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netmap: vtnet: add vtnrx_nm_refill index to receive queues

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The new index tracks the next netmap slot that is going
to be enqueued into the virtqueue. The index is necessary
to prevent the receive VQ and the netmap rx ring from going
out of sync, considering that we never enqueue N slots, but
at most N-1. This change fixes a bug that causes the VQ
and the netmap ring to go out of sync after N-1 packets
have been received.

MFC after:	1 week
This commit is contained in:
Vincenzo Maffione 2020-06-03 17:42:17 +00:00
parent 78a3645fd2
commit 2d769e25b1
2 changed files with 31 additions and 20 deletions
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50
sys/dev/netmap/if_vtnet_netmap.h
View File

@ -196,9 +196,11 @@ vtnet_netmap_txsync(struct netmap_kring *kring, int flags)
}
/*
* Publish (up to) num netmap receive buffers to the host,
* starting from the first one that the user made available
* (kring->nr_hwcur).
* Publish 'num 'netmap receive buffers to the host, starting
* from the next available one (rx->vtnrx_nm_refill).
* Return a positive error code on error, and 0 on success.
* If we could not publish all of the buffers that's an error,
* since the netmap ring and the virtqueue would go out of sync.
*/
static int
vtnet_netmap_kring_refill(struct netmap_kring *kring, u_int num)
@ -208,7 +210,7 @@ vtnet_netmap_kring_refill(struct netmap_kring *kring, u_int num)
struct netmap_ring *ring = kring->ring;
u_int ring_nr = kring->ring_id;
u_int const lim = kring->nkr_num_slots - 1;
u_int nm_i = kring->nr_hwcur;
u_int nm_i;
/* device-specific */
struct vtnet_softc *sc = ifp->if_softc;
@ -219,7 +221,8 @@ vtnet_netmap_kring_refill(struct netmap_kring *kring, u_int num)
struct sglist_seg ss[2];
struct sglist sg = { ss, 0, 0, 2 };
for (; num > 0; nm_i = nm_next(nm_i, lim), num--) {
for (nm_i = rxq->vtnrx_nm_refill; num > 0;
nm_i = nm_next(nm_i, lim), num--) {
struct netmap_slot *slot = &ring->slot[nm_i];
uint64_t paddr;
void *addr = PNMB(na, slot, &paddr);
@ -227,7 +230,7 @@ vtnet_netmap_kring_refill(struct netmap_kring *kring, u_int num)
if (addr == NETMAP_BUF_BASE(na)) { /* bad buf */
if (netmap_ring_reinit(kring))
return -1;
return EFAULT;
}
slot->flags &= ~NS_BUF_CHANGED;
@ -240,14 +243,14 @@ vtnet_netmap_kring_refill(struct netmap_kring *kring, u_int num)
err = virtqueue_enqueue(vq, /*cookie=*/rxq, &sg,
/*readable=*/0, /*writeable=*/sg.sg_nseg);
if (unlikely(err)) {
if (err != ENOSPC)
nm_prerr("virtqueue_enqueue(%s) failed: %d",
kring->name, err);
nm_prerr("virtqueue_enqueue(%s) failed: %d",
kring->name, err);
break;
}
}
rxq->vtnrx_nm_refill = nm_i;
return nm_i;
return num == 0 ? 0 : ENOSPC;
}
/*
@ -274,11 +277,14 @@ vtnet_netmap_rxq_populate(struct vtnet_rxq *rxq)
/* Expose all the RX netmap buffers we can. In case of no indirect
* buffers, the number of netmap slots in the RX ring matches the
* maximum number of 2-elements sglist that the RX virtqueue can
* accommodate (minus 1 to avoid netmap ring wraparound). */
* accommodate. We need to start from kring->nr_hwcur, which is 0
* on netmap register and may be different from 0 if a virtio
* re-init happens while the device is in use by netmap. */
rxq->vtnrx_nm_refill = kring->nr_hwcur;
error = vtnet_netmap_kring_refill(kring, na->num_rx_desc - 1);
virtqueue_notify(rxq->vtnrx_vq);
return error < 0 ? ENXIO : 0;
return error;
}
/* Reconcile kernel and user view of the receive ring. */
@ -350,15 +356,19 @@ vtnet_netmap_rxsync(struct netmap_kring *kring, int flags)
*/
nm_i = kring->nr_hwcur; /* netmap ring index */
if (nm_i != head) {
int howmany = head - nm_i;
int nm_j;
int released;
int error;
if (howmany < 0)
howmany += kring->nkr_num_slots;
nm_j = vtnet_netmap_kring_refill(kring, howmany);
if (nm_j < 0)
return nm_j;
kring->nr_hwcur = nm_j;
released = head - nm_i;
if (released < 0)
released += kring->nkr_num_slots;
error = vtnet_netmap_kring_refill(kring, released);
if (error) {
nm_prerr("Failed to replenish RX VQ with %u sgs",
released);
return error;
}
kring->nr_hwcur = head;
virtqueue_notify(vq);
}

1
sys/dev/virtio/network/if_vtnetvar.h
View File

@ -80,6 +80,7 @@ struct vtnet_rxq {
struct taskqueue *vtnrx_tq;
struct task vtnrx_intrtask;
#ifdef DEV_NETMAP
uint32_t vtnrx_nm_refill;
struct virtio_net_hdr_mrg_rxbuf vtnrx_shrhdr;
#endif /* DEV_NETMAP */
char vtnrx_name[16];