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commit 0b725a2ca61bedc33a2a63d0451d528b268cf975 net: Remove ndo_xmit_flush netdev operation, use signalling instead. added code that looks at skb->xmit_more after the skb has been put in TX VQ. Since some paths process the ring and free the skb immediately, this can cause use after free. Fix by storing xmit_more in a local variable. Cc: David S. Miller <davem at davemloft.net> Signed-off-by: Michael S. Tsirkin <mst at redhat.com> --- Da...

commit 0b725a2ca61bedc33a2a63d0451d528b268cf975 net: Remove ndo_xmit_flush netdev operation, use signalling instead. added code that looks at skb->xmit_more after the skb has been put in TX VQ. Since some paths process the ring and free the skb immediately, this can cause use after free. Fix by storing xmit_more in a local variable. Cc: David S. Miller <davem at davemloft.net> Signed-off-by: Michael S. Tsirkin <mst at redhat.com> --- Da...

With the help of xmit_more and virtqueue_enable_cb_avail(), this patch enable tx interrupt only for the final skb in the chain if needed. This will help to mitigate tx interrupts. Cc: Rusty Russell <rusty at rustcorp.com.au> Cc: Michael S. Tsirkin <mst at redhat.com> Signed-off-by: Jason Wang <jasowang at re...

With the help of xmit_more and virtqueue_enable_cb_avail(), this patch enable tx interrupt only for the final skb in the chain if needed. This will help to mitigate tx interrupts. Cc: Rusty Russell <rusty at rustcorp.com.au> Cc: Michael S. Tsirkin <mst at redhat.com> Signed-off-by: Jason Wang <jasowang at re...

On Wed, Oct 15, 2014 at 03:25:30PM +0800, Jason Wang wrote: > With the help of xmit_more and virtqueue_enable_cb_avail(), this patch > enable tx interrupt only for the final skb in the chain if > needed. This will help to mitigate tx interrupts. > > Cc: Rusty Russell <rusty at rustcorp.com.au> > Cc: Michael S. Tsirkin <mst at redhat.com> > Signed-off-by:...

On 10/15/2014 06:22 PM, Michael S. Tsirkin wrote: > On Wed, Oct 15, 2014 at 03:25:30PM +0800, Jason Wang wrote: >> With the help of xmit_more and virtqueue_enable_cb_avail(), this patch >> enable tx interrupt only for the final skb in the chain if >> needed. This will help to mitigate tx interrupts. >> >> Cc: Rusty Russell <rusty at rustcorp.com.au> >> Cc: Michael S. Tsirkin <mst at redhat.com>...

From: Michael S. Tsirkin > commit 0b725a2ca61bedc33a2a63d0451d528b268cf975 > net: Remove ndo_xmit_flush netdev operation, use signalling instead. > > added code that looks at skb->xmit_more after the skb has > been put in TX VQ. Since some paths process the ring and free the skb > immediately, this can cause use after free. > > Fix by storing xmit_more in a local variable. > > Cc: David S. Miller <davem at davemloft.net> > Signed-off-by: Michael S. Tsirki...

On Wed, 2014-10-15 at 16:23 +0300, Michael S. Tsirkin wrote: > commit 0b725a2ca61bedc33a2a63d0451d528b268cf975 > net: Remove ndo_xmit_flush netdev operation, use signalling instead. > > added code that looks at skb->xmit_more after the skb has > been put in TX VQ. Since some paths process the ring and free the skb > immediately, this can cause use after free. > > Fix by storing xmit_more in a local variable. > > Cc: David S. Miller <davem at davemloft.net> > Signed-off-by: Michael S. Tsirki...

On 10/31/2014 11:36 AM, Eric Dumazet wrote: > On Wed, 2014-10-15 at 16:23 +0300, Michael S. Tsirkin wrote: >> commit 0b725a2ca61bedc33a2a63d0451d528b268cf975 >> net: Remove ndo_xmit_flush netdev operation, use signalling instead. >> >> added code that looks at skb->xmit_more after the skb has >> been put in TX VQ. Since some paths process the ring and free the skb >> immediately, this can cause use after free. >> >> Fix by storing xmit_more in a local variable. >> >> Cc: David S. Miller <davem at davemloft.net> >> Signed...

On 10/15/2014 06:22 PM, Michael S. Tsirkin wrote: > On Wed, Oct 15, 2014 at 03:25:30PM +0800, Jason Wang wrote: >> With the help of xmit_more and virtqueue_enable_cb_avail(), this patch >> enable tx interrupt only for the final skb in the chain if >> needed. This will help to mitigate tx interrupts. >> >> Cc: Rusty Russell <rusty at rustcorp.com.au> >> Cc: Michael S. Tsirkin <mst at redhat.com>...

On 10/31/2014 11:36 AM, Eric Dumazet wrote: > On Wed, 2014-10-15 at 16:23 +0300, Michael S. Tsirkin wrote: >> commit 0b725a2ca61bedc33a2a63d0451d528b268cf975 >> net: Remove ndo_xmit_flush netdev operation, use signalling instead. >> >> added code that looks at skb->xmit_more after the skb has >> been put in TX VQ. Since some paths process the ring and free the skb >> immediately, this can cause use after free. >> >> Fix by storing xmit_more in a local variable. >> >> Cc: David S. Miller <davem at davemloft.net> >> Signed...

