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Message-ID: <CALs4sv0dPZWOZGC9HCMkFDR6hDGJ=SZSebhm5v6m-MKNOgA1JA@mail.gmail.com>
Date: Mon, 27 Oct 2025 19:28:33 +0530
From: Pavan Chebbi <pavan.chebbi@...adcom.com>
To: Dipayaan Roy <dipayanroy@...ux.microsoft.com>
Cc: kys@...rosoft.com, haiyangz@...rosoft.com, wei.liu@...nel.org,
decui@...rosoft.com, andrew+netdev@...n.ch, davem@...emloft.net,
edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com, longli@...rosoft.com,
kotaranov@...rosoft.com, horms@...nel.org, shradhagupta@...ux.microsoft.com,
ssengar@...ux.microsoft.com, ernis@...ux.microsoft.com,
shirazsaleem@...rosoft.com, linux-hyperv@...r.kernel.org,
netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-rdma@...r.kernel.org, dipayanroy@...rosoft.com
Subject: Re: [PATCH net-next] net: mana: Implement ndo_tx_timeout and
serialize queue resets per port.
On Mon, Oct 27, 2025 at 5:19 PM Dipayaan Roy
<dipayanroy@...ux.microsoft.com> wrote:
>
> Implement .ndo_tx_timeout for MANA so any stalled TX queue can be detected
> and a device-controlled port reset for all queues can be scheduled to an
> ordered workqueue. The reset for all queues on stall detection is
> recomended by hardware team.
>
> The change introduces a single ordered workqueue
> ("mana_per_port_queue_reset_wq") with WQ_UNBOUND | WQ_MEM_RECLAIM and
> queues exactly one work_struct per port onto it. This achieves:
>
> * Global FIFO across all port reset requests (alloc_ordered_workqueue).
> * Natural per-port de-duplication: the same work_struct cannot be
> queued twice while pending/running.
> * Avoids hogging a per-CPU kworker for long, may-sleep reset paths
> (WQ_UNBOUND).
> * Guarantees forward progress during memory pressure
> (WQ_MEM_RECLAIM rescuer).
>
> Signed-off-by: Dipayaan Roy <dipayanroy@...ux.microsoft.com>
> ---
> drivers/net/ethernet/microsoft/mana/mana_en.c | 83 +++++++++++++++++++
> include/net/mana/gdma.h | 6 +-
> include/net/mana/mana.h | 12 +++
> 3 files changed, 100 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/net/ethernet/microsoft/mana/mana_en.c b/drivers/net/ethernet/microsoft/mana/mana_en.c
> index f4fc86f20213..2833f66d8b2b 100644
> --- a/drivers/net/ethernet/microsoft/mana/mana_en.c
> +++ b/drivers/net/ethernet/microsoft/mana/mana_en.c
> @@ -258,6 +258,45 @@ static int mana_get_gso_hs(struct sk_buff *skb)
> return gso_hs;
> }
>
> +static void mana_per_port_queue_reset_work_handler(struct work_struct *work)
> +{
> + struct mana_queue_reset_work *reset_queue_work =
> + container_of(work, struct mana_queue_reset_work, work);
> + struct mana_port_context *apc = reset_queue_work->apc;
> + struct net_device *ndev = apc->ndev;
> + struct mana_context *ac = apc->ac;
> + int err;
> +
> + if (!rtnl_trylock()) {
> + /* Someone else holds RTNL, requeue and exit. */
> + queue_work(ac->per_port_queue_reset_wq,
> + &apc->queue_reset_work.work);
> + return;
> + }
> +
> + /* Pre-allocate buffers to prevent failure in mana_attach later */
> + err = mana_pre_alloc_rxbufs(apc, ndev->mtu, apc->num_queues);
> + if (err) {
> + netdev_err(ndev, "Insufficient memory for reset post tx stall detection\n");
> + goto out;
> + }
> +
> + err = mana_detach(ndev, false);
> + if (err) {
> + netdev_err(ndev, "mana_detach failed: %d\n", err);
> + goto dealloc_pre_rxbufs;
> + }
> +
> + err = mana_attach(ndev);
> + if (err)
