[PATCH RFC bpf-next 44/52] net, ice: allow XDP prog hot-swapping

Alexander Lobakin
2022-06-28T19:53:47Z

Currently, an interface is always being brought down on
%XDP_SETUP_PROG, no matter if there would be a global configuration
change (no prog -> prog, prog -> no prog) or just a hot-swap (prog
-> prog). That is suboptimal, especially when old_prog == new_prog,
which should be a no-op at all. Moreover, it makes it impossible to
change some aux XDP options on the fly which could be designed to
work like that.
Store &xdp_attachment_info in just one copy inside the VSI
structure, RQs will only have pointers to it. This way we only need
to rewrite it once and xdp_attachment_setup_rcu() now may be used.
Guard NAPI poll routines with RCU read locks to make sure the BPF
prog won't get freed right in the middle of a cycle. Now the old
program will be freed only when all of the rings will use the new
one already. Then do an ifdown->ifup cycle in ::ndo_bpf() only if
absolutely needed (mentioned above), the rest will be completely
safe to do on the go.

Signed-off-by: Alexander Lobakin <alexandr.lobakin@intel.com>
---
drivers/net/ethernet/intel/ice/ice.h | 8 +--
drivers/net/ethernet/intel/ice/ice_lib.c | 4 +-
drivers/net/ethernet/intel/ice/ice_main.c | 61 ++++++++++-------------
drivers/net/ethernet/intel/ice/ice_txrx.c | 11 ++--
drivers/net/ethernet/intel/ice/ice_txrx.h | 2 +-
drivers/net/ethernet/intel/ice/ice_xsk.c | 2 +-
6 files changed, 40 insertions(+), 48 deletions(-)

diff --git a/drivers/net/ethernet/intel/ice/ice.h b/drivers/net/ethernet/intel/ice/ice.h
index 60453b3b8d23..402b71ab48e4 100644
--- a/drivers/net/ethernet/intel/ice/ice.h
+++ b/drivers/net/ethernet/intel/ice/ice.h
@@ -386,7 +386,7 @@ struct ice_vsi {
u16 num_tx_desc;
u16 qset_handle[ICE_MAX_TRAFFIC_CLASS];
struct ice_tc_cfg tc_cfg;
- struct bpf_prog *xdp_prog;
+ struct xdp_attachment_info xdp_info;
struct ice_tx_ring **xdp_rings; /* XDP ring array */
unsigned long *af_xdp_zc_qps; /* tracks AF_XDP ZC enabled qps */
u16 num_xdp_txq; /* Used XDP queues */
@@ -672,7 +672,7 @@ static inline struct ice_pf *ice_netdev_to_pf(struct net_device *netdev)

static inline bool ice_is_xdp_ena_vsi(struct ice_vsi *vsi)
{
- return !!READ_ONCE(vsi->xdp_prog);
+ return !!rcu_access_pointer(vsi->xdp_info.prog_rcu);
}

static inline void ice_set_ring_xdp(struct ice_tx_ring *ring)
@@ -857,8 +857,8 @@ int ice_down(struct ice_vsi *vsi);
int ice_vsi_cfg(struct ice_vsi *vsi);
struct ice_vsi *ice_lb_vsi_setup(struct ice_pf *pf, struct ice_port_info *pi);
int ice_vsi_determine_xdp_res(struct ice_vsi *vsi);
-int ice_prepare_xdp_rings(struct ice_vsi *vsi, struct bpf_prog *prog);
-int ice_destroy_xdp_rings(struct ice_vsi *vsi);
+int ice_prepare_xdp_rings(struct ice_vsi *vsi, struct netdev_bpf *xdp);
+int ice_destroy_xdp_rings(struct ice_vsi *vsi, struct netdev_bpf *xdp);
int
ice_xdp_xmit(struct net_device *dev, int n, struct xdp_frame **frames,
u32 flags);
diff --git a/drivers/net/ethernet/intel/ice/ice_lib.c b/drivers/net/ethernet/intel/ice/ice_lib.c
index b28fb8eacffb..3db1271b5176 100644
--- a/drivers/net/ethernet/intel/ice/ice_lib.c
+++ b/drivers/net/ethernet/intel/ice/ice_lib.c
@@ -3200,7 +3200,7 @@ int ice_vsi_rebuild(struct ice_vsi *vsi, bool init_vsi)
/* return value check can be skipped here, it always returns
* 0 if reset is in progress
*/
- ice_destroy_xdp_rings(vsi);
+ ice_destroy_xdp_rings(vsi, NULL);
ice_vsi_put_qs(vsi);
ice_vsi_clear_rings(vsi);
ice_vsi_free_arrays(vsi);
@@ -3248,7 +3248,7 @@ int ice_vsi_rebuild(struct ice_vsi *vsi, bool init_vsi)
ret = ice_vsi_determine_xdp_res(vsi);
if (ret)
goto err_vectors;
- ret = ice_prepare_xdp_rings(vsi, vsi->xdp_prog);
+ ret = ice_prepare_xdp_rings(vsi, NULL);
if (ret)
goto err_vectors;
}
diff --git a/drivers/net/ethernet/intel/ice/ice_main.c b/drivers/net/ethernet/intel/ice/ice_main.c
index c1ac2f746714..7d049930a0a8 100644
--- a/drivers/net/ethernet/intel/ice/ice_main.c
+++ b/drivers/net/ethernet/intel/ice/ice_main.c
@@ -2603,32 +2603,14 @@ static int ice_xdp_alloc_setup_rings(struct ice_vsi *vsi)
return -ENOMEM;
}

