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ionic: Allow XDP program to be hot swapped
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Using examples of other driver(s), add the ability to hot-swap an XDP
program without having to reconfigure the queues. To prevent the
q->xdp_prog to be read/written more than once use READ_ONCE() and
WRITE_ONCE() on the q->xdp_prog.

The q->xdp_prog was being checked in multiple different for loops in the
hot path. The change to allow xdp_prog hot swapping created the
possibility for many READ_ONCE(q->xdp_prog) calls during a single napi
callback. Refactor the Rx napi handling to allow a previous
READ_ONCE(q->xdp_prog) (or NULL for hwstamp_rxq) to be passed into the
relevant functions.

Also, move other Rx related hotpath handling into the newly created
ionic_rx_cq_service() function to reduce the scope of the xdp_prog
local variable and put all Rx handling in one function similar to Tx.

Signed-off-by: Brett Creeley <[email protected]>
Signed-off-by: Shannon Nelson <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>
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@brettcreeley @kuba-moo
brettcreeley authored and kuba-moo committed Sep 10, 2024
1 parent ac8813c commit 3c0bf13
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Showing 3 changed files with 52 additions and 22 deletions.
12 changes: 8 additions & 4 deletions drivers/net/ethernet/pensando/ionic/ionic_lif.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1074,7 +1074,7 @@ int ionic_lif_create_hwstamp_rxq(struct ionic_lif *lif)
goto err_qcq_init;

if (test_bit(IONIC_LIF_F_UP, lif->state)) {
ionic_rx_fill(&rxq->q);
ionic_rx_fill(&rxq->q, NULL);
err = ionic_qcq_enable(rxq);
if (err)
goto err_qcq_enable;
Expand Down Expand Up @@ -2190,7 +2190,8 @@ static int ionic_txrx_enable(struct ionic_lif *lif)
goto err_out;
}

ionic_rx_fill(&lif->rxqcqs[i]->q);
ionic_rx_fill(&lif->rxqcqs[i]->q,
READ_ONCE(lif->rxqcqs[i]->q.xdp_prog));
err = ionic_qcq_enable(lif->rxqcqs[i]);
if (err)
goto err_out;
Expand All @@ -2203,7 +2204,7 @@ static int ionic_txrx_enable(struct ionic_lif *lif)
}

if (lif->hwstamp_rxq) {
ionic_rx_fill(&lif->hwstamp_rxq->q);
ionic_rx_fill(&lif->hwstamp_rxq->q, NULL);
err = ionic_qcq_enable(lif->hwstamp_rxq);
if (err)
goto err_out_hwstamp_rx;
Expand Down Expand Up @@ -2746,7 +2747,7 @@ static void ionic_xdp_rxqs_prog_update(struct ionic_lif *lif)
for (i = 0; i < lif->ionic->nrxqs_per_lif && lif->rxqcqs[i]; i++) {
struct ionic_queue *q = &lif->rxqcqs[i]->q;

q->xdp_prog = xdp_prog;
WRITE_ONCE(q->xdp_prog, xdp_prog);
}
}

Expand Down Expand Up @@ -2777,6 +2778,9 @@ static int ionic_xdp_config(struct net_device *netdev, struct netdev_bpf *bpf)

if (!netif_running(netdev)) {
old_prog = xchg(&lif->xdp_prog, bpf->prog);
} else if (lif->xdp_prog && bpf->prog) {
old_prog = xchg(&lif->xdp_prog, bpf->prog);
ionic_xdp_rxqs_prog_update(lif);
} else {
struct ionic_queue_params qparams;

Expand Down
58 changes: 41 additions & 17 deletions drivers/net/ethernet/pensando/ionic/ionic_txrx.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -602,7 +602,8 @@ static bool ionic_run_xdp(struct ionic_rx_stats *stats,

static void ionic_rx_clean(struct ionic_queue *q,
struct ionic_rx_desc_info *desc_info,
struct ionic_rxq_comp *comp)
struct ionic_rxq_comp *comp,
struct bpf_prog *xdp_prog)
{
struct net_device *netdev = q->lif->netdev;
struct ionic_qcq *qcq = q_to_qcq(q);
Expand Down Expand Up @@ -631,8 +632,8 @@ static void ionic_rx_clean(struct ionic_queue *q,
stats->pkts++;
stats->bytes += len;

if (q->xdp_prog) {
if (ionic_run_xdp(stats, netdev, q->xdp_prog, q, desc_info->bufs, len))
if (xdp_prog) {
if (ionic_run_xdp(stats, netdev, xdp_prog, q, desc_info->bufs, len))
return;
synced = true;
headroom = XDP_PACKET_HEADROOM;
Expand Down Expand Up @@ -718,7 +719,7 @@ static void ionic_rx_clean(struct ionic_queue *q,
napi_gro_frags(&qcq->napi);
}

bool ionic_rx_service(struct ionic_cq *cq)
static bool __ionic_rx_service(struct ionic_cq *cq, struct bpf_prog *xdp_prog)
{
struct ionic_rx_desc_info *desc_info;
struct ionic_queue *q = cq->bound_q;
Expand All @@ -740,11 +741,16 @@ bool ionic_rx_service(struct ionic_cq *cq)
q->tail_idx = (q->tail_idx + 1) & (q->num_descs - 1);

