net: mana: add ethtool private flag for full-page RX buffers

drivers/net/ethernet/microsoft/mana/mana_ethtool.c +0 -0

index a28ca461c135..dfd222de11d0 100644

drivers/net/ethernet/microsoft/mana/mana_ethtool.c +0 -0

@@ -590,6 +609,88 @@ static int mana_get_link_ksettings(struct net_device *ndev,
 	return 0;
 }
 

drivers/net/ethernet/microsoft/mana/mana_ethtool.c +64 -0

+static int mana_set_priv_flags(struct net_device *ndev, u32 priv_flags)
+{
+	struct mana_port_context *apc = netdev_priv(ndev);
+	u32 changed = apc->priv_flags ^ priv_flags;
+	u32 old_priv_flags = apc->priv_flags;
+	bool schedule_port_reset = false;
+	int err = 0;
+
+	if (!changed)
+		return 0;
+
+	/* Reject unknown bits */
+	if (priv_flags & ~GENMASK(MANA_PRIV_FLAG_MAX - 1, 0))
+		return -EINVAL;
+
+	if (changed & BIT(MANA_PRIV_FLAG_USE_FULL_PAGE_RXBUF)) {
+		apc->priv_flags = priv_flags;
+
+		if (!apc->port_is_up) {
+			/* Port is down, flag updated to apply on next up
+			 * so just return.
+			 */
+			return 0;
+		}
+
+		/* 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 new allocations\n");
+			apc->priv_flags = old_priv_flags;
+			return err;
+		}
+
+		err = mana_detach(ndev, false);
+		if (err) {
+			netdev_err(ndev, "mana_detach failed: %d\n", err);
+			apc->priv_flags = old_priv_flags;
+
+			/* Port is in an inconsistent state. Restore
+			 * 'port_is_up' so that queue reset work handler
+			 * can properly detach and re-attach.
+			 */
+			apc->port_is_up = true;
+			schedule_port_reset = true;
+			goto out;
+		}
+
+		err = mana_attach(ndev);
+		if (err) {
+			netdev_err(ndev, "mana_attach failed: %d\n", err);
+			apc->priv_flags = old_priv_flags;
+
+			/* Restore 'port_is_up' so the reset work handler
+			 * can properly detach/attach. Without this,
+			 * the handler sees port_is_up=false and skips
+			 * queue allocation, leaving the port dead.
+			 */
+			apc->port_is_up = true;
+			schedule_port_reset = true;
+		}
+	}

This is an AI-generated review of your patch. The human sending this email has considered the AI review valid, or at least plausible.
---
net: mana: force full-page RX buffers via ethtool private flag

This patch adds an ethtool private flag "full-page-rx" that forces one RX buffer per page, bypassing the page_pool fragment path, to address a 15-20% throughput regression seen on some 4K PAGE_SIZE ARM64 platforms under high connection counts. Toggling the flag triggers mana_detach() + mana_attach() to apply the new RX buffer layout.

Quoted 4 lines

drivers/net/ethernet/microsoft/mana/mana_ethtool.c +0 -0

index a28ca461c135..dfd222de11d0 100644

[ ... ]

Quoted 4 lines

drivers/net/ethernet/microsoft/mana/mana_ethtool.c +0 -0

@@ -590,6 +609,88 @@ static int mana_get_link_ksettings(struct net_device *ndev,
 	return 0;
 }
 

[ ... ]

Quoted 64 lines

drivers/net/ethernet/microsoft/mana/mana_ethtool.c +64 -0

+static int mana_set_priv_flags(struct net_device *ndev, u32 priv_flags)
+{
+	struct mana_port_context *apc = netdev_priv(ndev);
+	u32 changed = apc->priv_flags ^ priv_flags;
+	u32 old_priv_flags = apc->priv_flags;
+	bool schedule_port_reset = false;
+	int err = 0;
+
+	if (!changed)
+		return 0;
+
+	/* Reject unknown bits */
+	if (priv_flags & ~GENMASK(MANA_PRIV_FLAG_MAX - 1, 0))
+		return -EINVAL;
+
+	if (changed & BIT(MANA_PRIV_FLAG_USE_FULL_PAGE_RXBUF)) {
+		apc->priv_flags = priv_flags;
+
+		if (!apc->port_is_up) {
+			/* Port is down, flag updated to apply on next up
+			 * so just return.
+			 */
+			return 0;
+		}
+
+		/* 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 new allocations\n");
+			apc->priv_flags = old_priv_flags;
+			return err;
+		}
+
+		err = mana_detach(ndev, false);
+		if (err) {
+			netdev_err(ndev, "mana_detach failed: %d\n", err);
+			apc->priv_flags = old_priv_flags;
+
+			/* Port is in an inconsistent state. Restore
+			 * 'port_is_up' so that queue reset work handler
+			 * can properly detach and re-attach.
+			 */
+			apc->port_is_up = true;
+			schedule_port_reset = true;
+			goto out;
+		}
+
+		err = mana_attach(ndev);
+		if (err) {
+			netdev_err(ndev, "mana_attach failed: %d\n", err);
+			apc->priv_flags = old_priv_flags;
+
+			/* Restore 'port_is_up' so the reset work handler
+			 * can properly detach/attach. Without this,
+			 * the handler sees port_is_up=false and skips
+			 * queue allocation, leaving the port dead.
+			 */
+			apc->port_is_up = true;
+			schedule_port_reset = true;
+		}
+	}