> + netdev_err(ndev, "mana_attach failed: %d\n", err);
> +
> +dealloc_pre_rxbufs:
> + mana_pre_dealloc_rxbufs(apc);
> +out:
> + rtnl_unlock();
> +}
> +
> netdev_tx_t mana_start_xmit(struct sk_buff *skb, struct net_device *ndev)
> {
> enum mana_tx_pkt_format pkt_fmt = MANA_SHORT_PKT_FMT;
> @@ -762,6 +801,25 @@ static int mana_change_mtu(struct net_device *ndev, int new_mtu)
> return err;
> }
>
> +static void mana_tx_timeout(struct net_device *netdev, unsigned int txqueue)
> +{
> + struct mana_port_context *apc = netdev_priv(netdev);
> + struct mana_context *ac = apc->ac;
> + struct gdma_context *gc = ac->gdma_dev->gdma_context;
> +
> + netdev_warn(netdev, "%s(): called on txq: %u\n", __func__, txqueue);
> +
> + /* Already in service, hence tx queue reset is not required.*/
> + if (gc->in_service)
> + return;
> +
> + /* Note: If there are pending queue reset work for this port(apc),
> + * subsequent request queued up drom here are ignored. This is because
%s/drom/from/
> + * we are using the same work instance per port(apc).
> + */
> + queue_work(ac->per_port_queue_reset_wq, &apc->queue_reset_work.work);
> +}
> +
> static int mana_shaper_set(struct net_shaper_binding *binding,
> const struct net_shaper *shaper,
> struct netlink_ext_ack *extack)
> @@ -844,7 +902,9 @@ static const struct net_device_ops mana_devops = {
> .ndo_bpf = mana_bpf,
> .ndo_xdp_xmit = mana_xdp_xmit,
> .ndo_change_mtu = mana_change_mtu,
> + .ndo_tx_timeout = mana_tx_timeout,
> .net_shaper_ops = &mana_shaper_ops,
> +
> };
>
> static void mana_cleanup_port_context(struct mana_port_context *apc)
> @@ -3218,6 +3278,7 @@ static int mana_probe_port(struct mana_context *ac, int port_idx,
> ndev->min_mtu = ETH_MIN_MTU;
> ndev->needed_headroom = MANA_HEADROOM;
> ndev->dev_port = port_idx;
> + ndev->watchdog_timeo = MANA_TXQ_TIMEOUT;
> SET_NETDEV_DEV(ndev, gc->dev);
>
> netif_set_tso_max_size(ndev, GSO_MAX_SIZE);
> @@ -3255,6 +3316,11 @@ static int mana_probe_port(struct mana_context *ac, int port_idx,
>
> debugfs_create_u32("current_speed", 0400, apc->mana_port_debugfs, &apc->speed);
>
> + /* Initialize the per port queue reset work.*/
> + apc->queue_reset_work.apc = apc;
> + INIT_WORK(&apc->queue_reset_work.work,
> + mana_per_port_queue_reset_work_handler);
> +
> return 0;
>
> free_indir:
> @@ -3456,6 +3522,15 @@ int mana_probe(struct gdma_dev *gd, bool resuming)
> if (ac->num_ports > MAX_PORTS_IN_MANA_DEV)
> ac->num_ports = MAX_PORTS_IN_MANA_DEV;
>
> + ac->per_port_queue_reset_wq =
> + alloc_ordered_workqueue("mana_per_port_queue_reset_wq",
> + WQ_UNBOUND | WQ_MEM_RECLAIM);
> + if (!ac->per_port_queue_reset_wq) {
> + dev_err(dev, "Failed to allocate per port queue reset workqueue\n");
> + err = -ENOMEM;
> + goto out;
> + }
> +
> if (!resuming) {
> for (i = 0; i < ac->num_ports; i++) {
> err = mana_probe_port(ac, i, &ac->ports[i]);
> @@ -3528,6 +3603,8 @@ void mana_remove(struct gdma_dev *gd, bool suspending)
> */
> rtnl_lock();
>
> + cancel_work_sync(&apc->queue_reset_work.work);
> +
> err = mana_detach(ndev, false);
> if (err)
> netdev_err(ndev, "Failed to detach vPort %d: %d\n",
> @@ -3547,6 +3624,12 @@ void mana_remove(struct gdma_dev *gd, bool suspending)
> free_netdev(ndev);
> }
>
> + if (ac->per_port_queue_reset_wq) {
> + drain_workqueue(ac->per_port_queue_reset_wq);
> + destroy_workqueue(ac->per_port_queue_reset_wq);
destroy will take care of the drain.
