From: Mark Kettenis <mark.kettenis@xs4all.nl>
Subject: Re: nvme: use I/O submission queue entry size reported by controller
To: joshua stein <jcs@jcs.org>
Cc: tech@openbsd.org
Date: Thu, 28 May 2026 23:48:27 +0200

> Date: Sun, 17 May 2026 12:25:57 -0500
> From: joshua stein <jcs@jcs.org>
> 
> On at least the Apple T2 NVMe, 128-byte submission queue entries on
> I/O queues are required instead of the standard 64 bytes.
> 
> This gets NVMe working on the 2018 Mac Mini.  Also tested on a 
> non-Apple NVMe but more tests would be helpful.

Unfortunately this breaks the NVMe on my 2023 Mac mini.  It advertises
128-byte submission queue entries, but only works with 64-byte ones.

ok?


Index: dev/ic/nvme.c
===================================================================
RCS file: /cvs/src/sys/dev/ic/nvme.c,v
diff -u -p -r1.127 nvme.c
--- dev/ic/nvme.c	27 May 2026 15:04:14 -0000	1.127
+++ dev/ic/nvme.c	28 May 2026 21:37:35 -0000
@@ -1288,10 +1288,12 @@ nvme_identify(struct nvme_softc *sc, u_i
 
 	sc->sc_nn = lemtoh32(&identify->nn);
 
-	/* use maximum I/O SQE size reported */
-	sc->sc_sqe_size = 1 << (identify->sqes >> 4);
-	if (sc->sc_sqe_size < sizeof(struct nvme_sqe))
-		sc->sc_sqe_size = sizeof(struct nvme_sqe);
+	if (sc->sc_sqe_size == 0) {
+		/* use maximum I/O SQE size reported */
+		sc->sc_sqe_size = 1 << (identify->sqes >> 4);
+		if (sc->sc_sqe_size < sizeof(struct nvme_sqe))
+			sc->sc_sqe_size = sizeof(struct nvme_sqe);
+	}
 
 	/*
 	 * At least one Apple NVMe device presents a second, bogus disk that is
Index: arch/arm64/dev/aplns.c
===================================================================
RCS file: /cvs/src/sys/arch/arm64/dev/aplns.c,v
diff -u -p -r1.17 aplns.c
--- arch/arm64/dev/aplns.c	11 Jan 2026 12:47:48 -0000	1.17
+++ arch/arm64/dev/aplns.c	28 May 2026 21:37:35 -0000
@@ -234,6 +234,7 @@ nvme_ans_attach(struct device *parent, s
 	sc->sc_ios = faa->fa_reg[0].size;
 	sc->sc_ops = &nvme_ans_ops;
 	sc->sc_openings = 1;
+	sc->sc_sqe_size = sizeof(struct nvme_sqe);
 
 	if (nvme_attach(sc) != 0) {
 		/* error printed by nvme_attach() */