drivers/net/ethernet/microsoft/mana/mana_ethtool.c static int mana_get_link_ksettings(struct net_device *ndev, · line 692

Quoted 10 lines

drivers/net/ethernet/microsoft/mana/mana_ethtool.c +10 -0

+
+out:
+	mana_pre_dealloc_rxbufs(apc);
+
+	if (schedule_port_reset)
+		queue_work(apc->ac->per_port_queue_reset_wq,
+			   &apc->queue_reset_work);
+
+	return err;
+}

[High]
Can this failure path oops inside the reset work handler?

When mana_attach() fails after mana_detach() has already torn the vport down, apc->tx_qp has been set to NULL by mana_destroy_txq() and apc->rxqs has been cleared by mana_cleanup_port_context(). This code then forces apc->port_is_up back to true and queues apc->queue_reset_work:

    apc->port_is_up = true;
    schedule_port_reset = true;

When mana_per_port_queue_reset_work_handler runs it calls mana_detach(ndev, false), which latches port_st_save = port_is_up = true and, because port_st_save is true, invokes mana_dealloc_queues(). The TX drain loop there does:

    txq = &apc->tx_qp[i].txq;
    atomic_read(&txq->pending_sends);

with no NULL check on apc->tx_qp, and mana_destroy_vport further down iterates apc->rxqs[rxq_idx] while rxqs is NULL. Would that produce a NULL pointer dereference in the workqueue worker whenever mana_attach() fails here (for example on an allocation failure in mana_init_port_context or mana_create_txq, or a transient HW command failure in mana_query_vport_cfg / mana_cfg_vport)?

The mana_detach() failure path above (goto out) reaches mana_dealloc_queues() through the same chain and looks to have the same exposure.

For comparison, mana_change_mtu() handles a mana_attach() failure by returning the error without scheduling a reset. Would a similar treatment here avoid the asynchronous oops, or is there a reason the reset must be scheduled in this specific failure case?

Signature · 1 line

pw-bot: cr

Quoted 126 lines · Jakub Kicinski

This is an AI-generated review of your patch. The human sending this email has considered the AI review valid, or at least plausible.
---
net: mana: force full-page RX buffers via ethtool private flag

This patch adds an ethtool private flag "full-page-rx" that forces one RX buffer per page, bypassing the page_pool fragment path, to address a 15-20% throughput regression seen on some 4K PAGE_SIZE ARM64 platforms under high connection counts. Toggling the flag triggers mana_detach() + mana_attach() to apply the new RX buffer layout.

Quoted 4 lines

drivers/net/ethernet/microsoft/mana/mana_ethtool.c +0 -0

index a28ca461c135..dfd222de11d0 100644

[ ... ]

Quoted 4 lines

drivers/net/ethernet/microsoft/mana/mana_ethtool.c +0 -0

@@ -590,6 +609,88 @@ static int mana_get_link_ksettings(struct net_device *ndev,
 	return 0;
 }
 

[ ... ]

