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virtio_net: Differentiate sk_buff and xdp_frame on freeing 

We do not reset or free up unused buffers when enabling/disabling XDP,
so it can happen that xdp_frames are freed after disabling XDP or
sk_buffs are freed after enabling XDP on xdp tx queues.
Thus we need to handle both forms (xdp_frames and sk_buffs) regardless
of XDP setting.
One way to trigger this problem is to disable XDP when napi_tx is
enabled. In that case, virtnet_xdp_set() calls virtnet_napi_enable()
which kicks NAPI. The NAPI handler will call virtnet_poll_cleantx()
which invokes free_old_xmit_skbs() for queues which have been used by
XDP.

Note that even with this change we need to keep skipping
free_old_xmit_skbs() from NAPI handlers when XDP is enabled, because XDP
tx queues do not aquire queue locks.

- v2: Use napi_consume_skb() instead of dev_consume_skb_any()

Fixes: 4941d472bf ("virtio-net: do not reset during XDP set")
Signed-off-by: Toshiaki Makita <makita.toshiaki@lab.ntt.co.jp>
Acked-by: Jason Wang <jasowang@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Toshiaki Makita 2019-01-29 09:45:59 +09:00 committed by David S. Miller
parent 07b344f494
commit 5050471d35
1 changed files with 42 additions and 12 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

54
drivers/net/virtio_net.c
View File

@ -57,6 +57,8 @@ module_param(napi_tx, bool, 0644);
#define VIRTIO_XDP_TX BIT(0)
#define VIRTIO_XDP_REDIR BIT(1)
#define VIRTIO_XDP_FLAG BIT(0)
/* RX packet size EWMA. The average packet size is used to determine the packet
* buffer size when refilling RX rings. As the entire RX ring may be refilled
* at once, the weight is chosen so that the EWMA will be insensitive to short-
@ -252,6 +254,21 @@ struct padded_vnet_hdr {
char padding[4];
};
static bool is_xdp_frame(void *ptr)
{
return (unsigned long)ptr & VIRTIO_XDP_FLAG;
}
static void *xdp_to_ptr(struct xdp_frame *ptr)
{
return (void *)((unsigned long)ptr | VIRTIO_XDP_FLAG);
}
static struct xdp_frame *ptr_to_xdp(void *ptr)
{
return (struct xdp_frame *)((unsigned long)ptr & ~VIRTIO_XDP_FLAG);
}
/* Converting between virtqueue no. and kernel tx/rx queue no.
* 0:rx0 1:tx0 2:rx1 3:tx1 ... 2N:rxN 2N+1:txN 2N+2:cvq
*/
@ -462,7 +479,8 @@ static int __virtnet_xdp_xmit_one(struct virtnet_info *vi,
sg_init_one(sq->sg, xdpf->data, xdpf->len);
err = virtqueue_add_outbuf(sq->vq, sq->sg, 1, xdpf, GFP_ATOMIC);
err = virtqueue_add_outbuf(sq->vq, sq->sg, 1, xdp_to_ptr(xdpf),
GFP_ATOMIC);
if (unlikely(err))
return -ENOSPC; /* Caller handle free/refcnt */
@ -482,13 +500,13 @@ static int virtnet_xdp_xmit(struct net_device *dev,
{
struct virtnet_info *vi = netdev_priv(dev);
struct receive_queue *rq = vi->rq;
struct xdp_frame *xdpf_sent;
struct bpf_prog *xdp_prog;
struct send_queue *sq;
unsigned int len;
int drops = 0;
int kicks = 0;
int ret, err;
void *ptr;
int i;
/* Only allow ndo_xdp_xmit if XDP is loaded on dev, as this
@ -507,8 +525,12 @@ static int virtnet_xdp_xmit(struct net_device *dev,
}
/* Free up any pending old buffers before queueing new ones. */
while ((xdpf_sent = virtqueue_get_buf(sq->vq, &len)) != NULL)
xdp_return_frame(xdpf_sent);
while ((ptr = virtqueue_get_buf(sq->vq, &len)) != NULL) {
if (likely(is_xdp_frame(ptr)))
xdp_return_frame(ptr_to_xdp(ptr));
else
napi_consume_skb(ptr, false);
}
for (i = 0; i < n; i++) {
struct xdp_frame *xdpf = frames[i];
@ -1329,18 +1351,26 @@ static int virtnet_receive(struct receive_queue *rq, int budget,
static void free_old_xmit_skbs(struct send_queue *sq, bool in_napi)
{
struct sk_buff *skb;
unsigned int len;
unsigned int packets = 0;
unsigned int bytes = 0;
void *ptr;
while ((skb = virtqueue_get_buf(sq->vq, &len)) != NULL) {
pr_debug("Sent skb %p\n", skb);
while ((ptr = virtqueue_get_buf(sq->vq, &len)) != NULL) {
if (likely(!is_xdp_frame(ptr))) {
struct sk_buff *skb = ptr;
bytes += skb->len;
pr_debug("Sent skb %p\n", skb);
bytes += skb->len;
napi_consume_skb(skb, in_napi);
} else {
struct xdp_frame *frame = ptr_to_xdp(ptr);
bytes += frame->len;
xdp_return_frame(frame);
}
packets++;
napi_consume_skb(skb, in_napi);
}
/* Avoid overhead when no packets have been processed
@ -2666,10 +2696,10 @@ static void free_unused_bufs(struct virtnet_info *vi)
for (i = 0; i < vi->max_queue_pairs; i++) {
struct virtqueue *vq = vi->sq[i].vq;
while ((buf = virtqueue_detach_unused_buf(vq)) != NULL) {
if (!is_xdp_raw_buffer_queue(vi, i))
if (!is_xdp_frame(buf))
dev_kfree_skb(buf);
else
xdp_return_frame(buf);
xdp_return_frame(ptr_to_xdp(buf));
}
}