-/**
- * ice_vsi_assign_bpf_prog - set or clear bpf prog pointer on VSI
- * @vsi: VSI to set the bpf prog on
- * @prog: the bpf prog pointer
- */
-static void ice_vsi_assign_bpf_prog(struct ice_vsi *vsi, struct bpf_prog *prog)
-{
- struct bpf_prog *old_prog;
- int i;
-
- old_prog = xchg(&vsi->xdp_prog, prog);
- if (old_prog)
- bpf_prog_put(old_prog);
-
- ice_for_each_rxq(vsi, i)
- WRITE_ONCE(vsi->rx_rings[i]->xdp_prog, vsi->xdp_prog);
-}
-
/**
* ice_prepare_xdp_rings - Allocate, configure and setup Tx rings for XDP
* @vsi: VSI to bring up Tx rings used by XDP
- * @prog: bpf program that will be assigned to VSI
+ * @xdp: &netdev_bpf with XDP program and additional data passed from the stack
*
* Return 0 on success and negative value on error
*/
-int ice_prepare_xdp_rings(struct ice_vsi *vsi, struct bpf_prog *prog)
+int ice_prepare_xdp_rings(struct ice_vsi *vsi, struct netdev_bpf *xdp)
{
u16 max_txqs[ICE_MAX_TRAFFIC_CLASS] = { 0 };
int xdp_rings_rem = vsi->num_xdp_txq;
@@ -2713,8 +2695,8 @@ int ice_prepare_xdp_rings(struct ice_vsi *vsi, struct bpf_prog *prog)
* this is not harmful as dev_xdp_install bumps the refcount
* before calling the op exposed by the driver;
*/
- if (!ice_is_xdp_ena_vsi(vsi))
- ice_vsi_assign_bpf_prog(vsi, prog);
+ if (xdp)
+ xdp_attachment_setup_rcu(&vsi->xdp_info, xdp);

return 0;
clear_xdp_rings:
@@ -2739,11 +2721,12 @@ int ice_prepare_xdp_rings(struct ice_vsi *vsi, struct bpf_prog *prog)
/**
* ice_destroy_xdp_rings - undo the configuration made by ice_prepare_xdp_rings
* @vsi: VSI to remove XDP rings
+ * @xdp: &netdev_bpf with XDP program and additional data passed from the stack
*
* Detach XDP rings from irq vectors, clean up the PF bitmap and free
* resources
*/
-int ice_destroy_xdp_rings(struct ice_vsi *vsi)
+int ice_destroy_xdp_rings(struct ice_vsi *vsi, struct netdev_bpf *xdp)
{
u16 max_txqs[ICE_MAX_TRAFFIC_CLASS] = { 0 };
struct ice_pf *pf = vsi->back;
@@ -2796,7 +2779,11 @@ int ice_destroy_xdp_rings(struct ice_vsi *vsi)
if (ice_is_reset_in_progress(pf->state) || !vsi->q_vectors[0])
return 0;

