| Message ID | 20170113025206.4535.28363.stgit@john-Precision-Tower-5810 |
|---|---|
| State | Changes Requested, archived |
| Delegated to: | David Miller |
| Headers | show |
On 2017年01月13日 10:52, John Fastabend wrote: > Add support for XDP adjust head by allocating a 256B header region > that XDP programs can grow into. This is only enabled when a XDP > program is loaded. > > In order to ensure that we do not have to unwind queue headroom push > queue setup below bpf_prog_add. It reads better to do a prog ref > unwind vs another queue setup call. > > At the moment this code must do a full reset to ensure old buffers > without headroom on program add or with headroom on program removal > are not used incorrectly in the datapath. Ideally we would only > have to disable/enable the RX queues being updated but there is no > API to do this at the moment in virtio so use the big hammer. In > practice it is likely not that big of a problem as this will only > happen when XDP is enabled/disabled changing programs does not > require the reset. There is some risk that the driver may either > have an allocation failure or for some reason fail to correctly > negotiate with the underlying backend in this case the driver will > be left uninitialized. I have not seen this ever happen on my test > systems and for what its worth this same failure case can occur > from probe and other contexts in virtio framework. > > Signed-off-by: John Fastabend <john.r.fastabend@intel.com> > --- > drivers/net/virtio_net.c | 155 ++++++++++++++++++++++++++++++++++++++++------ > drivers/virtio/virtio.c | 9 ++- > include/linux/virtio.h | 3 + > 3 files changed, 144 insertions(+), 23 deletions(-) > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c > index 6041828..8b897e7 100644 > --- a/drivers/net/virtio_net.c > +++ b/drivers/net/virtio_net.c > @@ -28,6 +28,7 @@ > #include <linux/slab.h> > #include <linux/cpu.h> > #include <linux/average.h> > +#include <linux/pci.h> > #include <net/busy_poll.h> > > static int napi_weight = NAPI_POLL_WEIGHT; > @@ -159,6 +160,9 @@ struct virtnet_info { > /* Ethtool settings */ > u8 duplex; > u32 speed; > + > + /* Headroom allocated in RX Queue */ > + unsigned int headroom; If this could not be changed in anyway, better use a macro instead of a filed here. And there's even no need to add an extra parameter to add_recvbuf_mergeable(). > }; > > struct padded_vnet_hdr { > @@ -359,6 +363,7 @@ static void virtnet_xdp_xmit(struct virtnet_info *vi, > } > > if (vi->mergeable_rx_bufs) { > + xdp->data -= sizeof(struct virtio_net_hdr_mrg_rxbuf); Fail to understand why this is needed. We should have excluded vnet header from xdp->data even before bpf_prog_run_xdp(). > /* Zero header and leave csum up to XDP layers */ > hdr = xdp->data; > memset(hdr, 0, vi->hdr_len); > @@ -375,7 +380,9 @@ static void virtnet_xdp_xmit(struct virtnet_info *vi, > num_sg = 2; > sg_init_table(sq->sg, 2); > sg_set_buf(sq->sg, hdr, vi->hdr_len); > - skb_to_sgvec(skb, sq->sg + 1, 0, skb->len); > + skb_to_sgvec(skb, sq->sg + 1, > + xdp->data - xdp->data_hard_start, > + xdp->data_end - xdp->data); > } > err = virtqueue_add_outbuf(sq->vq, sq->sg, num_sg, > data, GFP_ATOMIC); > @@ -401,7 +408,6 @@ static struct sk_buff *receive_small(struct net_device *dev, > struct bpf_prog *xdp_prog; > > len -= vi->hdr_len; > - skb_trim(skb, len); > > rcu_read_lock(); > xdp_prog = rcu_dereference(rq->xdp_prog); > @@ -413,11 +419,15 @@ static struct sk_buff *receive_small(struct net_device *dev, > if (unlikely(hdr->hdr.gso_type || hdr->hdr.flags)) > goto err_xdp; > > - xdp.data = skb->data; > + xdp.data_hard_start = skb->data; > + xdp.data = skb->data + vi->headroom; > xdp.data_end = xdp.data + len; > act = bpf_prog_run_xdp(xdp_prog, &xdp); > switch (act) { > case XDP_PASS: > + /* Recalculate length in case bpf program changed it */ > + len = xdp.data_end - xdp.data; > + __skb_pull(skb, xdp.data - xdp.data_hard_start); How about do this just after bpf_pro_run_xdp() for XDP_TX too? This is more readable and there's no need to change xmit path. > break; > case XDP_TX: > virtnet_xdp_xmit(vi, rq, &xdp, skb); > @@ -432,6 +442,7 @@ static struct sk_buff *receive_small(struct net_device *dev, > } > rcu_read_unlock(); > > + skb_trim(skb, len); > return skb; > > err_xdp: > @@ -569,7 +580,11 @@ static struct sk_buff *receive_mergeable(struct net_device *dev, > if (unlikely(hdr->hdr.gso_type)) > goto err_xdp; > > + /* Allow consuming headroom but reserve enough space to push > + * the descriptor on if we get an XDP_TX return code. > + */ > data = page_address(xdp_page) + offset; > + xdp.data_hard_start = data - vi->headroom + desc_room; Two possible issues here: 1) If we want to adjust header after linearizing, we should reserve a room for that page, but I don't see any codes for this. 2) If the header has been adjusted, looks like we need change offset value otherwise, page_to_skb() won't build a correct skb for us for XDP_PASS. > xdp.data = data + desc_room; > xdp.data_end = xdp.data + (len - vi->hdr_len); > act = bpf_prog_run_xdp(xdp_prog, &xdp); > @@ -748,20 +763,21 @@ static void receive_buf(struct virtnet_info *vi, struct receive_queue *rq, > static int add_recvbuf_small(struct virtnet_info *vi, struct receive_queue *rq, > gfp_t gfp) > { > + int headroom = GOOD_PACKET_LEN + vi->headroom; > struct sk_buff *skb; > struct virtio_net_hdr_mrg_rxbuf *hdr; > int err; > > - skb = __netdev_alloc_skb_ip_align(vi->dev, GOOD_PACKET_LEN, gfp); > + skb = __netdev_alloc_skb_ip_align(vi->dev, headroom, gfp); > if (unlikely(!skb)) > return -ENOMEM; > > - skb_put(skb, GOOD_PACKET_LEN); > + skb_put(skb, headroom); > > hdr = skb_vnet_hdr(skb); > sg_init_table(rq->sg, 2); > sg_set_buf(rq->sg, hdr, vi->hdr_len); > - skb_to_sgvec(skb, rq->sg + 1, 0, skb->len); > + skb_to_sgvec(skb, rq->sg + 1, vi->headroom, skb->len - vi->headroom); > > err = virtqueue_add_inbuf(rq->vq, rq->sg, 2, skb, gfp); > if (err < 0) > @@ -829,24 +845,27 @@ static unsigned int get_mergeable_buf_len(struct ewma_pkt_len *avg_pkt_len) > return ALIGN(len, MERGEABLE_BUFFER_ALIGN); > } > > -static int add_recvbuf_mergeable(struct receive_queue *rq, gfp_t gfp) > +static int add_recvbuf_mergeable(struct virtnet_info *vi, > + struct receive_queue *rq, gfp_t gfp) > { > struct page_frag *alloc_frag = &rq->alloc_frag; > + unsigned int headroom = vi->headroom; > char *buf; > unsigned long ctx; > int err; > unsigned int len, hole; > > len = get_mergeable_buf_len(&rq->mrg_avg_pkt_len); > - if (unlikely(!skb_page_frag_refill(len, alloc_frag, gfp))) > + if (unlikely(!skb_page_frag_refill(len + headroom, alloc_frag, gfp))) > return -ENOMEM; > > buf = (char *)page_address(alloc_frag->page) + alloc_frag->offset; > + buf += headroom; /* advance address leaving hole at front of pkt */ > ctx = mergeable_buf_to_ctx(buf, len); > get_page(alloc_frag->page); > - alloc_frag->offset += len; > + alloc_frag->offset += len + headroom; > hole = alloc_frag->size - alloc_frag->offset; > - if (hole < len) { > + if (hole < len + headroom) { > /* To avoid internal fragmentation, if there is very likely not > * enough space for another buffer, add the remaining space to > * the current buffer. This extra space is not included in > @@ -880,7 +899,7 @@ static bool try_fill_recv(struct virtnet_info *vi, struct receive_queue *rq, > gfp |= __GFP_COLD; > do { > if (vi->mergeable_rx_bufs) > - err = add_recvbuf_mergeable(rq, gfp); > + err = add_recvbuf_mergeable(vi, rq, gfp); > else if (vi->big_packets) > err = add_recvbuf_big(vi, rq, gfp); > else > @@ -1675,12 +1694,90 @@ static void virtnet_init_settings(struct net_device *dev) > .set_settings = virtnet_set_settings, > }; > > +#define VIRTIO_XDP_HEADROOM 256 > + > +static int init_vqs(struct virtnet_info *vi); > +static void remove_vq_common(struct virtnet_info *vi, bool lock); > + > +/* Reset virtio device with RTNL held this is very similar to the > + * freeze()/restore() logic except we need to ensure locking. It is > + * possible that this routine may fail and leave the driver in a > + * failed state. However assuming the driver negotiated correctly > + * at probe time we _should_ be able to (re)negotiate driver again. > + */ Instead of duplicate codes and export helpers, why not use virtio_device_freeze()/virtio_device_restore()? For rtnl_lock in restore, you can probably avoid it be checking rtnl_is_locked() before? > +static int virtnet_xdp_reset(struct virtnet_info *vi) > +{ > + struct virtio_device *vdev = vi->vdev; > + unsigned int status; > + int i, ret; > + > + /* Disable and unwind rings */ > + virtio_config_disable(vdev); > + vdev->failed = vdev->config->get_status(vdev) & VIRTIO_CONFIG_S_FAILED; > + > + netif_device_detach(vi->dev); > + cancel_delayed_work_sync(&vi->refill); > + if (netif_running(vi->dev)) { > + for (i = 0; i < vi->max_queue_pairs; i++) > + napi_disable(&vi->rq[i].napi); > + } > + > + remove_vq_common(vi, false); > + > + /* Do a reset per virtio spec recommendation */ > + vdev->config->reset(vdev); > + > + /* Acknowledge that we've seen the device. */ > + status = vdev->config->get_status(vdev); > + vdev->config->set_status(vdev, status | VIRTIO_CONFIG_S_ACKNOWLEDGE); > + > + /* Notify driver is up and finalize features per specification. The > + * error code from finalize features is checked here but should not > + * fail because we assume features were previously synced successfully. > + */ > + status = vdev->config->get_status(vdev); > + vdev->config->set_status(vdev, status | VIRTIO_CONFIG_S_DRIVER); > + ret = virtio_finalize_features(vdev); > + if (ret) { > + netdev_warn(vi->dev, "virtio_finalize_features failed during reset aborting\n"); > + goto err; > + } > + > + ret = init_vqs(vi); > + if (ret) { > + netdev_warn(vi->dev, "init_vqs failed during reset aborting\n"); > + goto err; > + } > + virtio_device_ready(vi->vdev); > + > + if (netif_running(vi->dev)) { > + for (i = 0; i < vi->curr_queue_pairs; i++) > + if (!try_fill_recv(vi, &vi->rq[i], GFP_KERNEL)) > + schedule_delayed_work(&vi->refill, 0); > + > + for (i = 0; i < vi->max_queue_pairs; i++) > + virtnet_napi_enable(&vi->rq[i]); > + } > + netif_device_attach(vi->dev); > + /* Finally, tell the device we're all set */ > + status = vdev->config->get_status(vdev); > + vdev->config->set_status(vdev, status | VIRTIO_CONFIG_S_DRIVER_OK); > + virtio_config_enable(vdev); > + > + return 0; > +err: > + status = vdev->config->get_status(vdev); > + vdev->config->set_status(vdev, status | VIRTIO_CONFIG_S_FAILED); > + return ret; > +} [...]
