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Subject[PATCH 5.4 121/165] net/i40e: Fix concurrency issues between config flow and XSK
Date
From: Maxim Mikityanskiy <maximmi@mellanox.com>

[ Upstream commit b3873a5be757b44d51af542a50a6f2a3b6f95284 ]

Use synchronize_rcu to wait until the XSK wakeup function finishes
before destroying the resources it uses:

1. i40e_down already calls synchronize_rcu. On i40e_down either
__I40E_VSI_DOWN or __I40E_CONFIG_BUSY is set. Check the latter in
i40e_xsk_wakeup (the former is already checked there).

2. After switching the XDP program, call synchronize_rcu to let
i40e_xsk_wakeup exit before the XDP program is freed.

3. Changing the number of channels brings the interface down (see
i40e_prep_for_reset and i40e_pf_quiesce_all_vsi).

4. Disabling UMEM sets __I40E_CONFIG_BUSY, too.

Signed-off-by: Maxim Mikityanskiy <maximmi@mellanox.com>
Signed-off-by: Björn Töpel <bjorn.topel@intel.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20191217162023.16011-4-maximmi@mellanox.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/net/ethernet/intel/i40e/i40e.h | 2 +-
drivers/net/ethernet/intel/i40e/i40e_main.c | 10 +++++++---
drivers/net/ethernet/intel/i40e/i40e_xsk.c | 4 ++++
3 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/drivers/net/ethernet/intel/i40e/i40e.h b/drivers/net/ethernet/intel/i40e/i40e.h
index 2af9f6308f84..401304d4d553 100644
--- a/drivers/net/ethernet/intel/i40e/i40e.h
+++ b/drivers/net/ethernet/intel/i40e/i40e.h
@@ -1151,7 +1151,7 @@ void i40e_set_fec_in_flags(u8 fec_cfg, u32 *flags);

static inline bool i40e_enabled_xdp_vsi(struct i40e_vsi *vsi)
{
- return !!vsi->xdp_prog;
+ return !!READ_ONCE(vsi->xdp_prog);
}

int i40e_create_queue_channel(struct i40e_vsi *vsi, struct i40e_channel *ch);
diff --git a/drivers/net/ethernet/intel/i40e/i40e_main.c b/drivers/net/ethernet/intel/i40e/i40e_main.c
index 339925af0206..4960c9c3e773 100644
--- a/drivers/net/ethernet/intel/i40e/i40e_main.c
+++ b/drivers/net/ethernet/intel/i40e/i40e_main.c
@@ -6804,8 +6804,8 @@ void i40e_down(struct i40e_vsi *vsi)
for (i = 0; i < vsi->num_queue_pairs; i++) {
i40e_clean_tx_ring(vsi->tx_rings[i]);
if (i40e_enabled_xdp_vsi(vsi)) {
- /* Make sure that in-progress ndo_xdp_xmit
- * calls are completed.
+ /* Make sure that in-progress ndo_xdp_xmit and
+ * ndo_xsk_wakeup calls are completed.
*/
synchronize_rcu();
i40e_clean_tx_ring(vsi->xdp_rings[i]);
@@ -12526,8 +12526,12 @@ static int i40e_xdp_setup(struct i40e_vsi *vsi,

old_prog = xchg(&vsi->xdp_prog, prog);

- if (need_reset)
+ if (need_reset) {
+ if (!prog)
+ /* Wait until ndo_xsk_wakeup completes. */
+ synchronize_rcu();
i40e_reset_and_rebuild(pf, true, true);
+ }

for (i = 0; i < vsi->num_queue_pairs; i++)
WRITE_ONCE(vsi->rx_rings[i]->xdp_prog, vsi->xdp_prog);
diff --git a/drivers/net/ethernet/intel/i40e/i40e_xsk.c b/drivers/net/ethernet/intel/i40e/i40e_xsk.c
index d07e1a890428..f73cd917c44f 100644
--- a/drivers/net/ethernet/intel/i40e/i40e_xsk.c
+++ b/drivers/net/ethernet/intel/i40e/i40e_xsk.c
@@ -787,8 +787,12 @@ int i40e_xsk_wakeup(struct net_device *dev, u32 queue_id, u32 flags)
{
struct i40e_netdev_priv *np = netdev_priv(dev);
struct i40e_vsi *vsi = np->vsi;
+ struct i40e_pf *pf = vsi->back;
struct i40e_ring *ring;

+ if (test_bit(__I40E_CONFIG_BUSY, pf->state))
+ return -ENETDOWN;
+
if (test_bit(__I40E_VSI_DOWN, vsi->state))
return -ENETDOWN;

--
2.20.1


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