Re: kern/52211: vioif stops on dmamap load error

["J. Hannken-Illjes" <hannken%eis.cs.tu-bs.de@localhost>]

The following reply was made to PR kern/52211; it has been noted by GNATS.

From: "J. Hannken-Illjes" <hannken%eis.cs.tu-bs.de@localhost>
To: gnats-bugs%NetBSD.org@localhost
Cc: 
Subject: Re: kern/52211: vioif stops on dmamap load error
Date: Thu, 11 May 2017 12:02:15 +0200

 > On 11. May 2017, at 11:26, Masanobu SAITOH <msaitoh%execsw.org@localhost> wrote:
 > 
 > New one:
 > 
 > Index: if_vioif.c
 > ===================================================================
 > RCS file: /cvsroot/src/sys/dev/pci/if_vioif.c,v
 > retrieving revision 1.34
 > diff -u -p -r1.34 if_vioif.c
 > --- if_vioif.c	28 Mar 2017 04:10:33 -0000	1.34
 > +++ if_vioif.c	11 May 2017 09:20:00 -0000
 > @@ -812,6 +812,7 @@ vioif_start(struct ifnet *ifp)
 >  	for (;;) {
 > 		int slot, r;
 > +		struct mbuf *newm;
 >  		IFQ_DEQUEUE(&ifp->if_snd, m);
 > @@ -833,7 +834,23 @@ retry:
 > 		r = bus_dmamap_load_mbuf(virtio_dmat(vsc),
 > 					 sc->sc_tx_dmamaps[slot],
 > 					 m, BUS_DMA_WRITE|BUS_DMA_NOWAIT);
 > -		if (r != 0) {
 > +		switch (r) {
 > +		case 0:
 > +			break;
 > +		case EFBIG:
 > +			printf("%s: loadup_mbuf() returned EFBIG (%d segs)\n",
 > +			    device_xname(sc->sc_dev),
 > +			    sc->sc_tx_dmamaps[slot]->dm_nsegs);
 > +			newm = m_defrag(m, M_NOWAIT);
 > +			if ((newm != NULL) &&
 > +			    (bus_dmamap_load_mbuf(virtio_dmat(vsc),
 > +				sc->sc_tx_dmamaps[slot],
 > +				newm, BUS_DMA_WRITE|BUS_DMA_NOWAIT) == 0)) {
 > +				m = newm;
 > +				break;
 > +			}
 > +			/* FALLTHROUGH */
 > +		default:
 > 			virtio_enqueue_abort(vsc, vq, slot);
 > 			aprint_error_dev(sc->sc_dev,
 > 			    "tx dmamap load failed, error code %d\n", r);
 
 The machine is running this patch now -- it may take weeks to trigger.
 
 We don't break the outer loop on error as the "break" after default
 now breaks the case and not the for loop but I hope it doesn't harm.
 
 > BTW, what hypervisor are you using?
 
 KVM from CentOS 6.8.
 
 --
 J. Hannken-Illjes - hannken%eis.cs.tu-bs.de@localhost - TU Braunschweig (Germany)