vgsp: fail4 r234 - A-TRACE end-to-end 64KB copy trace + RDW rec-dump arming line

r233: the probe ran (attempt-1 completes now) with the same deterministic
foreign readback, while REC-DUMP/READ-DIVERGE-WIT/READ-ORDER-WIT/ledger
DIVERGE were all absent from the capture. The r231/r233 rings only cover
the transformer_mt window (6-7 GRID-WITs, 15 sema-bigcopy lines, all of
the transformer); the probe's launches are outside the saved ring, so the
witness absence is not yet attributable to the code. Two additions make
the next capture self-contained:

- RDW nrecs=<n> launch_va=<push>: one arming line per forwarded launch
  (budget 256) - a capture can never confuse 'witness did not run' with
  'no recs'; probe-class launches must show nrecs>0.

- A-TRACE, four labeled points for every 64 KB copy and every small
  launch (budgets 128/128):
    pt=P1  H2D source read (src_int4 as ints; expect 0 1 2 3)
    pt=P2  H2D destination right after the copy (dst_int4_after)
    pt=P3  engine-read point: for <=64-rec launches, the first recs'
           source-page content the copy-in stages (w0..15 per rec)
    pt=P4  D2H source read (the engine-authored page as ints)
    pt=P4R D2H host-side readback after the copy
  The probe A buffer is ints 0..16383; the first point where the pattern
  breaks is the bug site.

Stats check for the elision class: r231's probe-window stats show
copy_skipped=0 copy_soft=0 copy_fail=0 and no device-dst guard lines, so
no forwarded/skip elision is in play in that window; the trace decides
where the read/write split actually occurs.

Build green.

(cherry picked from commit 98bfc75410b214f7de3dfc6ef80bff76118ff14d)

1 files changed, 44 insertions, 0 deletions

diff --git a/kernel/gsp_sema_service.c b/kernel/gsp_sema_service.c
index d9f5895..b7290d4 100644
--- a/kernel/gsp_sema_service.c
+++ b/kernel/gsp_sema_service.c
@@ -3136,6 +3136,7 @@ static void svc_pool_boot_store(u64 va, u64 pa, int ap);	/* m168 */
 static bool svc_dst_guard_hold(u64 va);			/* m169b */
 static bool svc_dst_guard_pending(u64 va);		/* r231 */
 static u32 svc_read_order_log;				/* r231 budget */
+static u32 svc_atrace_log;				/* r234 A-TRACE budget */
 
 static int svc_pool_pa_lookup(u64 va, u64 *pa, int *ap)
 {
@@ -5368,6 +5369,31 @@ static int svc_copy(struct nv_vgpu_device *vgpu, u64 dst, u64 src, size_t total,
 			total);
 		pr_info("sema-bigcopy: src16=%16phN dst16_before=%16phN\n",
 			sb, db);
+		/*
+		 * r234 A-TRACE: one labeled line per 64 KB copy so the probe A
+		 * upload/readback is greppable end-to-end. pt=P1 = H2D source
+		 * read (the uploaded bytes as ints), pt=P4 = D2H source read
+		 * (the engine-authored page as ints). The expected content is
+		 * ints 0,1,2,3,... for the probe A buffer.
+		 */
+		if (total == 65536u && svc_atrace_log < 128u) {
+			u32 i0, i1, i2, i3, j0 = 0, j1 = 0, j2 = 0, j3 = 0;
+
+			svc_atrace_log++;
+			memcpy(&i0, sb, 4);
+			memcpy(&i1, sb + 4, 4);
+			memcpy(&i2, sb + 8, 4);
+			memcpy(&i3, sb + 12, 4);
+			memcpy(&j0, db, 4);
+			memcpy(&j1, db + 4, 4);
+			memcpy(&j2, db + 8, 4);
+			memcpy(&j3, db + 12, 4);
+			pr_info("vgsp: A-TRACE pt=%s dst_va=0x%llx dst_pa=0x%llx dst_prov=%u | src_va=0x%llx src_pa=0x%llx src_prov=%u | src_int4=%d %d %d %d dst_int4_before=%d %d %d %d\n",
+				dst_shadow || dst_aperture == CE_APERTURE_VID ?
+				"P1" : "P4",
+				dst_orig, dst, dst_prov, src_orig, src,
+				src_prov, i0, i1, i2, i3, j0, j1, j2, j3);
+		}
 	}
 
 	/*
@@ -5738,6 +5764,24 @@ static int svc_copy(struct nv_vgpu_device *vgpu, u64 dst, u64 src, size_t total,
 		}
 		pr_info("sema-bigcopy: dst16_after=%16phN (dst_va=0x%llx pa=0x%llx)\n",
 			da, dst_orig, dst);
+		/*
+		 * r234 A-TRACE pt=P2/P4R: the destination content right after
+		 * the copy - for H2D this is the landed upload (P2), for D2H
+		 * the host-side readback result (P4R).
+		 */
+		if (total == 65536u && svc_atrace_log < 128u) {
+			u32 i0, i1, i2, i3;
+
+			svc_atrace_log++;
+			memcpy(&i0, da, 4);
+			memcpy(&i1, da + 4, 4);
+			memcpy(&i2, da + 8, 4);
+			memcpy(&i3, da + 12, 4);
+			pr_info("vgsp: A-TRACE pt=%s dst_va=0x%llx dst_pa=0x%llx dst_int4_after=%d %d %d %d\n",
+				dst_shadow || dst_aperture == CE_APERTURE_VID ?
+				"P2" : "P4R",
+				dst_orig, dst, i0, i1, i2, i3);
+		}
 	}
 
 	if (gsp_sema_dbg && !src_shadow && !dst_shadow &&