...complete(napi, sq->vq, 0); > @@ -1505,13 +1509,15 @@ static netdev_tx_t start_xmit(struct sk_buff *skb, struct net_device *dev) > struct send_queue *sq = &vi->sq[qnum]; > int err; > struct netdev_queue *txq = netdev_get_tx_queue(dev, qnum); > - bool kick = !skb->xmit_more; > + bool more = skb->xmit_more; > bool use_napi = sq->napi.weight; > + unsigned int bytes = skb->len; > + bool kick; > > /* Free up any pending old buffers before queueing new ones. */ > - free_old_xmit_skbs(sq); > + free_old_xmit_skbs(sq, txq, use_napi);...

...complete(napi, sq->vq, 0); > @@ -1505,13 +1509,15 @@ static netdev_tx_t start_xmit(struct sk_buff *skb, struct net_device *dev) > struct send_queue *sq = &vi->sq[qnum]; > int err; > struct netdev_queue *txq = netdev_get_tx_queue(dev, qnum); > - bool kick = !skb->xmit_more; > + bool more = skb->xmit_more; > bool use_napi = sq->napi.weight; > + unsigned int bytes = skb->len; > + bool kick; > > /* Free up any pending old buffers before queueing new ones. */ > - free_old_xmit_skbs(sq); > + free_old_xmit_skbs(sq, txq, use_napi);...

...; struct virtnet_info *vi = netdev_priv(dev); > int qnum = skb_get_queue_mapping(skb); > struct send_queue *sq = &vi->sq[qnum]; > + struct net_device *vf_netdev; > int err; > struct netdev_queue *txq = netdev_get_tx_queue(dev, qnum); > bool kick = !skb->xmit_more; > bool use_napi = sq->napi.weight; > > + /* If VF is present and up then redirect packets > + * called with rcu_read_lock_bh > + */ > + vf_netdev = rcu_dereference_bh(vi->vf_netdev); > + if (vf_netdev && netif_running(vf_netdev) && > + !ne...

...; struct virtnet_info *vi = netdev_priv(dev); > int qnum = skb_get_queue_mapping(skb); > struct send_queue *sq = &vi->sq[qnum]; > + struct net_device *vf_netdev; > int err; > struct netdev_queue *txq = netdev_get_tx_queue(dev, qnum); > bool kick = !skb->xmit_more; > bool use_napi = sq->napi.weight; > > + /* If VF is present and up then redirect packets > + * called with rcu_read_lock_bh > + */ > + vf_netdev = rcu_dereference_bh(vi->vf_netdev); > + if (vf_netdev && netif_running(vf_netdev) && > + !ne...

...k to make sure used event never go back. This will let the napi not enable the callbacks wrongly after delayed callbacks was used. - For bulk dequeuing, there's no need to enable tx interrupt for each packet. The last patch only enable tx interrupt for the final skb in the chain through xmit_more and a new helper to publish current avail idx as used event. This series fixes several issues of original rfc pointed out by Michael. Smoking test is done, and will do complete netperf test. Send the seires for early review. Thanks Jason Wang (6): virtio: make sure used event never go back...

...k to make sure used event never go back. This will let the napi not enable the callbacks wrongly after delayed callbacks was used. - For bulk dequeuing, there's no need to enable tx interrupt for each packet. The last patch only enable tx interrupt for the final skb in the chain through xmit_more and a new helper to publish current avail idx as used event. This series fixes several issues of original rfc pointed out by Michael. Smoking test is done, and will do complete netperf test. Send the seires for early review. Thanks Jason Wang (6): virtio: make sure used event never go back...

...@@ -1505,13 +1509,15 @@ static netdev_tx_t start_xmit(struct sk_buff *skb, struct net_device *dev) >>> struct send_queue *sq = &vi->sq[qnum]; >>> int err; >>> struct netdev_queue *txq = netdev_get_tx_queue(dev, qnum); >>> - bool kick = !skb->xmit_more; >>> + bool more = skb->xmit_more; >>> bool use_napi = sq->napi.weight; >>> + unsigned int bytes = skb->len; >>> + bool kick; >>> /* Free up any pending old buffers before queueing new ones. */ >>> - free_old_xmit_skbs(sq); &gt...

...@@ -1505,13 +1509,15 @@ static netdev_tx_t start_xmit(struct sk_buff *skb, struct net_device *dev) >>> struct send_queue *sq = &vi->sq[qnum]; >>> int err; >>> struct netdev_queue *txq = netdev_get_tx_queue(dev, qnum); >>> - bool kick = !skb->xmit_more; >>> + bool more = skb->xmit_more; >>> bool use_napi = sq->napi.weight; >>> + unsigned int bytes = skb->len; >>> + bool kick; >>> /* Free up any pending old buffers before queueing new ones. */ >>> - free_old_xmit_skbs(sq); &gt...

Now that we have brought the virtio overhead way down with a fast packed ring implementation, we seem to be actually observing TCP drops indicative of bufferbloat. So let's try to enable TSQ. Note: it isn't clear that the default pacing is great for the virt usecase. It's worth trying to play with sk_pacing_shift_update to see what happens. For this reason, and for a more important