[PATCH net-next v4 1/8] net: convert netmem_tx flag to enum

[Bobby Eshleman <bobbyeshleman@gmail.com>]

From: Bobby Eshleman <bobbyeshleman@meta.com>

Devices that support netmem TX previously set dev->netmem_tx = true.
This was checked in validate_xmit_unreadable_skb() to drop unreadable
skbs (skbs with dmabuf-backed frags) before they reach drivers that
would mishandle them or devices that would not have the iommu mappings
for them.

A subsequent patch will introduce a third state for virtual devices
that forward unreadable skbs without ever performing DMA on them. To
prepare for that, convert the boolean dev->netmem_tx into an enum:

NETMEM_TX_NONE   - no netmem TX support (drop unreadable skbs)
NETMEM_TX_DMA    - full support, device does DMA

Update the existing NIC drivers (bnxt, gve, mlx5, fbnic) and the
validators in net/core to use the new enum. No functional change.

Acked-by: Harshitha Ramamurthy <hramamurthy@google.com>
Acked-by: Stanislav Fomichev <sdf@fomichev.me>
Signed-off-by: Bobby Eshleman <bobbyeshleman@meta.com>
---
Changes in v4:
- netdevice.h: netmem_tx enum list -> only "device netmem TX mode" in
  comment (Stan)

Changes in v3:
- Split NO_DMA changes into subsequent commit (Jakub)
- Move !netdev->netmem_tx -> netdev->netmem_tx ==
  NETMEM_TX_NONE conversions to this patch (Jakub)

Changes in v2:
- Squash driver conversion patches (2-5) into patch 1 (Jakub)
---
 Documentation/networking/netmem.rst                    | 5 ++++-
 Documentation/translations/zh_CN/networking/netmem.rst | 4 +++-
 drivers/net/ethernet/broadcom/bnxt/bnxt.c              | 2 +-
 drivers/net/ethernet/google/gve/gve_main.c             | 2 +-
 drivers/net/ethernet/mellanox/mlx5/core/en_main.c      | 2 +-
 drivers/net/ethernet/meta/fbnic/fbnic_netdev.c         | 2 +-
 include/linux/netdevice.h                              | 7 ++++++-
 net/core/dev.c                                         | 2 +-
 net/core/netdev-genl.c                                 | 2 +-
 9 files changed, 19 insertions(+), 9 deletions(-)

diff --git a/Documentation/networking/netmem.rst b/Documentation/networking/netmem.rst
index b63aded46337..5ccadba4f373 100644
--- a/Documentation/networking/netmem.rst
+++ b/Documentation/networking/netmem.rst
@@ -95,4 +95,7 @@ Driver TX Requirements
    netdev@, or reach out to the maintainers and/or almasrymina@google.com for
    help adding the netmem API.
 
-2. Driver should declare support by setting `netdev->netmem_tx = true`
+2. Driver should declare support by setting `netdev->netmem_tx` to the
+   appropriate mode:
+
+   - `NETMEM_TX_DMA`: for physical devices that perform DMA.
diff --git a/Documentation/translations/zh_CN/networking/netmem.rst b/Documentation/translations/zh_CN/networking/netmem.rst
index fe351a240f02..9c84423b7528 100644
--- a/Documentation/translations/zh_CN/networking/netmem.rst
+++ b/Documentation/translations/zh_CN/networking/netmem.rst
@@ -89,4 +89,6 @@ dma-mapping API 去处理。
 使用某个还不存在的 netmem API，你可以自行添加并提交到 netdev@，也可以联系维护
 人员或者发送邮件至 almasrymina@google.com 寻求帮助。
 
-2. 驱动程序应通过设置 netdev->netmem_tx = true 来表明自身支持 netmem 功能。
+2. 驱动程序应将 `netdev->netmem_tx` 设置为适当的模式：
+
+   - `NETMEM_TX_DMA`：适用于执行 DMA 的物理设备。
diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt.c b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
index 8c55874f44ca..ed9c22dc4a5a 100644
--- a/drivers/net/ethernet/broadcom/bnxt/bnxt.c
+++ b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
@@ -17120,7 +17120,7 @@ static int bnxt_init_one(struct pci_dev *pdev, const struct pci_device_id *ent)
 	dev->queue_mgmt_ops = &bnxt_queue_mgmt_ops_unsupp;
 	if (BNXT_SUPPORTS_QUEUE_API(bp))
 		dev->queue_mgmt_ops = &bnxt_queue_mgmt_ops;
-	dev->netmem_tx = true;
+	dev->netmem_tx = NETMEM_TX_DMA;
 