On 17-01-12 11:41 PM, Jason Wang wrote: > > > On 2017年01月13日 10:52, John Fastabend wrote: >> Add support for XDP adjust head by allocating a 256B header region >> that XDP programs can grow into. This is only enabled when a XDP >> program is loaded. >> >> In order to ensure that we do not have to unwind queue headroom push >> queue setup below bpf_prog_add. It reads better to do a prog ref >> unwind vs another queue setup call. >> >> At the moment this code must do a full reset to ensure old buffers >> without headroom on program add or with headroom on program removal >> are not used incorrectly in the datapath. Ideally we would only >> have to disable/enable the RX queues being updated but there is no >> API to do this at the moment in virtio so use the big hammer. In >> practice it is likely not that big of a problem as this will only >> happen when XDP is enabled/disabled changing programs does not >> require the reset. There is some risk that the driver may either >> have an allocation failure or for some reason fail to correctly >> negotiate with the underlying backend in this case the driver will >> be left uninitialized. I have not seen this ever happen on my test >> systems and for what its worth this same failure case can occur >> from probe and other contexts in virtio framework. >> >> Signed-off-by: John Fastabend <john.r.fastabend@intel.com> >> --- >> drivers/net/virtio_net.c | 155 ++++++++++++++++++++++++++++++++++++++++------ >> drivers/virtio/virtio.c | 9 ++- >> include/linux/virtio.h | 3 + >> 3 files changed, 144 insertions(+), 23 deletions(-) >> >> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c >> index 6041828..8b897e7 100644 >> --- a/drivers/net/virtio_net.c >> +++ b/drivers/net/virtio_net.c >> @@ -28,6 +28,7 @@ >> #include <linux/slab.h> >> #include <linux/cpu.h> >> #include <linux/average.h> >> +#include <linux/pci.h> >> #include <net/busy_poll.h> >> static int napi_weight = NAPI_POLL_WEIGHT; >> @@ -159,6 +160,9 @@ struct virtnet_info { >> /* Ethtool settings */ >> u8 duplex; >> u32 speed; >> + >> + /* Headroom allocated in RX Queue */ >> + unsigned int headroom; > > If this could not be changed in anyway, better use a macro instead of a filed > here. And there's even no need to add an extra parameter to > add_recvbuf_mergeable(). OK originally I thought this might be dynamic but I agree no need for it here. > >> }; >> struct padded_vnet_hdr { >> @@ -359,6 +363,7 @@ static void virtnet_xdp_xmit(struct virtnet_info *vi, >> } >> if (vi->mergeable_rx_bufs) { >> + xdp->data -= sizeof(struct virtio_net_hdr_mrg_rxbuf); > > Fail to understand why this is needed. We should have excluded vnet header from > xdp->data even before bpf_prog_run_xdp(). > >> /* Zero header and leave csum up to XDP layers */ >> hdr = xdp->data; >> memset(hdr, 0, vi->hdr_len); >> @@ -375,7 +380,9 @@ static void virtnet_xdp_xmit(struct virtnet_info *vi, >> num_sg = 2; >> sg_init_table(sq->sg, 2); >> sg_set_buf(sq->sg, hdr, vi->hdr_len); >> - skb_to_sgvec(skb, sq->sg + 1, 0, skb->len); >> + skb_to_sgvec(skb, sq->sg + 1, >> + xdp->data - xdp->data_hard_start, >> + xdp->data_end - xdp->data); >> } >> err = virtqueue_add_outbuf(sq->vq, sq->sg, num_sg, >> data, GFP_ATOMIC); >> @@ -401,7 +408,6 @@ static struct sk_buff *receive_small(struct net_device *dev, >> struct bpf_prog *xdp_prog; >> len -= vi->hdr_len; >> - skb_trim(skb, len); >> rcu_read_lock(); >> xdp_prog = rcu_dereference(rq->xdp_prog); >> @@ -413,11 +419,15 @@ static struct sk_buff *receive_small(struct net_device >> *dev, >> if (unlikely(hdr->hdr.gso_type || hdr->hdr.flags)) >> goto err_xdp; >> - xdp.data = skb->data; >> + xdp.data_hard_start = skb->data; >> + xdp.data = skb->data + vi->headroom; >> xdp.data_end = xdp.data + len; >> act = bpf_prog_run_xdp(xdp_prog, &xdp); >> switch (act) { >> case XDP_PASS: >> + /* Recalculate length in case bpf program changed it */ >> + len = xdp.data_end - xdp.data; >> + __skb_pull(skb, xdp.data - xdp.data_hard_start); > > How about do this just after bpf_pro_run_xdp() for XDP_TX too? This is more > readable and there's no need to change xmit path. Agreed will do. > >> break; >> case XDP_TX: >> virtnet_xdp_xmit(vi, rq, &xdp, skb); >> @@ -432,6 +442,7 @@ static struct sk_buff *receive_small(struct net_device *dev, >> } >> rcu_read_unlock(); >> + skb_trim(skb, len); >> return skb; >> err_xdp: >> @@ -569,7 +580,11 @@ static struct sk_buff *receive_mergeable(struct >> net_device *dev, >> if (unlikely(hdr->hdr.gso_type)) >> goto err_xdp; >> + /* Allow consuming headroom but reserve enough space to push >> + * the descriptor on if we get an XDP_TX return code. >> + */ >> data = page_address(xdp_page) + offset; >> + xdp.data_hard_start = data - vi->headroom + desc_room; > > Two possible issues here: > > 1) If we want to adjust header after linearizing, we should reserve a room for > that page, but I don't see any codes for this. > 2) If the header has been adjusted, looks like we need change offset value > otherwise, page_to_skb() won't build a correct skb for us for XDP_PASS. > Both correct thanks. I'll add a couple sample programs to catch this as well. >> xdp.data = data + desc_room; >> xdp.data_end = xdp.data + (len - vi->hdr_len); >> act = bpf_prog_run_xdp(xdp_prog, &xdp); >> @@ -748,20 +763,21 @@ static void receive_buf(struct virtnet_info *vi, struct >> receive_queue *rq, >> static int add_recvbuf_small(struct virtnet_info *vi, struct receive_queue *rq, >> gfp_t gfp) >> { >> + int headroom = GOOD_PACKET_LEN + vi->headroom; >> struct sk_buff *skb; >> struct virtio_net_hdr_mrg_rxbuf *hdr; >> int err; >> - skb = __netdev_alloc_skb_ip_align(vi->dev, GOOD_PACKET_LEN, gfp); >> + skb = __netdev_alloc_skb_ip_align(vi->dev, headroom, gfp); >> if (unlikely(!skb)) >> return -ENOMEM; >> - skb_put(skb, GOOD_PACKET_LEN); >> + skb_put(skb, headroom); >> hdr = skb_vnet_hdr(skb); >> sg_init_table(rq->sg, 2); >> sg_set_buf(rq->sg, hdr, vi->hdr_len); >> - skb_to_sgvec(skb, rq->sg + 1, 0, skb->len); >> + skb_to_sgvec(skb, rq->sg + 1, vi->headroom, skb->len - vi->headroom); >> err = virtqueue_add_inbuf(rq->vq, rq->sg, 2, skb, gfp); >> if (err < 0) >> @@ -829,24 +845,27 @@ static unsigned int get_mergeable_buf_len(struct >> ewma_pkt_len *avg_pkt_len) >> return ALIGN(len, MERGEABLE_BUFFER_ALIGN); >> } >> -static int add_recvbuf_mergeable(struct receive_queue *rq, gfp_t gfp) >> +static int add_recvbuf_mergeable(struct virtnet_info *vi, >> + struct receive_queue *rq, gfp_t gfp) >> { >> struct page_frag *alloc_frag = &rq->alloc_frag; >> + unsigned int headroom = vi->headroom; >> char *buf; >> unsigned long ctx; >> int err; >> unsigned int len, hole; >> len = get_mergeable_buf_len(&rq->mrg_avg_pkt_len); >> - if (unlikely(!skb_page_frag_refill(len, alloc_frag, gfp))) >> + if (unlikely(!skb_page_frag_refill(len + headroom, alloc_frag, gfp))) >> return -ENOMEM; >> buf = (char *)page_address(alloc_frag->page) + alloc_frag->offset; >> + buf += headroom; /* advance address leaving hole at front of pkt */ >> ctx = mergeable_buf_to_ctx(buf, len); >> get_page(alloc_frag->page); >> - alloc_frag->offset += len; >> + alloc_frag->offset += len + headroom; >> hole = alloc_frag->size - alloc_frag->offset; >> - if (hole < len) { >> + if (hole < len + headroom) { >> /* To avoid internal fragmentation, if there is very likely not >> * enough space for another buffer, add the remaining space to >> * the