From: joshua stein <jcs@jcs.org>
Subject: Re: nvme: use I/O submission queue entry size reported by controller
To: tech@openbsd.org
Date: Fri, 29 May 2026 16:04:06 -0500

On Thu, 28 May 2026 at 23:48:27 +0200, Mark Kettenis wrote:
> > 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.

Because of course it does.  Well done, Apple.

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() */
>