 	rc = register_netdev(dev);
 	if (rc)
diff --git a/drivers/net/ethernet/google/gve/gve_main.c b/drivers/net/ethernet/google/gve/gve_main.c
index 424d973c97f2..dd2b8f087163 100644
--- a/drivers/net/ethernet/google/gve/gve_main.c
+++ b/drivers/net/ethernet/google/gve/gve_main.c
@@ -2894,7 +2894,7 @@ static int gve_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
 		goto abort_with_wq;
 
 	if (!gve_is_gqi(priv) && !gve_is_qpl(priv))
-		dev->netmem_tx = true;
+		dev->netmem_tx = NETMEM_TX_DMA;
 
 	err = register_netdev(dev);
 	if (err)
diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
index 5a46870c4b74..fc49aae38807 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
@@ -5924,7 +5924,7 @@ static void mlx5e_build_nic_netdev(struct net_device *netdev)
 
 	netdev->priv_flags       |= IFF_UNICAST_FLT;
 
-	netdev->netmem_tx = true;
+	netdev->netmem_tx = NETMEM_TX_DMA;
 
 	netif_set_tso_max_size(netdev, GSO_MAX_SIZE);
 	mlx5e_set_xdp_feature(priv);
diff --git a/drivers/net/ethernet/meta/fbnic/fbnic_netdev.c b/drivers/net/ethernet/meta/fbnic/fbnic_netdev.c
index c406a3b56b37..138e522ef9b9 100644
--- a/drivers/net/ethernet/meta/fbnic/fbnic_netdev.c
+++ b/drivers/net/ethernet/meta/fbnic/fbnic_netdev.c
@@ -752,7 +752,7 @@ struct net_device *fbnic_netdev_alloc(struct fbnic_dev *fbd)
 	netdev->netdev_ops = &fbnic_netdev_ops;
 	netdev->stat_ops = &fbnic_stat_ops;
 	netdev->queue_mgmt_ops = &fbnic_queue_mgmt_ops;
-	netdev->netmem_tx = true;
+	netdev->netmem_tx = NETMEM_TX_DMA;
 
 	fbnic_set_ethtool_ops(netdev);
 
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 0e1e581efc5a..a54a37fab8d9 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -1788,6 +1788,11 @@ enum netdev_stat_type {
 	NETDEV_PCPU_STAT_DSTATS, /* struct pcpu_dstats */
 };
 
+enum netmem_tx_mode {
+	NETMEM_TX_NONE,		/* no netmem TX support */
+	NETMEM_TX_DMA,		/* DMA-capable netmem TX (real HW) */
+};
+
 enum netdev_reg_state {
 	NETREG_UNINITIALIZED = 0,
 	NETREG_REGISTERED,	/* completed register_netdevice */
@@ -1809,7 +1814,7 @@ enum netdev_reg_state {
  *	@lltx:		device supports lockless Tx. Deprecated for real HW
  *			drivers. Mainly used by logical interfaces, such as
  *			bonding and tunnels
- *	@netmem_tx:	device support netmem_tx.
+ *	@netmem_tx:	device netmem TX mode
  *
  *	@name:	This is the first field of the "visible" part of this structure
  *		(i.e. as seen by users in the "Space.c" file).  It is the name
diff --git a/net/core/dev.c b/net/core/dev.c
index 06c195906231..fbe4c328a367 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -3996,7 +3996,7 @@ static struct sk_buff *validate_xmit_unreadable_skb(struct sk_buff *skb,
 	if (likely(skb_frags_readable(skb)))
 		goto out;
 
-	if (!dev->netmem_tx)
+	if (dev->netmem_tx == NETMEM_TX_NONE)
 		goto out_free;
 
 	shinfo = skb_shinfo(skb);
diff --git a/net/core/netdev-genl.c b/net/core/netdev-genl.c
index b8f6076d8007..4d2c49371cdb 100644
--- a/net/core/netdev-genl.c
+++ b/net/core/netdev-genl.c
@@ -1164,7 +1164,7 @@ int netdev_nl_bind_tx_doit(struct sk_buff *skb, struct genl_info *info)
 		goto err_unlock_netdev;
 	}
 
-	if (!netdev->netmem_tx) {
+	if (netdev->netmem_tx == NETMEM_TX_NONE) {
 		err = -EOPNOTSUPP;
 		NL_SET_ERR_MSG(info->extack,
 			       "Driver does not support netmem TX");

-- 
2.53.0-Meta