> + ac->per_port_queue_reset_wq = NULL;
> + }
> +
> mana_destroy_eq(ac);
> out:
> mana_gd_deregister_device(gd);
> diff --git a/include/net/mana/gdma.h b/include/net/mana/gdma.h
> index 57df78cfbf82..1f8c536ba3be 100644
> --- a/include/net/mana/gdma.h
> +++ b/include/net/mana/gdma.h
> @@ -591,6 +591,9 @@ enum {
> /* Driver can self reset on FPGA Reconfig EQE notification */
> #define GDMA_DRV_CAP_FLAG_1_HANDLE_RECONFIG_EQE BIT(17)
>
> +/* Driver detects stalled send queues and recovers them */
> +#define GDMA_DRV_CAP_FLAG_1_HANDLE_STALL_SQ_RECOVERY BIT(18)
> +
> #define GDMA_DRV_CAP_FLAGS1 \
> (GDMA_DRV_CAP_FLAG_1_EQ_SHARING_MULTI_VPORT | \
> GDMA_DRV_CAP_FLAG_1_NAPI_WKDONE_FIX | \
> @@ -599,7 +602,8 @@ enum {
> GDMA_DRV_CAP_FLAG_1_DEV_LIST_HOLES_SUP | \
> GDMA_DRV_CAP_FLAG_1_DYNAMIC_IRQ_ALLOC_SUPPORT | \
> GDMA_DRV_CAP_FLAG_1_SELF_RESET_ON_EQE | \
> - GDMA_DRV_CAP_FLAG_1_HANDLE_RECONFIG_EQE)
> + GDMA_DRV_CAP_FLAG_1_HANDLE_RECONFIG_EQE | \
> + GDMA_DRV_CAP_FLAG_1_HANDLE_STALL_SQ_RECOVERY)
>
> #define GDMA_DRV_CAP_FLAGS2 0
>
> diff --git a/include/net/mana/mana.h b/include/net/mana/mana.h
> index 0921485565c0..9b8f236f27c9 100644
> --- a/include/net/mana/mana.h
> +++ b/include/net/mana/mana.h
> @@ -67,6 +67,11 @@ enum TRI_STATE {
>
> #define MANA_RX_FRAG_ALIGNMENT 64
>
> +/* Timeout value for Txq stall detetcion & recovery used by ndo_tx_timeout.
%s/detetcion/detection/
> + * The value is chosen after considering fpga re-config scenarios.
> + */
> +#define MANA_TXQ_TIMEOUT (15 * HZ)
> +
> struct mana_stats_rx {
> u64 packets;
> u64 bytes;
> @@ -475,13 +480,20 @@ struct mana_context {
>
> struct mana_eq *eqs;
> struct dentry *mana_eqs_debugfs;
> + struct workqueue_struct *per_port_queue_reset_wq;
>
> struct net_device *ports[MAX_PORTS_IN_MANA_DEV];
> };
>
> +struct mana_queue_reset_work {
> + struct work_struct work; // Work structure
> + struct mana_port_context *apc; // Pointer to the port context
Block comment style is preferred instead of //
> +};
> +
> struct mana_port_context {
> struct mana_context *ac;
> struct net_device *ndev;
> + struct mana_queue_reset_work queue_reset_work;
>
> u8 mac_addr[ETH_ALEN];
>
> --
> 2.43.0
>
>
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