- ice_vsi_assign_bpf_prog(vsi, NULL);
+ /* Symmetrically to ice_prepare_xdp_rings(), touch XDP program only
+ * when called from ::ndo_bpf().
+ */
+ if (xdp)
+ xdp_attachment_setup_rcu(&vsi->xdp_info, xdp);

/* notify Tx scheduler that we destroyed XDP queues and bring
* back the old number of child nodes
@@ -2853,15 +2840,14 @@ int ice_vsi_determine_xdp_res(struct ice_vsi *vsi)
/**
* ice_xdp_setup_prog - Add or remove XDP eBPF program
* @vsi: VSI to setup XDP for
- * @prog: XDP program
- * @extack: netlink extended ack
+ * @xdp: &netdev_bpf with XDP program and additional data passed from the stack
*/
static int
-ice_xdp_setup_prog(struct ice_vsi *vsi, struct bpf_prog *prog,
- struct netlink_ext_ack *extack)
+ice_xdp_setup_prog(struct ice_vsi *vsi, struct netdev_bpf *xdp)
{
int frame_size = vsi->netdev->mtu + ICE_ETH_PKT_HDR_PAD;
- bool if_running = netif_running(vsi->netdev);
+ struct netlink_ext_ack *extack = xdp->extack;
+ bool restart = false, prog = !!xdp->prog;
int ret = 0, xdp_ring_err = 0;

if (frame_size > vsi->rx_buf_len) {
@@ -2870,12 +2856,15 @@ ice_xdp_setup_prog(struct ice_vsi *vsi, struct bpf_prog *prog,
}

/* need to stop netdev while setting up the program for Rx rings */
- if (if_running && !test_and_set_bit(ICE_VSI_DOWN, vsi->state)) {
+ if (ice_is_xdp_ena_vsi(vsi) != prog && netif_running(vsi->netdev) &&
+ !test_and_set_bit(ICE_VSI_DOWN, vsi->state)) {
ret = ice_down(vsi);
if (ret) {
NL_SET_ERR_MSG_MOD(extack, "Preparing device for XDP attach failed");
return ret;
}
+
+ restart = true;
}

if (!ice_is_xdp_ena_vsi(vsi) && prog) {
@@ -2883,24 +2872,24 @@ ice_xdp_setup_prog(struct ice_vsi *vsi, struct bpf_prog *prog,
if (xdp_ring_err) {
NL_SET_ERR_MSG_MOD(extack, "Not enough Tx resources for XDP");
} else {
- xdp_ring_err = ice_prepare_xdp_rings(vsi, prog);
+ xdp_ring_err = ice_prepare_xdp_rings(vsi, xdp);
if (xdp_ring_err)
NL_SET_ERR_MSG_MOD(extack, "Setting up XDP Tx resources failed");
}
} else if (ice_is_xdp_ena_vsi(vsi) && !prog) {
- xdp_ring_err = ice_destroy_xdp_rings(vsi);
+ xdp_ring_err = ice_destroy_xdp_rings(vsi, xdp);
if (xdp_ring_err)
NL_SET_ERR_MSG_MOD(extack, "Freeing XDP Tx resources failed");
} else {
- /* safe to call even when prog == vsi->xdp_prog as
+ /* safe to call even when prog == vsi->xdp_info.prog as
* dev_xdp_install in net/core/dev.c incremented prog's
* refcount so corresponding bpf_prog_put won't cause
* underflow
*/
- ice_vsi_assign_bpf_prog(vsi, prog);
+ xdp_attachment_setup_rcu(&vsi->xdp_info, xdp);
}

- if (if_running)
+ if (restart)
ret = ice_up(vsi);

if (!ret && prog)
@@ -2940,7 +2929,7 @@ static int ice_xdp(struct net_device *dev, struct netdev_bpf *xdp)

