gsp-phys: P6b waves 1.5 and 2 - deferred release and hardware-authored guest copies

- new default-off gsp_phys_work_defer_release: a forwarded guest push's
  releases are recorded and its GPFIFO entry is held (no consume, no
  GP_GET write, no counter publish/stall) until the work item publishes
  completion; the service thread then delivers the releases, with a
  fallback on failure/timeout (500 ms cap enforced every pump pass)/
  pause/quiesce/channel-delete
- new default-off gsp_phys_work_hw_primary: the software copy is skipped
  for forwarded ops, so the physical engine authors the data; a once-only
  software copy runs before the releases on any hardware failure or when
  the request cannot be queued
- release-apply helpers extracted; exactly-once latches; channel-delete
  and teardown handling; counters and a work_guard state line
- live: deferred-release run engaged=75 applied=75 timeouts=0 with the
  full smoke green; hardware-primary run req=100 ok=100 verify_ok=100
  fallback=0 copy_skipped=119 copy_fail=0, smoke ALL OK 64/64 (guest read
  data the engine authored), with 19 fail-closed inline software
  fallbacks under single-inflight contention; a range-unregistered run
  proved the fallback (121 skipped copies, all recovered, smoke green)
- defaults off; the software path and all existing guards unchanged

1 files changed, 29 insertions, 0 deletions

diff --git a/kernel/gsp_phys_booter.c b/kernel/gsp_phys_booter.c
index 90a0a27..69a749a 100644
--- a/kernel/gsp_phys_booter.c
+++ b/kernel/gsp_phys_booter.c
@@ -7596,6 +7596,35 @@ static int gsp_phys_state_show(struct seq_file *m, void *v)
 				   GSP_PHYS_RMCALL_GUEST_PT_LINES_PER_PAGE);
 	}
 	{
+		/*
+		 * P6b wave-1.5/wave-2 deferred guest releases and copy
+		 * authorship: the sema service's held-release lifecycle plus
+		 * the deferral/hardware-primary parameter state. pending is the
+		 * current hold gauge (releases waiting on the forwarded copy);
+		 * copy_skipped is the withheld software copies, copy_soft/
+		 * copy_fail the service-thread fallback copies; the rest are
+		 * monotonic counters.
+		 */
+		u64 g_copy_skipped = 0, g_copy_soft = 0, g_copy_fail = 0;
+		u64 g_deferred = 0, g_applied = 0;
+		u64 g_fallback = 0, g_pending = 0, g_overflow = 0;
+		u64 g_engaged = 0, g_timeouts = 0, g_canceled = 0;
+
+		gsp_sema_service_fwd_hold_stats(&g_copy_skipped, &g_copy_soft,
+						&g_copy_fail, &g_deferred,
+						&g_applied, &g_fallback,
+						&g_pending, &g_overflow,
+						&g_engaged, &g_timeouts,
+						&g_canceled);
+		seq_printf(m,
+			   "work_guard: copy_skipped=%llu deferred=%llu applied=%llu fallback=%llu pending=%llu overflow=%llu engaged=%llu timeouts=%llu canceled=%llu defer_param=%u copy_soft=%llu copy_fail=%llu hw_primary_param=%u\n",
+			   g_copy_skipped, g_deferred, g_applied, g_fallback,
+			   g_pending, g_overflow, g_engaged, g_timeouts,
+			   g_canceled, gsp_phys_work_defer_release_enabled(),
+			   g_copy_soft, g_copy_fail,
+			   gsp_phys_work_hw_primary_enabled());
+	}
+	{
 		char guest_ram[512];
 
 		gsp_phys_guest_ram_state(guest_ram, sizeof(guest_ram));