current buffer. This extra space is not included in >> @@ -880,7 +899,7 @@ static bool try_fill_recv(struct virtnet_info *vi, struct >> receive_queue *rq, >> gfp |= __GFP_COLD; >> do { >> if (vi->mergeable_rx_bufs) >> - err = add_recvbuf_mergeable(rq, gfp); >> + err = add_recvbuf_mergeable(vi, rq, gfp); >> else if (vi->big_packets) >> err = add_recvbuf_big(vi, rq, gfp); >> else >> @@ -1675,12 +1694,90 @@ static void virtnet_init_settings(struct net_device *dev) >> .set_settings = virtnet_set_settings, >> }; >> +#define VIRTIO_XDP_HEADROOM 256 >> + >> +static int init_vqs(struct virtnet_info *vi); >> +static void remove_vq_common(struct virtnet_info *vi, bool lock); >> + >> +/* Reset virtio device with RTNL held this is very similar to the >> + * freeze()/restore() logic except we need to ensure locking. It is >> + * possible that this routine may fail and leave the driver in a >> + * failed state. However assuming the driver negotiated correctly >> + * at probe time we _should_ be able to (re)negotiate driver again. >> + */ > > Instead of duplicate codes and export helpers, why not use > virtio_device_freeze()/virtio_device_restore()? For rtnl_lock in restore, you > can probably avoid it be checking rtnl_is_locked() before? freeze/restore does virtnet_cpu_notif_* work that is not needed in this case. But the overhead here is maybe minimal. Michael wanted to create a generic virtio_reset() so let me give that a try and that should clean this up as well. .John > >> +static int virtnet_xdp_reset(struct virtnet_info *vi) >> +{ >> + struct virtio_device *vdev = vi->vdev; >> + unsigned int status; >> + int i, ret; >> + >> + /* Disable and unwind rings */ >> + virtio_config_disable(vdev); >> + vdev->failed = vdev->config->get_status(vdev) & VIRTIO_CONFIG_S_FAILED; >> + >> + netif_device_detach(vi->dev); >> + cancel_delayed_work_sync(&vi->refill); >> + if (netif_running(vi->dev)) { >> + for (i = 0; i < vi->max_queue_pairs; i++) >> + napi_disable(&vi->rq[i].napi); >> + } >> + >> + remove_vq_common(vi, false); >> + >> + /* Do a reset per virtio spec recommendation */ >> + vdev->config->reset(vdev); >> + >> + /* Acknowledge that we've seen the device. */ >> + status = vdev->config->get_status(vdev); >> + vdev->config->set_status(vdev, status | VIRTIO_CONFIG_S_ACKNOWLEDGE); >> + >> + /* Notify driver is up and finalize features per specification. The >> + * error code from finalize features is checked here but should not >> + * fail because we assume features were previously synced successfully. >> + */ >> + status = vdev->config->get_status(vdev); >> + vdev->config->set_status(vdev, status | VIRTIO_CONFIG_S_DRIVER); >> + ret = virtio_finalize_features(vdev); >> + if (ret) { >> + netdev_warn(vi->dev, "virtio_finalize_features failed during reset >> aborting\n"); >> + goto err; >> + } >> + >> + ret = init_vqs(vi); >> + if (ret) { >> + netdev_warn(vi->dev, "init_vqs failed during reset aborting\n"); >> + goto err; >> + } >> + virtio_device_ready(vi->vdev); >> + >> + if (netif_running(vi->dev)) { >> + for (i = 0; i < vi->curr_queue_pairs; i++) >> + if (!try_fill_recv(vi, &vi->rq[i], GFP_KERNEL)) >> + schedule_delayed_work(&vi->refill, 0); >> + >> + for (i = 0; i < vi->max_queue_pairs; i++) >> + virtnet_napi_enable(&vi->rq[i]); >> + } >> + netif_device_attach(vi->dev); >> + /* Finally, tell the device we're all set */ >> + status = vdev->config->get_status(vdev); >> + vdev->config->set_status(vdev, status | VIRTIO_CONFIG_S_DRIVER_OK); >> + virtio_config_enable(vdev); >> + >> + return 0; >> +err: >> + status = vdev->config->get_status(vdev); >> + vdev->config->set_status(vdev, status | VIRTIO_CONFIG_S_FAILED); >> + return ret; >> +} > > [...]
