netmap: vtnet: stop krings during interface reset

Similarly to what done for iflib in 1d238b07d5d4d9660ae0e,
this patch prevents access to the krings during the interface
reset triggered by netmap_register().

MFC after:	1 week

(cherry picked from commit 9ac59d42c0b4b6cd9c36a5dace7f49753c2e175a)

netmap: vtnet: enable/disable krings on any interface reinit

See 3d65fd97e85ab807f3b for a detailed explanation.

PR:             252453
MFC after:      1 week

(cherry picked from commit bb714db6d39583a9fbf5d11849c5e2365e7c0d80)

netmap: vtnet: fix RX initialization after netmap_reset()

At device reset, we must not publish those netmap receive buffers
that are owned by userspace (nm_kr_rxspace).

MFC after:	1 week

(cherry picked from commit 3005e10ddbfbec3ecf46a080607bb0d85986eee5)

3 files changed, 27 insertions, 8 deletions

diff --git a/sys/dev/netmap/if_vtnet_netmap.h b/sys/dev/netmap/if_vtnet_netmap.h
index 0f686ed60788..cd652938bca5 100644
--- a/sys/dev/netmap/if_vtnet_netmap.h
+++ b/sys/dev/netmap/if_vtnet_netmap.h
@@ -50,7 +50,7 @@ vtnet_netmap_reg(struct netmap_adapter *na, int state)
 	    : VTNET_INIT_NETMAP_EXIT);
 	VTNET_CORE_UNLOCK(sc);
 
-	return 0;
+	return (0);
 }
 
 
@@ -213,20 +213,25 @@ vtnet_netmap_rxq_populate(struct vtnet_rxq *rxq)
 	struct netmap_kring *kring;
 	struct netmap_slot *slot;
 	int error;
+	int num;
 
 	slot = netmap_reset(na, NR_RX, rxq->vtnrx_id, 0);
 	if (slot == NULL)
 		return -1;
 	kring = na->rx_rings[rxq->vtnrx_id];
 
-	/* Expose all the RX netmap buffers we can. In case of no indirect
+	/*
+	 * 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. 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);
+	 * accommodate. We need to start from kring->nr_hwtail, which is 0
+	 * on the first netmap register and may be different from 0 if a
+	 * virtio re-init (caused by a netma register or i.e., ifconfig)
+	 * happens while the device is in use by netmap.
+	 */
+	rxq->vtnrx_nm_refill = kring->nr_hwtail;
+	num = na->num_rx_desc - 1 - nm_kr_rxspace(kring);
+	error = vtnet_netmap_kring_refill(kring, num);
 	virtqueue_notify(rxq->vtnrx_vq);
 
 	return error;
@@ -256,7 +261,7 @@ vtnet_netmap_rxsync(struct netmap_kring *kring, int flags)
 	 * First part: import newly received packets.
 	 * Only accept our own buffers (matching the token). We should only get
 	 * matching buffers. The hwtail should never overrun hwcur, because
-	 * we publish only N-1 receive buffers (and non N).
+	 * we publish only N-1 receive buffers (and not N).
 	 * In any case we must not leave this routine with the interrupts
 	 * disabled, pending packets in the VQ and hwtail == (hwcur - 1),
 	 * otherwise the pending packets could stall.
diff --git a/sys/dev/netmap/netmap.c b/sys/dev/netmap/netmap.c
index 075c27b7a597..f75567565bf1 100644
--- a/sys/dev/netmap/netmap.c
+++ b/sys/dev/netmap/netmap.c
@@ -616,6 +616,10 @@ netmap_set_all_rings(struct netmap_adapter *na, int stopped)
 	if (!nm_netmap_on(na))
 		return;
 
+	if (netmap_verbose) {
+		nm_prinf("%s: %sable all rings", na->name,
+		    (stopped ? "dis" : "en"));
+	}
 	for_rx_tx(t) {
 		for (i = 0; i < netmap_real_rings(na, t); i++) {
 			netmap_set_ring(na, i, t, stopped);
diff --git a/sys/dev/virtio/network/if_vtnet.c b/sys/dev/virtio/network/if_vtnet.c
index ff0a07672f49..6018fe56e360 100644
--- a/sys/dev/virtio/network/if_vtnet.c
+++ b/sys/dev/virtio/network/if_vtnet.c
@@ -2833,6 +2833,11 @@ vtnet_stop(struct vtnet_softc *sc)
 	/* Only advisory. */
 	vtnet_disable_interrupts(sc);
 
+#ifdef DEV_NETMAP
+	/* Stop any pending txsync/rxsync and disable them. */
+	netmap_disable_all_rings(ifp);
+#endif /* DEV_NETMAP */
+
 	/*
 	 * Stop the host adapter. This resets it to the pre-initialized
 	 * state. It will not generate any interrupts until after it is
@@ -3098,6 +3103,11 @@ vtnet_init_locked(struct vtnet_softc *sc, int init_mode)
 	vtnet_update_link_status(sc);
 	callout_reset(&sc->vtnet_tick_ch, hz, vtnet_tick, sc);
 
+#ifdef DEV_NETMAP
+	/* Re-enable txsync/rxsync. */
+	netmap_enable_all_rings(ifp);
+#endif /* DEV_NETMAP */
+
 	return;
 
 fail: