Hi,

igc(4) also works for me with 64 bit DMA.  Tested with

igc1 at pci16 dev 0 function 0 "Intel I225-LM" rev 0x03, msix, 4 queues, address 24:5e:be:8f:0f:1d

ok?

bluhm

Index: dev/pci/if_igc.c
===================================================================
RCS file: /data/mirror/openbsd/cvs/src/sys/dev/pci/if_igc.c,v
diff -u -p -r1.30 if_igc.c
--- dev/pci/if_igc.c	17 Dec 2025 01:14:42 -0000	1.30
+++ dev/pci/if_igc.c	24 Feb 2026 21:54:13 -0000
@@ -737,11 +737,11 @@ igc_dma_malloc(struct igc_softc *sc, bus
 
 	dma->dma_tag = os->os_pa.pa_dmat;
 
-	if (bus_dmamap_create(dma->dma_tag, size, 1, size, 0, BUS_DMA_NOWAIT,
-	    &dma->dma_map))
+	if (bus_dmamap_create(dma->dma_tag, size, 1, size, 0,
+	    BUS_DMA_NOWAIT | BUS_DMA_64BIT, &dma->dma_map))
 		return 1;
 	if (bus_dmamem_alloc(dma->dma_tag, size, PAGE_SIZE, 0, &dma->dma_seg,
-	    1, &dma->dma_nseg, BUS_DMA_NOWAIT))
+	    1, &dma->dma_nseg, BUS_DMA_NOWAIT | BUS_DMA_64BIT))
 		goto destroy;
 	if (bus_dmamem_map(dma->dma_tag, &dma->dma_seg, dma->dma_nseg, size,
 	    &dma->dma_vaddr, BUS_DMA_NOWAIT | BUS_DMA_COHERENT))
@@ -1855,10 +1855,11 @@ igc_allocate_transmit_buffers(struct igc
 	for (i = 0; i < sc->num_tx_desc; i++) {
 		txbuf = &txr->tx_buffers[i];
 		error = bus_dmamap_create(txr->txdma.dma_tag, IGC_TSO_SIZE,
-		    IGC_MAX_SCATTER, PAGE_SIZE, 0, BUS_DMA_NOWAIT, &txbuf->map);
+		    IGC_MAX_SCATTER, PAGE_SIZE, 0,
+		    BUS_DMA_NOWAIT | BUS_DMA_64BIT, &txbuf->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;
 		}
 	}
@@ -2161,10 +2162,10 @@ igc_allocate_receive_buffers(struct igc_
 	for (i = 0; i < sc->num_rx_desc; i++, rxbuf++) {
 		error = bus_dmamap_create(rxr->rxdma.dma_tag,
 		    sc->rx_mbuf_sz, 1, sc->rx_mbuf_sz, 0,
-		    BUS_DMA_NOWAIT, &rxbuf->map);
+		    BUS_DMA_NOWAIT | BUS_DMA_64BIT, &rxbuf->map);
 		if (error) {
-			printf("%s: Unable to create RX DMA map\n",
-			    DEVNAME(sc));
+			printf("%s: Unable to create RX DMA map, error %d\n",
+			    DEVNAME(sc), error);
 			goto fail;
 		}
 	}