On 17-01-13 12:08 PM, John Fastabend wrote: > On 17-01-12 11:41 PM, Jason Wang wrote: >> >> >> On 2017年01月13日 10:52, John Fastabend wrote: >>> Add support for XDP adjust head by allocating a 256B header region >>> that XDP programs can grow into. This is only enabled when a XDP >>> program is loaded. >>> >>> In order to ensure that we do not have to unwind queue headroom push >>> queue setup below bpf_prog_add. It reads better to do a prog ref >>> unwind vs another queue setup call. >>> >>> At the moment this code must do a full reset to ensure old buffers >>> without headroom on program add or with headroom on program removal >>> are not used incorrectly in the datapath. Ideally we would only >>> have to disable/enable the RX queues being updated but there is no >>> API to do this at the moment in virtio so use the big hammer. In >>> practice it is likely not that big of a problem as this will only >>> happen when XDP is enabled/disabled changing programs does not >>> require the reset. There is some risk that the driver may either >>> have an allocation failure or for some reason fail to correctly >>> negotiate with the underlying backend in this case the driver will >>> be left uninitialized. I have not seen this ever happen on my test >>> systems and for what its worth this same failure case can occur >>> from probe and other contexts in virtio framework. >>> >>> Signed-off-by: John Fastabend <john.r.fastabend@intel.com> >>> --- >>> drivers/net/virtio_net.c | 155 ++++++++++++++++++++++++++++++++++++++++------ >>> drivers/virtio/virtio.c | 9 ++- >>> include/linux/virtio.h | 3 + >>> 3 files changed, 144 insertions(+), 23 deletions(-) >>> >>> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c >>> index 6041828..8b897e7 100644 >>> --- a/drivers/net/virtio_net.c >>> +++ b/drivers/net/virtio_net.c >>> @@ -28,6 +28,7 @@ >>> #include <linux/slab.h> >>> #include <linux/cpu.h> >>> #include <linux/average.h> >>> +#include <linux/pci.h> >>> #include <net/busy_poll.h> >>> static int napi_weight = NAPI_POLL_WEIGHT; >>> @@ -159,6 +160,9 @@ struct virtnet_info { >>> /* Ethtool settings */ >>> u8 duplex; >>> u32 speed; >>> + >>> + /* Headroom allocated in RX Queue */ >>> + unsigned int headroom; >> >> If this could not be changed in anyway, better use a macro instead of a filed >> here. And there's even no need to add an extra parameter to >> add_recvbuf_mergeable(). > > OK originally I thought this might be dynamic but I agree no need > for it here. > Well there is a bit of an order of operation issue that means we need at least some bit here to tell us an enablement is pending. The problem is when we do the reset we need to know that headroom for XDP is needed. But we can't use the xdp_prog values because xdp_prog can not be added on an device that is up without headroom otherwise the program could fail. Plus reset via freeze/restore tears these structures down and rebuilds them. How about a boolean bit here instead of an unsigned int, 'bool xdp_headroom_needed' seems better than an int. Thanks, John
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index 6041828..8b897e7 100644 --- a/drivers/net/virtio_net.c +++ b/drivers/net/virtio_net.c @@ -28,6 +28,7 @@ #include <linux/slab.h> #include <linux/cpu.h> #include <linux/average.h> +#include <linux/pci.h> #include <net/busy_poll.h> static int napi_weight = NAPI_POLL_WEIGHT; @@ -159,6 +160,9 @@ struct virtnet_info { /* Ethtool settings */ u8 duplex; u32 speed; + + /* Headroom allocated in RX Queue */ + unsigned int headroom; }; struct padded_vnet_hdr { @@ -359,6 +363,7 @@ static void virtnet_xdp_xmit(struct virtnet_info *vi, } if (vi->mergeable_rx_bufs) { + xdp->data -= sizeof(struct virtio_net_hdr_mrg_rxbuf); /* Zero header and leave csum up to XDP layers */ hdr = xdp->data; memset(hdr, 0, vi->hdr_len); @@ -375,7 +380,9 @@ static void virtnet_xdp_xmit(struct virtnet_info *vi, num_sg = 2; sg_init_table(sq->sg, 2); sg_set_buf(sq->sg, hdr, vi->hdr_len); - skb_to_sgvec(skb, sq->sg + 1, 0, skb->len); + skb_to_sgvec(skb, sq->sg + 1, + xdp->data - xdp->data_hard_start, + xdp->data_end - xdp->data); } err = virtqueue_add_outbuf(sq->vq, sq->sg, num_sg, data, GFP_ATOMIC); @@ -401,7 +408,6 @@ static struct sk_buff *receive_small(struct net_device *dev, struct bpf_prog *xdp_prog; len -= vi->hdr_len; - skb_trim(skb, len); rcu_read_lock(); xdp_prog = rcu_dereference(rq->xdp_prog); @@ -413,11 +419,15 @@ static struct sk_buff *receive_small(struct net_device *dev, if (unlikely(hdr->hdr.gso_type || hdr->hdr.flags)) goto err_xdp; - xdp.data = skb->data; + xdp.data_hard_start = skb->data; + xdp.data = skb->data + vi->headroom; xdp.data_end = xdp.data + len; act = bpf_prog_run_xdp(xdp_prog, &xdp); switch (act) { case XDP_PASS: + /* Recalculate length in case bpf program changed it */ + len = xdp.data_end - xdp.data; + __skb_pull(skb, xdp.data - xdp.data_hard_start); break; case XDP_TX: virtnet_xdp_xmit(vi, rq, &xdp, skb); @@ -432,6 +442,7 @@ static struct sk_buff *receive_small(struct net_device *dev, } rcu_read_unlock(); + skb_trim(skb, len); return skb; err_xdp: @@ -569,7 +580,11 @@ static struct sk_buff *receive_mergeable(struct