From fc9a0840231770bc7e7dcfe4616babdc6d4389a6 Mon Sep 17 00:00:00 2001
From: Warner Losh <imp@FreeBSD.org>
Date: Thu, 15 Jul 2021 16:17:23 -0600
Subject: [PATCH] nvme: Enable interrupts after qpair fully constructed

To guard against the ill effects of a spurious interrupt during
construction (or one that was bogusly pending), enable interrupts after
the qpair is completely constructed. Otherwise, we can die with null
pointer dereferences in nvme_qpair_process_completions. This has been
observed in at least one pre-release NVMe drive where the MSIX interrupt
fired while the queue was being created, before we'd started the NVMe
controller card.

The alternative of only turning on the interrupts after the rest was
tried, but was insufficient to work around this bug and made the code
more complicated w/o benefit.

Reviewed by:		mav, chuck
Sponsored by:		Netflix
Differential Revision:	https://reviews.freebsd.org/D31182
---
 sys/dev/nvme/nvme_qpair.c | 49 ++++++++++++++++++++-------------------
 1 file changed, 25 insertions(+), 24 deletions(-)

diff --git a/sys/dev/nvme/nvme_qpair.c b/sys/dev/nvme/nvme_qpair.c
index 12770f38d42e..4402d1000e67 100644
--- a/sys/dev/nvme/nvme_qpair.c
+++ b/sys/dev/nvme/nvme_qpair.c
@@ -675,30 +675,6 @@ nvme_qpair_construct(struct nvme_qpair *qpair,
 	qpair->num_trackers = num_trackers;
 	qpair->ctrlr = ctrlr;
 
-	if (ctrlr->msix_enabled) {
-		/*
-		 * MSI-X vector resource IDs start at 1, so we add one to
-		 *  the queue's vector to get the corresponding rid to use.
-		 */
-		qpair->rid = qpair->vector + 1;
-
-		qpair->res = bus_alloc_resource_any(ctrlr->dev, SYS_RES_IRQ,
-		    &qpair->rid, RF_ACTIVE);
-		if (bus_setup_intr(ctrlr->dev, qpair->res,
-		    INTR_TYPE_MISC | INTR_MPSAFE, NULL,
-		    nvme_qpair_msix_handler, qpair, &qpair->tag) != 0) {
-			nvme_printf(ctrlr, "unable to setup intx handler\n");
-			goto out;
-		}
-		if (qpair->id == 0) {
-			bus_describe_intr(ctrlr->dev, qpair->res, qpair->tag,
-			    "admin");
-		} else {
-			bus_describe_intr(ctrlr->dev, qpair->res, qpair->tag,
-			    "io%d", qpair->id - 1);
-		}
-	}
-
 	mtx_init(&qpair->lock, "nvme qpair lock", NULL, MTX_DEF);
 
 	/* Note: NVMe PRP format is restricted to 4-byte alignment. */
@@ -818,6 +794,31 @@ nvme_qpair_construct(struct nvme_qpair *qpair,
 	qpair->act_tr = malloc_domainset(sizeof(struct nvme_tracker *) *
 	    qpair->num_entries, M_NVME, DOMAINSET_PREF(qpair->domain),
 	    M_ZERO | M_WAITOK);
+
+	if (ctrlr->msix_enabled) {
+		/*
+		 * MSI-X vector resource IDs start at 1, so we add one to
+		 *  the queue's vector to get the corresponding rid to use.
+		 */
+		qpair->rid = qpair->vector + 1;
+
+		qpair->res = bus_alloc_resource_any(ctrlr->dev, SYS_RES_IRQ,
+		    &qpair->rid, RF_ACTIVE);
+		if (bus_setup_intr(ctrlr->dev, qpair->res,
+		    INTR_TYPE_MISC | INTR_MPSAFE, NULL,
+		    nvme_qpair_msix_handler, qpair, &qpair->tag) != 0) {
+			nvme_printf(ctrlr, "unable to setup intx handler\n");
+			goto out;
+		}
+		if (qpair->id == 0) {
+			bus_describe_intr(ctrlr->dev, qpair->res, qpair->tag,
+			    "admin");
+		} else {
+			bus_describe_intr(ctrlr->dev, qpair->res, qpair->tag,
+			    "io%d", qpair->id - 1);
+		}
+	}
+
 	return (0);
 
 out: