On Sun, 07 Jun 2026 18:01:03 +0200,
Mark Kettenis <[email protected]> wrote:
>
> > Date: Sun, 07 Jun 2026 17:31:30 +0200
> > From: "Kirill A. Korinsky" <[email protected]>
> >
> > bugs@,
> >
> > when I tried to install OpenBSD/armv7 into qemu it hits panic.
>
> The panic isn't the problem. That just happens because of an
> alignment fault that happens:
>
Thanks for direction.
Seems that vio removes the virtio net header before handing packets to the
Ethernet input path. With the 12 byte modern virtio net header this leaves
the Ethernet frame at an address where the following IP header is not 32 bit
aligned; armv7 traps on the resulting unaligned access while processing DHCP
traffic.
Tested on my qemu setup, it boots.
Ok?
Index: sys/dev/pv/if_vio.c
===================================================================
RCS file: /home/cvs/src/sys/dev/pv/if_vio.c,v
diff -u -p -r1.79 if_vio.c
--- sys/dev/pv/if_vio.c 16 Apr 2026 21:00:00 -0000 1.79
+++ sys/dev/pv/if_vio.c 7 Jun 2026 22:28:23 -0000
@@ -297,6 +297,7 @@ struct vio_softc {
uint16_t sc_rxr_lwm;
int sc_tx_slots_per_req;
int sc_rx_mbuf_size;
+ int sc_rx_mbuf_offset;
enum vio_ctrl_state sc_ctrl_inuse;
@@ -747,6 +748,8 @@ negotiate:
} else {
sc->sc_hdr_size = offsetof(struct virtio_net_hdr, num_buffers);
}
+ sc->sc_rx_mbuf_offset = (ETHER_ALIGN + sizeof(uint32_t) -
+ sc->sc_hdr_size % sizeof(uint32_t)) % sizeof(uint32_t);
ifp->if_capabilities = 0;
ifp->if_flags = IFF_BROADCAST | IFF_SIMPLEX | IFF_MULTICAST;
@@ -780,9 +783,11 @@ negotiate:
if (!virtio_has_feature(vsc, VIRTIO_NET_F_MRG_RXBUF)) {
if (device_mtu)
sc->sc_rx_mbuf_size = MAX(sc->sc_rx_mbuf_size,
- device_mtu + sc->sc_hdr_size + ETHER_HDR_LEN);
+ sc->sc_rx_mbuf_offset + device_mtu +
+ sc->sc_hdr_size + ETHER_HDR_LEN);
ifp->if_hardmtu = MIN(ifp->if_hardmtu,
- sc->sc_rx_mbuf_size - sc->sc_hdr_size - ETHER_HDR_LEN);
+ sc->sc_rx_mbuf_size - sc->sc_rx_mbuf_offset -
+ sc->sc_hdr_size - ETHER_HDR_LEN);
}
txsize = ifp->if_hardmtu + sc->sc_hdr_size + ETHER_HDR_LEN;
@@ -790,13 +795,16 @@ negotiate:
virtio_has_feature(vsc, VIRTIO_NET_F_HOST_TSO6))
txsize = MAXMCLBYTES + sc->sc_hdr_size;
- rxsize = ifp->if_hardmtu + sc->sc_hdr_size + ETHER_HDR_LEN;
+ rxsize = ifp->if_hardmtu + sc->sc_rx_mbuf_offset +
+ sc->sc_hdr_size + ETHER_HDR_LEN;
if (virtio_has_feature(vsc, VIRTIO_NET_F_GUEST_TSO4) ||
virtio_has_feature(vsc, VIRTIO_NET_F_GUEST_TSO6))
- rxsize = MAXMCLBYTES + sc->sc_hdr_size;
+ rxsize = MAXMCLBYTES + sc->sc_rx_mbuf_offset +
+ sc->sc_hdr_size;
printf("\n");
- sc->sc_rxr_lwm = 2 * howmany(rxsize, sc->sc_rx_mbuf_size);
+ sc->sc_rxr_lwm = 2 * howmany(rxsize,
+ sc->sc_rx_mbuf_size - sc->sc_rx_mbuf_offset);
/* defrag for longer mbuf chains */
tx_max_segments = 16;
@@ -1438,7 +1446,7 @@ vio_add_rx_mbuf(struct vio_softc *sc, st
return ENOBUFS;
vioq->viq_rxmbufs[i] = m;
m->m_len = m->m_pkthdr.len = m->m_ext.ext_size;
- /* XXX m_adj ETHER_ALIGN ? */
+ m_adj(m, sc->sc_rx_mbuf_offset);
r = bus_dmamap_load_mbuf(sc->sc_virtio->sc_dmat,
vioq->viq_rxdmamaps[i], m, BUS_DMA_READ|BUS_DMA_NOWAIT);
if (r) {
@@ -1509,7 +1517,8 @@ vio_populate_rx_mbufs(struct vio_softc *
0, sc->sc_hdr_size, 0);
virtio_enqueue_p(vq, slot, vioq->viq_rxdmamaps[slot],
sc->sc_hdr_size,
- sc->sc_rx_mbuf_size - sc->sc_hdr_size, 0);
+ sc->sc_rx_mbuf_size - sc->sc_rx_mbuf_offset -
+ sc->sc_hdr_size, 0);
}
virtio_enqueue_commit(vsc, vq, slot, 0);
done = 1;
--
wbr, Kirill
