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Date: Thu, 27 Jul 2023 14:04:55 -0400
From: Andy Gospodarek <andrew.gospodarek@...adcom.com>
To: Jakub Kicinski <kuba@...nel.org>
Cc: davem@...emloft.net, netdev@...r.kernel.org, edumazet@...gle.com,
pabeni@...hat.com, michael.chan@...adcom.com
Subject: Re: [PATCH net] bnxt: don't handle XDP in netpoll
On Thu, Jul 27, 2023 at 10:05:05AM -0700, Jakub Kicinski wrote:
> Similarly to other recently fixed drivers make sure we don't
> try to access XDP or page pool APIs when NAPI budget is 0.
> NAPI budget of 0 may mean that we are in netpoll.
>
> This may result in running software IRQs in hard IRQ context,
> leading to deadlocks or crashes.
>
> Fixes: 322b87ca55f2 ("bnxt_en: add page_pool support")
> Signed-off-by: Jakub Kicinski <kuba@...nel.org>
Reviewed-by: Andy Gospodarek <gospo@...adcom.com>
> ---
> CC: michael.chan@...adcom.com
> CC: gospo@...adcom.com
>
> Side note - having to plumb the "budget" everywhere really makes
> me wonder if we shouldn't have had those APIs accept a pointer
> to napi_struct instead :S
We could also consider adding budget to struct bnxt_napi. I'm not sure that
would work in all cases, however.
I'm good if this goes in as-is and we make enhancements from this as a starting
point.
> ---
> drivers/net/ethernet/broadcom/bnxt/bnxt.c | 19 +++++++++++--------
> drivers/net/ethernet/broadcom/bnxt/bnxt.h | 2 +-
> drivers/net/ethernet/broadcom/bnxt/bnxt_xdp.c | 6 +++++-
> drivers/net/ethernet/broadcom/bnxt/bnxt_xdp.h | 3 ++-
> 4 files changed, 19 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt.c b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
> index a3bbd13c070f..fe1d645c39d0 100644
> --- a/drivers/net/ethernet/broadcom/bnxt/bnxt.c
> +++ b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
> @@ -687,7 +687,8 @@ static netdev_tx_t bnxt_start_xmit(struct sk_buff *skb, struct net_device *dev)
> return NETDEV_TX_OK;
> }
>
> -static void bnxt_tx_int(struct bnxt *bp, struct bnxt_napi *bnapi, int nr_pkts)
> +static void bnxt_tx_int(struct bnxt *bp, struct bnxt_napi *bnapi, int nr_pkts,
> + int budget)
> {
> struct bnxt_tx_ring_info *txr = bnapi->tx_ring;
> struct netdev_queue *txq = netdev_get_tx_queue(bp->dev, txr->txq_index);
> @@ -2595,10 +2596,11 @@ static int __bnxt_poll_work(struct bnxt *bp, struct bnxt_cp_ring_info *cpr,
> return rx_pkts;
> }
>
> -static void __bnxt_poll_work_done(struct bnxt *bp, struct bnxt_napi *bnapi)
> +static void __bnxt_poll_work_done(struct bnxt *bp, struct bnxt_napi *bnapi,
> + int budget)
> {
> if (bnapi->tx_pkts && !bnapi->tx_fault) {
> - bnapi->tx_int(bp, bnapi, bnapi->tx_pkts);
> + bnapi->tx_int(bp, bnapi, bnapi->tx_pkts, budget);
> bnapi->tx_pkts = 0;
> }
>
> @@ -2629,7 +2631,7 @@ static int bnxt_poll_work(struct bnxt *bp, struct bnxt_cp_ring_info *cpr,
> */
> bnxt_db_cq(bp, &cpr->cp_db, cpr->cp_raw_cons);
>
> - __bnxt_poll_work_done(bp, bnapi);
> + __bnxt_poll_work_done(bp, bnapi, budget);
> return rx_pkts;
> }
>
> @@ -2760,7 +2762,7 @@ static int __bnxt_poll_cqs(struct bnxt *bp, struct bnxt_napi *bnapi, int budget)
> }
>
> static void __bnxt_poll_cqs_done(struct bnxt *bp, struct bnxt_napi *bnapi,
> - u64 dbr_type)
> + u64 dbr_type, int budget)
> {
