From: Mark Kettenis <mark.kettenis@xs4all.nl>
Subject: Re: em 64 bit dma
To: Alexander Bluhm <bluhm@openbsd.org>
Cc: tech@openbsd.org, kettenis@openbsd.org
Date: Tue, 03 Mar 2026 23:36:22 +0100

> Date: Tue, 3 Mar 2026 20:54:04 +0100
> From: Alexander Bluhm <bluhm@openbsd.org>
> Cc: Mark Kettenis <kettenis@openbsd.org>
> Content-Type: text/plain; charset=us-ascii
> Content-Disposition: inline
> 
> On Mon, Mar 02, 2026 at 08:22:31AM +0000, Vitaliy Makkoveev wrote:
> > > > > I only enable BUS_DMA_64BIT for PCIe.
> 
> kettenis@ preferes the check this way.
> 
> ok?

ok kettenis@

> Index: dev/pci/if_em.c
> ===================================================================
> RCS file: /data/mirror/openbsd/cvs/src/sys/dev/pci/if_em.c,v
> diff -u -p -r1.379 if_em.c
> --- dev/pci/if_em.c	14 Jul 2025 11:52:43 -0000	1.379
> +++ dev/pci/if_em.c	3 Mar 2026 19:46:42 -0000
> @@ -534,6 +534,10 @@ em_attach(struct device *parent, struct 
>  	sc->hw.min_frame_size = 
>  	    ETHER_MIN_LEN + ETHER_CRC_LEN;
>  
> +	em_get_bus_info(&sc->hw);
> +	if (sc->hw.bus_type == em_bus_type_pci_express)
> +		sc->sc_dmaflags |= BUS_DMA_64BIT;
> +
>  	if (em_allocate_desc_rings(sc) != 0) {
>  		printf("%s: Unable to allocate descriptor ring memory\n",
>  		    DEVNAME(sc));
> @@ -610,11 +614,10 @@ em_attach(struct device *parent, struct 
>  		    DEVNAME(sc));
>  
>  	/* Identify 82544 on PCI-X */
> -	em_get_bus_info(&sc->hw);
>  	if (sc->hw.bus_type == em_bus_type_pcix &&
>  	    sc->hw.mac_type == em_82544)
>  		sc->pcix_82544 = TRUE;
> -        else
> +	else
>  		sc->pcix_82544 = FALSE;
>  
>  	sc->hw.icp_xxxx_is_link_up = FALSE;
> @@ -2158,12 +2161,13 @@ em_dma_malloc(struct em_softc *sc, bus_s
>  	int r;
>  
>  	r = bus_dmamap_create(sc->sc_dmat, size, 1,
> -	    size, 0, BUS_DMA_WAITOK | BUS_DMA_ALLOCNOW, &dma->dma_map);
> +	    size, 0, BUS_DMA_WAITOK | BUS_DMA_ALLOCNOW | sc->sc_dmaflags,
> +	    &dma->dma_map);
>  	if (r != 0)
>  		return (r);
>  
>  	r = bus_dmamem_alloc(sc->sc_dmat, size, PAGE_SIZE, 0, &dma->dma_seg,
> -	    1, &dma->dma_nseg, BUS_DMA_WAITOK | BUS_DMA_ZERO);
> +	    1, &dma->dma_nseg, BUS_DMA_WAITOK | BUS_DMA_ZERO | sc->sc_dmaflags);
>  	if (r != 0)
>  		goto destroy;
>  
> @@ -2250,10 +2254,12 @@ em_setup_transmit_structures(struct em_s
>  			pkt = &que->tx.sc_tx_pkts_ring[i];
>  			error = bus_dmamap_create(sc->sc_dmat, EM_TSO_SIZE,
>  			    EM_MAX_SCATTER / (sc->pcix_82544 ? 2 : 1),
> -			    EM_TSO_SEG_SIZE, 0, BUS_DMA_NOWAIT, &pkt->pkt_map);
> +			    EM_TSO_SEG_SIZE, 0,
> +			    BUS_DMA_NOWAIT | sc->sc_dmaflags,
> +			    &pkt->pkt_map);
>  			if (error != 0) {
> -				printf("%s: Unable to create TX DMA map\n",
> -				    DEVNAME(sc));
> +				printf("%s: Unable to create TX DMA map, "
> +				    "error %d\n", DEVNAME(sc), error);
>  				goto fail;
>  			}
>  		}
> @@ -2772,11 +2778,11 @@ em_allocate_receive_structures(struct em
>  			pkt = &que->rx.sc_rx_pkts_ring[i];
>  
>  			error = bus_dmamap_create(sc->sc_dmat, EM_MCLBYTES, 1,
> -			    EM_MCLBYTES, 0, BUS_DMA_NOWAIT, &pkt->pkt_map);
> +			    EM_MCLBYTES, 0, BUS_DMA_NOWAIT | sc->sc_dmaflags,
> +			    &pkt->pkt_map);
>  			if (error != 0) {
> -				printf("%s: em_allocate_receive_structures: "
> -				    "bus_dmamap_create failed; error %u\n",
> -				    DEVNAME(sc), error);
> +				printf("%s: Unable to create RX DMA map, "
> +				    "error %d\n", DEVNAME(sc), error);
>  				goto fail;
>  			}
>  
> Index: dev/pci/if_em.h
> ===================================================================
> RCS file: /data/mirror/openbsd/cvs/src/sys/dev/pci/if_em.h,v
> diff -u -p -r1.83 if_em.h
> --- dev/pci/if_em.h	16 Feb 2024 22:30:54 -0000	1.83
> +++ dev/pci/if_em.h	3 Mar 2026 19:41:04 -0000
> @@ -385,6 +385,7 @@ struct em_softc {
>  	struct arpcom	sc_ac;
>  
>  	bus_dma_tag_t	sc_dmat;
> +	int		sc_dmaflags;
>  
>  	struct em_hw	hw;
>  
> 
>