switch (xdp->command) {
case XDP_SETUP_PROG:
- return ice_xdp_setup_prog(vsi, xdp->prog, xdp->extack);
+ return ice_xdp_setup_prog(vsi, xdp);
case XDP_SETUP_XSK_POOL:
return ice_xsk_pool_setup(vsi, xdp->xsk.pool,
xdp->xsk.queue_id);
diff --git a/drivers/net/ethernet/intel/ice/ice_txrx.c b/drivers/net/ethernet/intel/ice/ice_txrx.c
index 3f8b7274ed2f..25383bbf8245 100644
--- a/drivers/net/ethernet/intel/ice/ice_txrx.c
+++ b/drivers/net/ethernet/intel/ice/ice_txrx.c
@@ -454,7 +454,7 @@ void ice_free_rx_ring(struct ice_rx_ring *rx_ring)
if (rx_ring->vsi->type == ICE_VSI_PF)
if (xdp_rxq_info_is_reg(&rx_ring->xdp_rxq))
xdp_rxq_info_unreg(&rx_ring->xdp_rxq);
- rx_ring->xdp_prog = NULL;
+
if (rx_ring->xsk_pool) {
kfree(rx_ring->xdp_buf);
rx_ring->xdp_buf = NULL;
@@ -507,8 +507,7 @@ int ice_setup_rx_ring(struct ice_rx_ring *rx_ring)
rx_ring->next_to_use = 0;
rx_ring->next_to_clean = 0;

- if (ice_is_xdp_ena_vsi(rx_ring->vsi))
- WRITE_ONCE(rx_ring->xdp_prog, rx_ring->vsi->xdp_prog);
+ rx_ring->xdp_info = &rx_ring->vsi->xdp_info;

if (rx_ring->vsi->type == ICE_VSI_PF &&
!xdp_rxq_info_is_reg(&rx_ring->xdp_rxq))
@@ -1123,7 +1122,7 @@ int ice_clean_rx_irq(struct ice_rx_ring *rx_ring, int budget)
#endif
xdp_init_buff(&xdp, frame_sz, &rx_ring->xdp_rxq);

- xdp_prog = READ_ONCE(rx_ring->xdp_prog);
+ xdp_prog = rcu_dereference(rx_ring->xdp_info->prog_rcu);
if (xdp_prog)
xdp_ring = rx_ring->xdp_ring;

@@ -1489,6 +1488,8 @@ int ice_napi_poll(struct napi_struct *napi, int budget)
/* Max of 1 Rx ring in this q_vector so give it the budget */
budget_per_ring = budget;

+ rcu_read_lock();
+
ice_for_each_rx_ring(rx_ring, q_vector->rx) {
int cleaned;

@@ -1505,6 +1506,8 @@ int ice_napi_poll(struct napi_struct *napi, int budget)
clean_complete = false;
}

+ rcu_read_unlock();
+
/* If work not completed, return budget and polling will return */
if (!clean_complete) {
/* Set the writeback on ITR so partial completions of
diff --git a/drivers/net/ethernet/intel/ice/ice_txrx.h b/drivers/net/ethernet/intel/ice/ice_txrx.h
index ca902af54bb4..1fc31ab0bf33 100644
--- a/drivers/net/ethernet/intel/ice/ice_txrx.h
+++ b/drivers/net/ethernet/intel/ice/ice_txrx.h
@@ -290,7 +290,7 @@ struct ice_rx_ring {
struct rcu_head rcu; /* to avoid race on free */
/* CL4 - 3rd cacheline starts here */
struct ice_channel *ch;
- struct bpf_prog *xdp_prog;
+ const struct xdp_attachment_info *xdp_info;
struct ice_tx_ring *xdp_ring;
struct xsk_buff_pool *xsk_pool;
struct sk_buff *skb;
diff --git a/drivers/net/ethernet/intel/ice/ice_xsk.c b/drivers/net/ethernet/intel/ice/ice_xsk.c
index 49ba8bfdbf04..eb994cf68ff4 100644
--- a/drivers/net/ethernet/intel/ice/ice_xsk.c
+++ b/drivers/net/ethernet/intel/ice/ice_xsk.c
@@ -597,7 +597,7 @@ int ice_clean_rx_irq_zc(struct ice_rx_ring *rx_ring, int budget)
/* ZC patch is enabled only when XDP program is set,
* so here it can not be NULL
*/
- xdp_prog = READ_ONCE(rx_ring->xdp_prog);
+ xdp_prog = rcu_dereference(rx_ring->xdp_info->prog_rcu);
xdp_ring = rx_ring->xdp_ring;

while (likely(total_rx_packets < (unsigned int)budget)) {
--
2.36.1