> struct bnxt_cp_ring_info *cpr = &bnapi->cp_ring;
> int i;
> @@ -2776,7 +2778,7 @@ static void __bnxt_poll_cqs_done(struct bnxt *bp, struct bnxt_napi *bnapi,
> cpr2->had_work_done = 0;
> }
> }
> - __bnxt_poll_work_done(bp, bnapi);
> + __bnxt_poll_work_done(bp, bnapi, budget);
> }
>
> static int bnxt_poll_p5(struct napi_struct *napi, int budget)
> @@ -2806,7 +2808,8 @@ static int bnxt_poll_p5(struct napi_struct *napi, int budget)
> if (cpr->has_more_work)
> break;
>
> - __bnxt_poll_cqs_done(bp, bnapi, DBR_TYPE_CQ_ARMALL);
> + __bnxt_poll_cqs_done(bp, bnapi, DBR_TYPE_CQ_ARMALL,
> + budget);
> cpr->cp_raw_cons = raw_cons;
> if (napi_complete_done(napi, work_done))
> BNXT_DB_NQ_ARM_P5(&cpr->cp_db,
> @@ -2836,7 +2839,7 @@ static int bnxt_poll_p5(struct napi_struct *napi, int budget)
> }
> raw_cons = NEXT_RAW_CMP(raw_cons);
> }
> - __bnxt_poll_cqs_done(bp, bnapi, DBR_TYPE_CQ);
> + __bnxt_poll_cqs_done(bp, bnapi, DBR_TYPE_CQ, budget);
> if (raw_cons != cpr->cp_raw_cons) {
> cpr->cp_raw_cons = raw_cons;
> BNXT_DB_NQ_P5(&cpr->cp_db, raw_cons);
> diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt.h b/drivers/net/ethernet/broadcom/bnxt/bnxt.h
> index 9d16757e27fe..bd44a5701e5f 100644
> --- a/drivers/net/ethernet/broadcom/bnxt/bnxt.h
> +++ b/drivers/net/ethernet/broadcom/bnxt/bnxt.h
> @@ -1005,7 +1005,7 @@ struct bnxt_napi {
> struct bnxt_tx_ring_info *tx_ring;
>
> void (*tx_int)(struct bnxt *, struct bnxt_napi *,
> - int);
> + int tx_pkts, int budget);
> int tx_pkts;
> u8 events;
> u8 tx_fault:1;
> diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt_xdp.c b/drivers/net/ethernet/broadcom/bnxt/bnxt_xdp.c
> index 5b6fbdc4dc40..33b7eddfbf41 100644
> --- a/drivers/net/ethernet/broadcom/bnxt/bnxt_xdp.c
> +++ b/drivers/net/ethernet/broadcom/bnxt/bnxt_xdp.c
> @@ -125,7 +125,8 @@ static void __bnxt_xmit_xdp_redirect(struct bnxt *bp,
> dma_unmap_len_set(tx_buf, len, 0);
> }
>
> -void bnxt_tx_int_xdp(struct bnxt *bp, struct bnxt_napi *bnapi, int nr_pkts)
> +void bnxt_tx_int_xdp(struct bnxt *bp, struct bnxt_napi *bnapi, int nr_pkts,
> + int budget)
> {
> struct bnxt_tx_ring_info *txr = bnapi->tx_ring;
> struct bnxt_rx_ring_info *rxr = bnapi->rx_ring;
> @@ -135,6 +136,9 @@ void bnxt_tx_int_xdp(struct bnxt *bp, struct bnxt_napi *bnapi, int nr_pkts)
> u16 last_tx_cons = tx_cons;
> int i, j, frags;
>
> + if (!budget)
> + return;
> +
> for (i = 0; i < nr_pkts; i++) {
> tx_buf = &txr->tx_buf_ring[tx_cons];
>
> diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt_xdp.h b/drivers/net/ethernet/broadcom/bnxt/bnxt_xdp.h
> index ea430d6961df..3ab47ae2f26d 100644
> --- a/drivers/net/ethernet/broadcom/bnxt/bnxt_xdp.h
> +++ b/drivers/net/ethernet/broadcom/bnxt/bnxt_xdp.h
> @@ -16,7 +16,8 @@ struct bnxt_sw_tx_bd *bnxt_xmit_bd(struct bnxt *bp,
> struct bnxt_tx_ring_info *txr,
> dma_addr_t mapping, u32 len,
> struct xdp_buff *xdp);
> -void bnxt_tx_int_xdp(struct bnxt *bp, struct bnxt_napi *bnapi, int nr_pkts);
> +void bnxt_tx_int_xdp(struct bnxt *bp, struct bnxt_napi *bnapi, int nr_pkts,
> + int budget);
> bool bnxt_rx_xdp(struct bnxt *bp, struct bnxt_rx_ring_info *rxr, u16 cons,
> struct xdp_buff xdp, struct page *page, u8 **data_ptr,
> unsigned int *len, u8 *event);
> --
> 2.41.0
>
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