/* clean the related q entry, only one per qc completion */
ionic_rx_clean(q, desc_info, comp);
ionic_rx_clean(q, desc_info, comp, xdp_prog);

return true;
}

bool ionic_rx_service(struct ionic_cq *cq)
{
return __ionic_rx_service(cq, NULL);
}

static inline void ionic_write_cmb_desc(struct ionic_queue *q,
void *desc)
{
Expand All @@ -755,7 +761,7 @@ static inline void ionic_write_cmb_desc(struct ionic_queue *q,
memcpy_toio(&q->cmb_txq[q->head_idx], desc, sizeof(q->cmb_txq[0]));
}

void ionic_rx_fill(struct ionic_queue *q)
void ionic_rx_fill(struct ionic_queue *q, struct bpf_prog *xdp_prog)
{
struct net_device *netdev = q->lif->netdev;
struct ionic_rx_desc_info *desc_info;
Expand Down Expand Up @@ -783,7 +789,7 @@ void ionic_rx_fill(struct ionic_queue *q)

len = netdev->mtu + VLAN_ETH_HLEN;

if (q->xdp_prog) {
if (xdp_prog) {
/* Always alloc the full size buffer, but only need
* the actual frag_len in the descriptor
* XDP uses space in the first buffer, so account for
Expand Down Expand Up @@ -964,6 +970,32 @@ static void ionic_xdp_do_flush(struct ionic_cq *cq)
}
}

static unsigned int ionic_rx_cq_service(struct ionic_cq *cq,
unsigned int work_to_do)
{
struct ionic_queue *q = cq->bound_q;
unsigned int work_done = 0;
struct bpf_prog *xdp_prog;

if (work_to_do == 0)
return 0;

xdp_prog = READ_ONCE(q->xdp_prog);
while (__ionic_rx_service(cq, xdp_prog)) {
if (cq->tail_idx == cq->num_descs - 1)
cq->done_color = !cq->done_color;

cq->tail_idx = (cq->tail_idx + 1) & (cq->num_descs - 1);

if (++work_done >= work_to_do)
break;
}
ionic_rx_fill(q, xdp_prog);
ionic_xdp_do_flush(cq);

return work_done;
}

int ionic_rx_napi(struct napi_struct *napi, int budget)
{
struct ionic_qcq *qcq = napi_to_qcq(napi);
Expand All @@ -974,12 +1006,8 @@ int ionic_rx_napi(struct napi_struct *napi, int budget)
if (unlikely(!budget))
return budget;

work_done = ionic_cq_service(cq, budget,
ionic_rx_service, NULL, NULL);
work_done = ionic_rx_cq_service(cq, budget);

ionic_rx_fill(cq->bound_q);

ionic_xdp_do_flush(cq);
if (work_done < budget && napi_complete_done(napi, work_done)) {
ionic_dim_update(qcq, IONIC_LIF_F_RX_DIM_INTR);
flags |= IONIC_INTR_CRED_UNMASK;
Expand Down Expand Up @@ -1020,12 +1048,8 @@ int ionic_txrx_napi(struct napi_struct *napi, int budget)
if (unlikely(!budget))
return budget;

rx_work_done = ionic_cq_service(rxcq, budget,
ionic_rx_service, NULL, NULL);

ionic_rx_fill(rxcq->bound_q);
rx_work_done = ionic_rx_cq_service(rxcq, budget);

ionic_xdp_do_flush(rxcq);
if (rx_work_done < budget && napi_complete_done(napi, rx_work_done)) {
ionic_dim_update(rxqcq, 0);
flags |= IONIC_INTR_CRED_UNMASK;
Expand Down
4 changes: 3 additions & 1 deletion drivers/net/ethernet/pensando/ionic/ionic_txrx.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -4,9 +4,11 @@
#ifndef _IONIC_TXRX_H_
#define _IONIC_TXRX_H_

struct bpf_prog;

void ionic_tx_flush(struct ionic_cq *cq);

void ionic_rx_fill(struct ionic_queue *q);
void ionic_rx_fill(struct ionic_queue *q, struct bpf_prog *xdp_prog);
void ionic_rx_empty(struct ionic_queue *q);
void ionic_tx_empty(struct ionic_queue *q);
int ionic_rx_napi(struct napi_struct *napi, int budget);
Expand Down

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