From ae2bd4def95997ff7198b1bad21a73a267eea604 Mon Sep 17 00:00:00 2001
From: Arthur Hanson Rasmusson <arthur@vgpu.io>
Date: Sat, 26 Sep 2026 02:46:41 -0400
Subject: kernel: add a channel-table dump param; tools: fix memprobe --max
 parsing

---
 kernel/gsp_sema_service.c | 69 +++++++++++++++++++++++++++++++++++++++++++++++
 kernel/gsp_sema_service.h |  1 +
 kernel/main.c             | 17 ++++++++++++
 3 files changed, 87 insertions(+)

(limited to 'kernel')

diff --git a/kernel/gsp_sema_service.c b/kernel/gsp_sema_service.c
index ffc8ae2..1f1222e 100644
--- a/kernel/gsp_sema_service.c
+++ b/kernel/gsp_sema_service.c
@@ -3121,6 +3121,74 @@ int gsp_sema_service_probe(u64 gpu_va, u32 count)
 	return 0;
 }
 
+/*
+ * Diagnostic dump of the service's channel table: GPFIFO/USERD state, the
+ * pending-entry expectation and the two NvNotification slots the client polls
+ * (status + info32). Runs in the service thread (guest-DMA reads need a
+ * kthread context); the sysfs writer waits for completion.
+ */
+static struct completion chan_dump_done;
+static bool chan_dump_pending;
+
+static void svc_handle_chan_dump(struct nv_vgpu_device *vgpu)
+{
+	struct svc_channel local[SVC_MAX_CHANNELS];
+	unsigned long flags;
+	int i, n = 0;
+
+	if (!chan_dump_pending)
+		return;
+
+	spin_lock_irqsave(&svc.chan_lock, flags);
+	for (i = 0; i < SVC_MAX_CHANNELS; i++)
+		if (svc.chan[i].valid)
+			local[n++] = svc.chan[i];
+	spin_unlock_irqrestore(&svc.chan_lock, flags);
+
+	pr_info("sema-chan-dump: %d channel(s)\n", n);
+	for (i = 0; i < n; i++) {
+		struct svc_channel *ch = &local[i];
+		u32 st0 = 0, st1 = 0, info0 = 0, info1 = 0;
+
+		if (ch->notifier_pa) {
+			svc_read_ap(vgpu, ch->notifier_pa + 14,
+				    ch->notifier_as, &st0, 2);
+			svc_read_ap(vgpu, ch->notifier_pa + 8,
+				    ch->notifier_as, &info0, 4);
+			svc_read_ap(vgpu, ch->notifier_pa + 16 + 14,
+				    ch->notifier_as, &st1, 2);
+			svc_read_ap(vgpu, ch->notifier_pa + 16 + 8,
+				    ch->notifier_as, &info1, 4);
+		}
+		pr_info("sema-chan-dump: h=0x%x eng=%u gpfifo=0x%llx ent=%u userd=0x%llx as=%u ok=%d get=%u sub=%llu exp=%u notif=0x%llx as=%u slot0{info=0x%x st=0x%x} slot1{info=0x%x st=0x%x} notified=%llu\n",
+			ch->h_object, ch->engine_type, ch->gpfifo_va,
+			ch->gpfifo_entries, ch->userd_pa, ch->userd_as,
+			ch->userd_ok, ch->last_get, ch->submissions,
+			ch->expected_sem_payload, ch->notifier_pa,
+			ch->notifier_as, info0, st0, info1, st1,
+			ch->notified);
+	}
+
+	chan_dump_pending = false;
+	complete(&chan_dump_done);
+}
+
+int gsp_sema_service_dump_channels(void)
+{
+	if (!svc.task)
+		return -ENODEV;
+
+	init_completion(&chan_dump_done);
+	chan_dump_pending = true;
+
+	if (!wait_for_completion_timeout(&chan_dump_done, 3 * HZ)) {
+		chan_dump_pending = false;
+		return -ETIMEDOUT;
+	}
+	return 0;
+}
+
+
 /*
  * Debug injection: teach the service one {GPU VA -> guest PA} translation.
  * Some client mappings (user VA == GPU VA, sysmem backed) are not
@@ -3205,6 +3273,7 @@ static int svc_thread(void *arg)
 
 		svc_handle_probe(vgpu);
 		svc_handle_map_add();
+		svc_handle_chan_dump(vgpu);
 
 		if (!svc.direct_base ||
 		    time_after(jiffies, svc.last_build + 10 * HZ))
diff --git a/kernel/gsp_sema_service.h b/kernel/gsp_sema_service.h
index 6b8dc6a..d5e41a6 100644
--- a/kernel/gsp_sema_service.h
+++ b/kernel/gsp_sema_service.h
@@ -57,6 +57,7 @@ void gsp_sema_service_vaspace_del(u32 h_vaspace);
 int  gsp_sema_service_start(void);
 void gsp_sema_service_stop(void);
 int  gsp_sema_service_probe(u64 gpu_va, u32 count);
+int  gsp_sema_service_dump_channels(void);
 int  gsp_sema_service_add_map(u64 gpu_va, u64 pa, u64 len, u32 ap);
 void gsp_sema_service_doorbell(u32 token);
 
diff --git a/kernel/main.c b/kernel/main.c
index 63657f3..f23be27 100644
--- a/kernel/main.c
+++ b/kernel/main.c
@@ -2247,6 +2247,23 @@ static const struct kernel_param_ops nv_vgpu_sema_probe_ops = {
 module_param_cb(sema_probe, &nv_vgpu_sema_probe_ops, NULL, 0200);
 MODULE_PARM_DESC(sema_probe, "Dump sema-service map + slot values for a GPU VA");
 
+/*
+ * Debug: dump the semaphore service's channel table (GPFIFO/USERD state and
+ * the two NvNotification slots each channel exposes):
+ *   echo 1 > .../parameters/chan_dump
+ */
+static int nv_vgpu_chan_dump_set(const char *val, const struct kernel_param *kp)
+{
+	return gsp_sema_service_dump_channels();
+}
+
+static const struct kernel_param_ops nv_vgpu_chan_dump_ops = {
+	.set = nv_vgpu_chan_dump_set,
+};
+
+module_param_cb(chan_dump, &nv_vgpu_chan_dump_ops, NULL, 0200);
+MODULE_PARM_DESC(chan_dump, "Dump the sema service channel table (any value)");
+
 /*
  * Debug: inject a verified {GPU VA -> guest PA} translation into the
  * semaphore service (used when the client's mapping cannot be discovered
-- 
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