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em 64 bit dma
On Fri, Feb 27, 2026 at 12:58:15PM -0500, Brad Smith wrote:
> On 2026-02-27 12:36 p.m., Alexander Bluhm wrote:
> > Hi,
> >
> > I have tested 64 bit dma for em(4) with
> >
> > em0 at pci0 dev 25 function 0 "Intel 82579LM" rev 0x04: msi, address 3c:97:0e:a7:09:b2
> > em0 at pci2 dev 0 function 0 "Intel 82571EB" rev 0x06: apic 2 int 8, address 00:1b:21:7b:d1:10
> > em2 at pci3 dev 0 function 0 "Intel 82580" rev 0x01: msi, address 90:e2:ba:78:7c:f0
> > em6 at pci4 dev 0 function 0 "Intel 82576" rev 0x01: msi, address 00:1b:21:da:f6:ec
> > em8 at pci5 dev 0 function 0 "Intel I350" rev 0x01: msi, address 00:25:90:e7:ec:7c
> > em14 at pci11 dev 0 function 0 "Intel 82576" rev 0x01: msi, address 00:1b:21:60:58:28
> >
> > I only enable BUS_DMA_64BIT for PCIe.
> >
> > ok?
> >
> > bluhm
> >
> > 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 27 Feb 2026 17:30:06 -0000
> > @@ -534,6 +534,23 @@ em_attach(struct device *parent, struct
> > sc->hw.min_frame_size =
> > ETHER_MIN_LEN + ETHER_CRC_LEN;
> >
> > + em_get_bus_info(&sc->hw);
> > + switch (sc->hw.bus_type) {
> > + case em_bus_type_pcix:
> > + /* Identify 82544 on PCI-X */
> > + if (sc->hw.mac_type == em_82544)
> > + sc->pcix_82544 = TRUE;
> > + else
> > + sc->pcix_82544 = FALSE;
> > + break;
> > + case em_bus_type_pci_express:
> > + /* Only PCI-X and PCIe support 64 bit DMA */
>
> The comment doesn't match what the code does.
Sorry, that was a last minute change. Before there was a FALLTHROUGH
instead of break above. It seems that we want to be on the safe
side and disable 64 bit DMA for PCI-X.
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 27 Feb 2026 18:38:37 -0000
@@ -534,6 +534,23 @@ em_attach(struct device *parent, struct
sc->hw.min_frame_size =
ETHER_MIN_LEN + ETHER_CRC_LEN;
+ em_get_bus_info(&sc->hw);
+ switch (sc->hw.bus_type) {
+ case em_bus_type_pcix:
+ /* Identify 82544 on PCI-X */
+ if (sc->hw.mac_type == em_82544)
+ sc->pcix_82544 = TRUE;
+ else
+ sc->pcix_82544 = FALSE;
+ break;
+ case em_bus_type_pci_express:
+ /* Only PCIe support 64 bit DMA */
+ sc->sc_dmaflags |= BUS_DMA_64BIT;
+ break;
+ default:
+ break;
+ }
+
if (em_allocate_desc_rings(sc) != 0) {
printf("%s: Unable to allocate descriptor ring memory\n",
DEVNAME(sc));
@@ -609,14 +626,6 @@ em_attach(struct device *parent, struct
printf("%s: PHY reset is blocked due to SOL/IDER session.\n",
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
- sc->pcix_82544 = FALSE;
-
sc->hw.icp_xxxx_is_link_up = FALSE;
INIT_DEBUGOUT("em_attach: end");
@@ -2158,12 +2167,13 @@ 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 +2260,12 @@ 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 +2784,11 @@ 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 27 Feb 2026 17:01:30 -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;
em 64 bit dma