Quoted 64 lines

drivers/net/ethernet/microsoft/mana/mana_ethtool.c +64 -0

+static int mana_set_priv_flags(struct net_device *ndev, u32 priv_flags)
+{
+	struct mana_port_context *apc = netdev_priv(ndev);
+	u32 changed = apc->priv_flags ^ priv_flags;
+	u32 old_priv_flags = apc->priv_flags;
+	bool schedule_port_reset = false;
+	int err = 0;
+
+	if (!changed)
+		return 0;
+
+	/* Reject unknown bits */
+	if (priv_flags & ~GENMASK(MANA_PRIV_FLAG_MAX - 1, 0))
+		return -EINVAL;
+
+	if (changed & BIT(MANA_PRIV_FLAG_USE_FULL_PAGE_RXBUF)) {
+		apc->priv_flags = priv_flags;
+
+		if (!apc->port_is_up) {
+			/* Port is down, flag updated to apply on next up
+			 * so just return.
+			 */
+			return 0;
+		}
+
+		/* 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 new allocations\n");
+			apc->priv_flags = old_priv_flags;
+			return err;
+		}
+
+		err = mana_detach(ndev, false);
+		if (err) {
+			netdev_err(ndev, "mana_detach failed: %d\n", err);
+			apc->priv_flags = old_priv_flags;
+
+			/* Port is in an inconsistent state. Restore
+			 * 'port_is_up' so that queue reset work handler
+			 * can properly detach and re-attach.
+			 */
+			apc->port_is_up = true;
+			schedule_port_reset = true;
+			goto out;
+		}
+
+		err = mana_attach(ndev);
+		if (err) {
+			netdev_err(ndev, "mana_attach failed: %d\n", err);
+			apc->priv_flags = old_priv_flags;
+
+			/* Restore 'port_is_up' so the reset work handler
+			 * can properly detach/attach. Without this,
+			 * the handler sees port_is_up=false and skips
+			 * queue allocation, leaving the port dead.
+			 */
+			apc->port_is_up = true;
+			schedule_port_reset = true;
+		}
+	}

drivers/net/ethernet/microsoft/mana/mana_ethtool.c static int mana_get_link_ksettings(struct net_device *ndev, · line 692

Quoted 10 lines

drivers/net/ethernet/microsoft/mana/mana_ethtool.c +10 -0

+
+out:
+	mana_pre_dealloc_rxbufs(apc);
+
+	if (schedule_port_reset)
+		queue_work(apc->ac->per_port_queue_reset_wq,
+			   &apc->queue_reset_work);
+
+	return err;
+}

[High]
Can this failure path oops inside the reset work handler?

When mana_attach() fails after mana_detach() has already torn the vport down, apc->tx_qp has been set to NULL by mana_destroy_txq() and apc->rxqs has been cleared by mana_cleanup_port_context(). This code then forces apc->port_is_up back to true and queues apc->queue_reset_work:

    apc->port_is_up = true;
    schedule_port_reset = true;

When mana_per_port_queue_reset_work_handler runs it calls mana_detach(ndev, false), which latches port_st_save = port_is_up = true and, because port_st_save is true, invokes mana_dealloc_queues(). The TX drain loop there does:

    txq = &apc->tx_qp[i].txq;
    atomic_read(&txq->pending_sends);

with no NULL check on apc->tx_qp, and mana_destroy_vport further down iterates apc->rxqs[rxq_idx] while rxqs is NULL. Would that produce a NULL pointer dereference in the workqueue worker whenever mana_attach() fails here (for example on an allocation failure in mana_init_port_context or mana_create_txq, or a transient HW command failure in mana_query_vport_cfg / mana_cfg_vport)?

Quoted 3 lines

The mana_detach() failure path above (goto out) reaches mana_dealloc_queues() through the same chain and looks to have the same exposure.

Hi Jakub,

Thanks for your comments, I have sent a separate fixes series to the net tree that fixes the possible NULL pointer derefernce issue and also makes the reset handler safe for the case where it runs after a failed attach:
https://lore.kernel.org/all/[email protected]/

Quoted 7 lines

For comparison, mana_change_mtu() handles a mana_attach() failure by returning the error without scheduling a reset. Would a similar treatment here avoid the asynchronous oops, or is there a reason the reset must be scheduled in this specific failure case?

Signature · 1 line

pw-bot: cr

The full-page-rx private flag is intended to be driven by a udev rule that fires automatically during VM provisioning on affected platforms. If there is a transient failure, the VM fails to provision, requiring manual intervention.The reset handler retries the attach, giving the port a chance to recover to default config autonomously without intervention.

Regards
Dipayaan Roy

As the pre-requisite fixes patches are accepted now:
https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net.git/commit/?id=17bfe0a8c014
https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net.git/commit/?id=5b05aa36ee24

Can this series be merged now? Let me know if it needs a rebase or anything else.

Quoted 4 lines · On Thu, 28 May 2026 19:55:23 -0700 Dipayaan Roy wrote:

As the pre-requisite fixes patches are accepted now:
https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net.git/commit/?id=17bfe0a8c014
https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net.git/commit/?id=5b05aa36ee24

Quoted 2 lines

Can this series be merged now? Let me know if it needs a rebase or anything else.

If there's any dependency, functional or otherwise on the fixes you need to wait until they make their way to net-next.

Otherwise you can rebase and repost now.