diff options
| author | Stefan Fritsch <sf@cvs.openbsd.org> | 2017-05-27 10:22:07 +0000 |
|---|---|---|
| committer | Stefan Fritsch <sf@cvs.openbsd.org> | 2017-05-27 10:22:07 +0000 |
| commit | efe876738870d01e8e2fe1edbbb1c8d074718cea (patch) | |
| tree | 803ed2d0c18948802d3c271a97b9f1e3c8c6ef7e | |
| parent | 89d2651ee6f9c3fe7f1d5f591c1a16ccc8466726 (diff) | |
virtio: Remove MINSEG_INDIRECT
Remove MINSEG_INDIRECT as a tweakable define. Always use indirect
descriptors if we have more than 1 segment. Add a comment to document
the way if_vio.c uses maxnsegs in virtio_alloc_vq() to disable
indirect descriptors for a queue.
Based on a diff from krw@
| -rw-r--r-- | sys/dev/pv/virtio.c | 27 |
1 files changed, 11 insertions, 16 deletions
diff --git a/sys/dev/pv/virtio.c b/sys/dev/pv/virtio.c index 14b28c76bf6..ac7732266d1 100644 --- a/sys/dev/pv/virtio.c +++ b/sys/dev/pv/virtio.c @@ -1,4 +1,4 @@ -/* $OpenBSD: virtio.c,v 1.3 2017/05/26 15:30:21 sf Exp $ */ +/* $OpenBSD: virtio.c,v 1.4 2017/05/27 10:22:06 sf Exp $ */ /* $NetBSD: virtio.c,v 1.3 2011/11/02 23:05:52 njoly Exp $ */ /* @@ -38,8 +38,6 @@ #include <dev/pv/virtioreg.h> #include <dev/pv/virtiovar.h> -#define MINSEG_INDIRECT 2 /* use indirect if nsegs >= this value */ - #if VIRTIO_DEBUG #define VIRTIO_ASSERT(x) KASSERT(x) #else @@ -275,6 +273,10 @@ virtio_init_vq(struct virtio_softc *sc, struct virtqueue *vq, int reinit) /* * Allocate/free a vq. + * + * maxnsegs denotes how much space should be allocated for indirect + * descriptors. maxnsegs == 1 can be used to disable use indirect + * descriptors for this queue. */ int virtio_alloc_vq(struct virtio_softc *sc, struct virtqueue *vq, int index, @@ -304,10 +306,7 @@ virtio_alloc_vq(struct virtio_softc *sc, struct virtqueue *vq, int index, allocsize2 = VIRTQUEUE_ALIGN(sizeof(uint16_t) * hdrlen + sizeof(struct vring_used_elem) * vq_size); /* allocsize3: indirect table */ - /* XXX: This is rather inefficient. In practice only a fraction of this - * XXX: memory will be used. - */ - if (sc->sc_indirect && maxnsegs >= MINSEG_INDIRECT) + if (sc->sc_indirect && maxnsegs > 1) allocsize3 = sizeof(struct vring_desc) * maxnsegs * vq_size; else allocsize3 = 0; @@ -511,23 +510,17 @@ virtio_enqueue_prep(struct virtqueue *vq, int *slotp) int virtio_enqueue_reserve(struct virtqueue *vq, int slot, int nsegs) { - int indirect; struct vq_entry *qe1 = &vq->vq_entries[slot]; VIRTIO_ASSERT(qe1->qe_next == -1); VIRTIO_ASSERT(1 <= nsegs && nsegs <= vq->vq_num); - if ((vq->vq_indirect != NULL) && (nsegs >= MINSEG_INDIRECT) && - (nsegs <= vq->vq_maxnsegs)) - indirect = 1; - else - indirect = 0; - qe1->qe_indirect = indirect; - - if (indirect) { + if (vq->vq_indirect != NULL && nsegs > 1 && nsegs <= vq->vq_maxnsegs) { struct vring_desc *vd; int i; + qe1->qe_indirect = 1; + vd = &vq->vq_desc[qe1->qe_index]; vd->addr = vq->vq_dmamap->dm_segs[0].ds_addr + vq->vq_indirectoffset; @@ -551,6 +544,8 @@ virtio_enqueue_reserve(struct virtqueue *vq, int slot, int nsegs) struct vq_entry *qe; int i, s; + qe1->qe_indirect = 0; + vd = &vq->vq_desc[0]; qe1->qe_desc_base = vd; qe1->qe_next = qe1->qe_index; |