_rm_post_channel_event(struct nv_vgpu_device *vgpu, u32 h_src)
 		for (i = 0; i < rm->events_n; i++) {
 			if (!rm->events[i].valid)
 				continue;
+			/*
+			 * r580: apply the hint dedup to the per-completion
+			 * shotgun. Every completion posts ALL registered
+			 * events (the ABI gives no source association), so a
+			 * completion burst burns the burst budget 8 records
+			 * per completion and real wake-ups get dropped
+			 * (r579 boot: events_dropped=724). A redundant
+			 * re-post within 250 ms adds no wake-up - the
+			 * client's dispatcher re-reads channel state on any
+			 * event - and the 0.5 s hint re-posts late waiters.
+			 */
+			if (time_before(jiffies, rm->events[i].last_post +
+					GSPRM_EVENT_HINT_DEDUP))
+				continue;
 			gsp_rm_fill_ev_payload(rm, i, payload);
 			{
 				int rc = gsp_rm_send_flags(ctx,