A recent report on bugs@ showed the nvme interrupt handler crashing
during reboot.  It's a bit weird that the nvme controller raises an
interrupt after we shut it down, but we shouldn't crash if that
happens.

The problem here is that we delete the IO queue and free the memory
used for it, but the interrupt handler unconditionally tries to process
it.  This diff just skips the IO queue if we've deleted it.  The
bug reporter has confirmed that this fixes it for them.

ok?


Index: nvme.c
===================================================================
RCS file: /cvs/src/sys/dev/ic/nvme.c,v
diff -u -p -r1.126 nvme.c
--- nvme.c	14 Jan 2026 01:07:57 -0000	1.126
+++ nvme.c	4 Feb 2026 04:45:59 -0000
@@ -557,6 +574,7 @@ nvme_shutdown(struct nvme_softc *sc)
 		printf("%s: unable to delete q, disabling\n", DEVNAME(sc));
 		goto disable;
 	}
+	sc->sc_q = NULL;
 
 	cc = nvme_read4(sc, NVME_CC);
 	CLR(cc, NVME_CC_SHN_MASK);
@@ -1574,7 +1593,7 @@ nvme_intr(void *xsc)
 	struct nvme_softc *sc = xsc;
 	int rv = 0;
 
-	if (nvme_q_complete(sc, sc->sc_q))
+	if (sc->sc_q != NULL && nvme_q_complete(sc, sc->sc_q))
 		rv = 1;
 	if (nvme_q_complete(sc, sc->sc_admin_q))
 		rv = 1;