net_device *dev, if (unlikely(hdr->hdr.gso_type)) goto err_xdp; + /* Allow consuming headroom but reserve enough space to push + * the descriptor on if we get an XDP_TX return code. + */ data = page_address(xdp_page) + offset; + xdp.data_hard_start = data - vi->headroom + desc_room; xdp.data = data + desc_room; xdp.data_end = xdp.data + (len - vi->hdr_len); act = bpf_prog_run_xdp(xdp_prog, &xdp); @@ -748,20 +763,21 @@ static void receive_buf(struct virtnet_info *vi, struct receive_queue *rq, static int add_recvbuf_small(struct virtnet_info *vi, struct receive_queue *rq, gfp_t gfp) { + int headroom = GOOD_PACKET_LEN + vi->headroom; struct sk_buff *skb; struct virtio_net_hdr_mrg_rxbuf *hdr; int err; - skb = __netdev_alloc_skb_ip_align(vi->dev, GOOD_PACKET_LEN, gfp); + skb = __netdev_alloc_skb_ip_align(vi->dev, headroom, gfp); if (unlikely(!skb)) return -ENOMEM; - skb_put(skb, GOOD_PACKET_LEN); + skb_put(skb, headroom); hdr = skb_vnet_hdr(skb); sg_init_table(rq->sg, 2); sg_set_buf(rq->sg, hdr, vi->hdr_len); - skb_to_sgvec(skb, rq->sg + 1, 0, skb->len); + skb_to_sgvec(skb, rq->sg + 1, vi->headroom, skb->len - vi->headroom); err = virtqueue_add_inbuf(rq->vq, rq->sg, 2, skb, gfp); if (err < 0) @@ -829,24 +845,27 @@ static unsigned int get_mergeable_buf_len(struct ewma_pkt_len *avg_pkt_len) return ALIGN(len, MERGEABLE_BUFFER_ALIGN); } -static int add_recvbuf_mergeable(struct receive_queue *rq, gfp_t gfp) +static int add_recvbuf_mergeable(struct virtnet_info *vi, + struct receive_queue *rq, gfp_t gfp) { struct page_frag *alloc_frag = &rq->alloc_frag; + unsigned int headroom = vi->headroom; char *buf; unsigned long ctx; int err; unsigned int len, hole; len = get_mergeable_buf_len(&rq->mrg_avg_pkt_len); - if (unlikely(!skb_page_frag_refill(len, alloc_frag, gfp))) + if (unlikely(!skb_page_frag_refill(len + headroom, alloc_frag, gfp))) return -ENOMEM; buf = (char *)page_address(alloc_frag->page) + alloc_frag->offset; + buf += headroom; /* advance address leaving hole at front of pkt */ ctx = mergeable_buf_to_ctx(buf, len); get_page(alloc_frag->page); - alloc_frag->offset += len; + alloc_frag->offset += len + headroom; hole = alloc_frag->size - alloc_frag->offset; - if (hole < len) { + if (hole < len + headroom) { /* To avoid internal fragmentation, if there is very likely not * enough space for another buffer, add the remaining space to * the current buffer. This extra space is not included in @@ -880,7 +899,7 @@ static bool try_fill_recv(struct virtnet_info *vi, struct receive_queue *rq, gfp |= __GFP_COLD; do { if (vi->mergeable_rx_bufs) - err = add_recvbuf_mergeable(rq, gfp); + err = add_recvbuf_mergeable(vi, rq, gfp); else if (vi->big_packets) err = add_recvbuf_big(vi, rq, gfp); else @@ -1675,12 +1694,90 @@ static void virtnet_init_settings(struct net_device *dev) .set_settings = virtnet_set_settings, }; +#define VIRTIO_XDP_HEADROOM 256 + +static int init_vqs(struct virtnet_info *vi); +static void remove_vq_common(struct virtnet_info *vi, bool lock); + +/* Reset virtio device with RTNL held this is very similar to the + * freeze()/restore() logic except we need to ensure locking. It is + * possible that this routine may fail and leave the driver in a + * failed state. However assuming the driver negotiated correctly + * at probe time we _should_ be able to (re)negotiate driver again. + */ +static int virtnet_xdp_reset(struct virtnet_info *vi) +{ + struct virtio_device *vdev = vi->vdev; + unsigned int status; + int i, ret; + + /* Disable and unwind rings */ + virtio_config_disable(vdev); + vdev->failed = vdev->config->get_status(vdev) & VIRTIO_CONFIG_S_FAILED; + + netif_device_detach(vi->dev); + cancel_delayed_work_sync(&vi->refill); + if (netif_running(vi->dev)) { + for (i = 0; i < vi->max_queue_pairs; i++) + napi_disable(&vi->rq[i].napi); + } + + remove_vq_common(vi, false); + + /* Do a reset per virtio spec recommendation */ + vdev->config->reset(vdev); + + /* Acknowledge that we've seen the device. */ + status = vdev->config->get_status(vdev); + vdev->config->set_status(vdev, status | VIRTIO_CONFIG_S_ACKNOWLEDGE); + + /* Notify driver is up and finalize features per specification. The + * error code from finalize features is checked here but should not + * fail because we assume features were previously synced successfully. + */ + status = vdev->config->get_status(vdev); + vdev->config->set_status(vdev, status | VIRTIO_CONFIG_S_DRIVER); + ret = virtio_finalize_features(vdev); + if (ret) { + netdev_warn(vi->dev, "virtio_finalize_features failed during reset aborting\n"); + goto err; + } + + ret = init_vqs(vi); + if (ret) { + netdev_warn(vi->dev, "init_vqs failed during reset aborting\n"); + goto err; + } + virtio_device_ready(vi->vdev); + + if (netif_running(vi->dev)) { + for (i = 0; i < vi->curr_queue_pairs; i++) + if (!try_fill_recv(vi, &vi->rq[i], GFP_KERNEL)) + schedule_delayed_work(&vi->refill, 0); + + for (i = 0; i < vi->max_queue_pairs; i++) + virtnet_napi_enable(&vi->rq[i]); + } + netif_device_attach(vi->dev); + /* Finally, tell the device we're all set */ + status = vdev->config->get_status(vdev); + vdev->config->set_status(vdev, status | VIRTIO_CONFIG_S_DRIVER_OK); + virtio_config_enable(vdev); + + return 0; +err: + status = vdev->config->get_status(vdev); + vdev->config->set_status(vdev, status | VIRTIO_CONFIG_S_FAILED); + return ret; +} + static int virtnet_xdp_set(struct net_device *dev, struct bpf_prog *prog) { unsigned long int max_sz = PAGE_SIZE - sizeof(struct padded_vnet_hdr); struct virtnet_info *vi = netdev_priv(dev); struct bpf_prog *old_prog; u16 xdp_qp = 0, curr_qp; + unsigned int old_hr; int i, err; if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_TSO4) || @@ -1712,18 +1809,31 @@ static int virtnet_xdp_set(struct net_device *dev, struct bpf_prog *prog) return -ENOMEM; } - err = virtnet_set_queues(vi, curr_qp + xdp_qp); - if (err) { - dev_warn(&dev->dev, "XDP Device queue allocation failure.\n"); - return err; - } - + old_hr = vi->headroom; if (prog) { prog = bpf_prog_add(prog, vi->max_queue_pairs - 1); - if (IS_ERR(prog)) { - virtnet_set_queues(vi, curr_qp); + if (IS_ERR(prog)) return PTR_ERR(prog); - } + vi->headroom = VIRTIO_XDP_HEADROOM; + } else { + vi->headroom = 0; + } + + /* Changing the headroom in buffers is a disruptive operation because + * existing buffers must be flushed and reallocated. This will happen + * when a xdp program is initially added or xdp is disabled by removing + * the xdp program. + */ + if (old_hr != vi->headroom) { + err = virtnet_xdp_reset(vi); + if (err) + goto err_reset; + } + + err = virtnet_set_queues(vi, curr_qp + xdp_qp); + if (err) { + dev_warn(&dev->dev, "XDP Device queue allocation failure.\n"); + goto err_reset; } vi->xdp_queue_pairs = xdp_qp; @@ -1737,6 +1847,11 @@ static int virtnet_xdp_set(struct net_device *dev, struct bpf_prog *prog) } return 0; +err_reset: + if (prog) + bpf_prog_sub(prog, vi->max_queue_pairs - 1); + vi->headroom = old_hr; + return err; } static bool virtnet_xdp_query(struct net_device *dev) diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c index 7062bb0..0e922b9 100644 --- a/drivers/virtio/virtio.c +++ b/drivers/virtio/virtio.c @@ -145,14 +145,15 @@ void virtio_config_changed(struct virtio_device *dev) } EXPORT_SYMBOL_GPL(virtio_config_changed); -static void virtio_config_disable(struct virtio_device *dev) +void virtio_config_disable(struct virtio_device *dev) { spin_lock_irq(&dev->config_lock); dev->config_enabled = false; spin_unlock_irq(&dev->config_lock); } +EXPORT_SYMBOL_GPL(virtio_config_disable); -static void virtio_config_enable(struct virtio_device *dev) +void virtio_config_enable(struct virtio_device *dev) { spin_lock_irq(&dev->config_lock); dev->config_enabled = true; @@ -161,8 +162,9 @@ static void virtio_config_enable(struct virtio_device *dev) dev->config_change_pending = false; spin_unlock_irq(&dev->config_lock); } +EXPORT_SYMBOL_GPL(virtio_config_enable); -static int virtio_finalize_features(struct virtio_device *dev) +int virtio_finalize_features(struct virtio_device *dev) { int ret = dev->config->finalize_features(dev); unsigned status; @@ -182,6 +184,7 @@ static int virtio_finalize_features(struct virtio_device *dev) } return 0; } +EXPORT_SYMBOL_GPL(virtio_finalize_features); static int virtio_dev_probe(struct device *_d) { diff --git a/include/linux/virtio.h b/include/linux/virtio.h index d5eb547..eac8f05 100644 --- a/include/linux/virtio.h +++ b/include/linux/virtio.h @@ -137,6 +137,9 @@ static inline struct virtio_device *dev_to_virtio(struct device *_dev) void virtio_break_device(struct virtio_device *dev); +void virtio_config_disable(struct virtio_device *dev); +void virtio_config_enable(struct virtio_device *dev); +int virtio_finalize_features(struct virtio_device *dev); void virtio_config_changed(struct virtio_device *dev); #ifdef CONFIG_PM_SLEEP int virtio_device_freeze(struct virtio_device *dev);
Add support for XDP adjust head by allocating a 256B header region that XDP programs can grow into. This is only enabled when a XDP program is loaded. In order to ensure that we do not have to unwind queue headroom push queue setup below bpf_prog_add. It reads better to do a prog ref unwind vs another queue setup call. At the moment this code must do a full reset to ensure old buffers without headroom on program add or with headroom on program removal are not used incorrectly in the datapath. Ideally we would only have to disable/enable the RX queues being updated but there is no API to do this at the moment in virtio so use the big hammer. In practice it is likely not that big of a problem as this will only happen when XDP is enabled/disabled changing programs does not require the reset. There is some risk that the driver may either have an allocation failure or for some reason fail to correctly negotiate with the underlying backend in this case the driver will be left uninitialized. I have not seen this ever happen on my test systems and for what its worth this same failure case can occur from probe and other contexts in virtio framework. Signed-off-by: John Fastabend <john.r.fastabend@intel.com> --- drivers/net/virtio_net.c | 155 ++++++++++++++++++++++++++++++++++++++++------ drivers/virtio/virtio.c | 9 ++- include/linux/virtio.h | 3 + 3 files changed, 144 insertions(+), 23 deletions(-)