netdev - [PATCH iwl-net] i40e: Fix XDP program unloading while removing the driver

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Message-Id: <20240516164108.1482192-1-michal.kubiak@intel.com>
Date: Thu, 16 May 2024 18:41:08 +0200
From: Michal Kubiak <michal.kubiak@...el.com>
To: intel-wired-lan@...ts.osuosl.org
Cc: maciej.fijalkowski@...el.com,
	netdev@...r.kernel.org,
	Michal Kubiak <michal.kubiak@...el.com>,
	Wojciech Drewek <wojciech.drewek@...el.com>
Subject: [PATCH iwl-net] i40e: Fix XDP program unloading while removing the driver

The commit 6533e558c650 ("i40e: Fix reset path while removing
the driver") introduced a new PF state "__I40E_IN_REMOVE" to block
modifying the XDP program while the driver is being removed.
Unfortunately, such a change is useful only if the ".ndo_bpf()"
callback was called out of the rmmod context because unloading the
existing XDP program is also a part of driver removing procedure.
In other words, from the rmmod context the driver is expected to
unload the XDP program without reporting any errors. Otherwise,
the kernel warning with callstack is printed out to dmesg.

Example failing scenario:
 1. Load the i40e driver.
 2. Load the XDP program.
 3. Unload the i40e driver (using "rmmod" command).

Fix this by improving checks in ".ndo_bpf()" to determine if that
callback was called from the removing context and if the kernel
wants to unload the XDP program. Allow for unloading the XDP program
in such a case.

Fixes: 6533e558c650 ("i40e: Fix reset path while removing the driver")
Reviewed-by: Wojciech Drewek <wojciech.drewek@...el.com>
Signed-off-by: Michal Kubiak <michal.kubiak@...el.com>
---
 drivers/net/ethernet/intel/i40e/i40e_main.c | 19 ++++++++++++++-----
 1 file changed, 14 insertions(+), 5 deletions(-)

diff --git a/drivers/net/ethernet/intel/i40e/i40e_main.c b/drivers/net/ethernet/intel/i40e/i40e_main.c
index ffb9f9f15c52..19fc043e351f 100644
--- a/drivers/net/ethernet/intel/i40e/i40e_main.c
+++ b/drivers/net/ethernet/intel/i40e/i40e_main.c
@@ -13264,6 +13264,20 @@ static int i40e_xdp_setup(struct i40e_vsi *vsi, struct bpf_prog *prog,
 	bool need_reset;
 	int i;

+	/* Called from netdev unregister context. Unload the XDP program. */
+	if (vsi->netdev->reg_state == NETREG_UNREGISTERING) {
+		xdp_features_clear_redirect_target(vsi->netdev);
+		old_prog = xchg(&vsi->xdp_prog, NULL);
+		if (old_prog)
+			bpf_prog_put(old_prog);
+
+		return 0;
+	}
+
+	/* VSI shall be deleted in a moment, just return EINVAL */
+	if (test_bit(__I40E_IN_REMOVE, pf->state))
+		return -EINVAL;
+
 	/* Don't allow frames that span over multiple buffers */
 	if (vsi->netdev->mtu > frame_size - I40E_PACKET_HDR_PAD) {
 		NL_SET_ERR_MSG_MOD(extack, "MTU too large for linear frames and XDP prog does not support frags");
@@ -13272,14 +13286,9 @@ static int i40e_xdp_setup(struct i40e_vsi *vsi, struct bpf_prog *prog,

 	/* When turning XDP on->off/off->on we reset and rebuild the rings. */
 	need_reset = (i40e_enabled_xdp_vsi(vsi) != !!prog);
-
 	if (need_reset)
 		i40e_prep_for_reset(pf);

-	/* VSI shall be deleted in a moment, just return EINVAL */
-	if (test_bit(__I40E_IN_REMOVE, pf->state))
-		return -EINVAL;
-
 	old_prog = xchg(&vsi->xdp_prog, prog);

 	if (need_reset) {
-- 
2.33.1