vgsp-sema: ack the class-2d IMMD NOTIFY from the X DDX sync

The X server's nvFermiSync queues the class-2d completion as
IMMD_DATA methods (SET_NOTIFY_A/B + NOTIFY 0x10c WRITE_ONLY). The
run-shaped watchdog form was already handled; the IMMD form fell
into the default case, so the zeroed NvNotification was never
authored and the server spun in WAIT (0,8,0x8000,...) with the
status left IN_PROGRESS. Handle the IMMD form and treat the 0x8000
IN_PROGRESS status as armed in the keepalive scan. The mode-set
then completes and the 2D sync acks (verified on the emulated
vGPU: no WAIT, sema-notify2d zeroed). The A/B knob
sema_2d_notify_immd=0 restores the old dropped-NOTIFY behaviour.

1 files changed, 37 insertions, 1 deletions

diff --git a/kernel/gsp_sema_service.c b/kernel/gsp_sema_service.c
index e42e23d..6f0103b 100644
--- a/kernel/gsp_sema_service.c
+++ b/kernel/gsp_sema_service.c
@@ -18233,6 +18233,13 @@ static void svc_push_raw_dump(const u8 *buf, u32 len, u64 push_va,
 
 static u64 svc_notify2d_done;
 static u32 svc_notify2d_log;
+/*
+ * r1608 A/B: the X DDX's IMMD class-2d NOTIFY ack (the nvFermiSync
+ * completion). Enabled by default; set 0 to reproduce the pre-r1608
+ * dropped-NOTIFY behaviour (the Xorg mode-set WAIT) without a rebuild.
+ */
+static bool gsp_sema_2d_notify_immd = true;
+module_param_named(sema_2d_notify_immd, gsp_sema_2d_notify_immd, bool, 0644);
 
 static bool svc_notify2d_write(struct nv_vgpu_device *vgpu,
 			       struct svc_channel *ch, bool completion)
@@ -18509,6 +18516,29 @@ static void svc_twod_method(struct nv_vgpu_device *vgpu,
 	case 0x2ac:
 		tw->operation = v;
 		break;
+	/*
+	 * r1608: the X DDX's nvFermiSync (nvFermiXAASync) queues the
+	 * class-2d completion as IMMD_DATA methods: SET_NOTIFY_A/B name
+	 * the NvNotification VA and NOTIFY (0x10c, payload 0 =
+	 * WRITE_ONLY) must author the zeroed 16-byte notification. The
+	 * watchdog path below has handled the run-shaped form since r828;
+	 * the IMMD form previously fell into the default case and was
+	 * dropped, so the X server's post-selection 2D sync spun in
+	 * "NVIDIA(GPU-0): WAIT (0, 8, 0x8000, ...)" forever (the status
+	 * word stayed IN_PROGRESS 0x8000). The mode-set never completed,
+	 * glsStartServer/glsDeviceHandle never ran, and the GL client's
+	 * physical-device init (class/gpuGartSize/+0x18e0) stayed empty.
+	 */
+	case SVC_2D_SET_NOTIFY_A:
+		ch->notify2d_va = (u64)(v & 0x1ffffff) << 32;
+		break;
+	case SVC_2D_SET_NOTIFY_B:
+		ch->notify2d_va |= (u64)v;
+		break;
+	case SVC_2D_NOTIFY:
+		if (v == 0 && gsp_sema_2d_notify_immd)
+			svc_notify2d_write(vgpu, ch, true);
+		break;
 	case 0x2a0:
 		tw->rop = v;
 		break;
@@ -18622,7 +18652,13 @@ static void svc_notify2d_keepalive(struct nv_vgpu_device *vgpu,
 		u16 st;
 
 		memcpy(&st, slots + slot * 16 + 14, 2);
-		if (st != 0xffff)
+		/*
+		 * r1608: the 2D completion notifier is armed with
+		 * NV9097_NOTIFICATION_STATUS_IN_PROGRESS (0x8000) while the
+		 * GPU works on it (the X DDX's nvFermiSync waits for it to
+		 * become 0); the older watchdog slots use 0xffff. Ack both.
+		 */
+		if (st != 0xffff && !(st & 0x8000))
 			continue;	/* not armed - nothing to ack */
 		if (svc_write_ap(vgpu, ch->notifier_pa + slot * 16,
 				 ch->notifier_as, zero, sizeof(zero)))