[PATCH net 0/3] bnxt_en: XDP redirect fixes

[PATCH net 0/3] bnxt_en: XDP redirect fixes

[Michael Chan]

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This series includes 3 fixes related to the XDP redirect code path in
the driver.  The first one adds locking when the number of TX XDP rings
is less than the number of CPUs.  The second one adjusts the maximum MTU
that can support XDP with enough tail room in the buffer.  The 3rd one
fixes a race condition between TX ring shutdown and the XDP redirect path.

Andy Gospodarek (1):
  bnxt_en: reserve space inside receive page for skb_shared_info

Pavan Chebbi (1):
  bnxt_en: Synchronize tx when xdp redirects happen on same ring

Ray Jui (1):
  bnxt_en: Prevent XDP redirect from running when stopping TX queue

 drivers/net/ethernet/broadcom/bnxt/bnxt.c     |  7 +++++++
 drivers/net/ethernet/broadcom/bnxt/bnxt.h     |  5 ++++-
 drivers/net/ethernet/broadcom/bnxt/bnxt_xdp.c | 14 ++++++++++++--
 drivers/net/ethernet/broadcom/bnxt/bnxt_xdp.h |  2 ++
 4 files changed, 25 insertions(+), 3 deletions(-)

-- 
2.18.1


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[PATCH net 1/3] bnxt_en: Synchronize tx when xdp redirects happen on same ring

[Michael Chan]

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From: Pavan Chebbi <pavan.chebbi@broadcom.com>

If there are more CPUs than the number of TX XDP rings, multiple XDP
redirects can select the same TX ring based on the CPU on which
XDP redirect is called.  Add locking when needed and use static
key to decide whether to take the lock.

Fixes: f18c2b77b2e4 ("bnxt_en: optimized XDP_REDIRECT support")
Signed-off-by: Pavan Chebbi <pavan.chebbi@broadcom.com>
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
---
 drivers/net/ethernet/broadcom/bnxt/bnxt.c     | 7 +++++++
 drivers/net/ethernet/broadcom/bnxt/bnxt.h     | 2 ++
 drivers/net/ethernet/broadcom/bnxt/bnxt_xdp.c | 8 ++++++++
 drivers/net/ethernet/broadcom/bnxt/bnxt_xdp.h | 2 ++
 4 files changed, 19 insertions(+)

diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt.c b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
index 1c28495875cf..874fad0a5cf8 100644
--- a/drivers/net/ethernet/broadcom/bnxt/bnxt.c
+++ b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
@@ -3253,6 +3253,7 @@ static int bnxt_alloc_tx_rings(struct bnxt *bp)
 		}
 		qidx = bp->tc_to_qidx[j];
 		ring->queue_id = bp->q_info[qidx].queue_id;
+		spin_lock_init(&txr->xdp_tx_lock);
 		if (i < bp->tx_nr_rings_xdp)
 			continue;
 		if (i % bp->tx_nr_rings_per_tc == (bp->tx_nr_rings_per_tc - 1))
@@ -10338,6 +10339,12 @@ static int __bnxt_open_nic(struct bnxt *bp, bool irq_re_init, bool link_re_init)
 	if (irq_re_init)
 		udp_tunnel_nic_reset_ntf(bp->dev);
 
+	if (bp->tx_nr_rings_xdp < num_possible_cpus()) {
+		if (!static_key_enabled(&bnxt_xdp_locking_key))
+			static_branch_enable(&bnxt_xdp_locking_key);
+	} else if (static_key_enabled(&bnxt_xdp_locking_key)) {
+		static_branch_disable(&bnxt_xdp_locking_key);
+	}
 	set_bit(BNXT_STATE_OPEN, &bp->state);
 	bnxt_enable_int(bp);
 	/* Enable TX queues */
diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt.h b/drivers/net/ethernet/broadcom/bnxt/bnxt.h
index 61aa3e8c5952..b4d3d051463b 100644
--- a/drivers/net/ethernet/broadcom/bnxt/bnxt.h
+++ b/drivers/net/ethernet/broadcom/bnxt/bnxt.h
@@ -800,6 +800,8 @@ struct bnxt_tx_ring_info {
 	u32			dev_state;
 
 	struct bnxt_ring_struct	tx_ring_struct;
+	/* Synchronize simultaneous xdp_xmit on same ring */
+	spinlock_t		xdp_tx_lock;
 };
 
 #define BNXT_LEGACY_COAL_CMPL_PARAMS					\
diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt_xdp.c b/drivers/net/ethernet/broadcom/bnxt/bnxt_xdp.c
index 52fad0fdeacf..c0541ff00ac8 100644
--- a/drivers/net/ethernet/broadcom/bnxt/bnxt_xdp.c
+++ b/drivers/net/ethernet/broadcom/bnxt/bnxt_xdp.c
@@ -20,6 +20,8 @@
 #include "bnxt.h"
 #include "bnxt_xdp.h"
 
+DEFINE_STATIC_KEY_FALSE(bnxt_xdp_locking_key);
+
 struct bnxt_sw_tx_bd *bnxt_xmit_bd(struct bnxt *bp,
 				   struct bnxt_tx_ring_info *txr,
 				   dma_addr_t mapping, u32 len)
@@ -227,6 +229,9 @@ int bnxt_xdp_xmit(struct net_device *dev, int num_frames,
 	ring = smp_processor_id() % bp->tx_nr_rings_xdp;
 	txr = &bp->tx_ring[ring];
 
+	if (static_branch_unlikely(&bnxt_xdp_locking_key))
+		spin_lock(&txr->xdp_tx_lock);
+
 	for (i = 0; i < num_frames; i++) {
 		struct xdp_frame *xdp = frames[i];
 
@@ -250,6 +255,9 @@ int bnxt_xdp_xmit(struct net_device *dev, int num_frames,
 		bnxt_db_write(bp, &txr->tx_db, txr->tx_prod);
 	}
 
+	if (static_branch_unlikely(&bnxt_xdp_locking_key))
+		spin_unlock(&txr->xdp_tx_lock);
+
 	return nxmit;
 }
 
diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt_xdp.h b/drivers/net/ethernet/broadcom/bnxt/bnxt_xdp.h
index 0df40c3beb05..067bb5e821f5 100644
--- a/drivers/net/ethernet/broadcom/bnxt/bnxt_xdp.h
+++ b/drivers/net/ethernet/broadcom/bnxt/bnxt_xdp.h
@@ -10,6 +10,8 @@
 #ifndef BNXT_XDP_H
 #define BNXT_XDP_H
 
+DECLARE_STATIC_KEY_FALSE(bnxt_xdp_locking_key);
+
 struct bnxt_sw_tx_bd *bnxt_xmit_bd(struct bnxt *bp,
 				   struct bnxt_tx_ring_info *txr,
 				   dma_addr_t mapping, u32 len);
-- 
2.18.1


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[PATCH net 2/3] bnxt_en: reserve space inside receive page for skb_shared_info

[Michael Chan]

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From: Andy Gospodarek <gospo@broadcom.com>

Insufficient space was being reserved in the page used for packet
reception, so the interface MTU could be set too large to still have
room for the contents of the packet when doing XDP redirect.  This
resulted in the following message when redirecting a packet between
3520 and 3822 bytes with an MTU of 3822:

[311815.561880] XDP_WARN: xdp_update_frame_from_buff(line:200): Driver BUG: missing reserved tailroom

Fixes: f18c2b77b2e4 ("bnxt_en: optimized XDP_REDIRECT support")
Reviewed-by: Somnath Kotur <somnath.kotur@broadcom.com>
Reviewed-by: Pavan Chebbi <pavan.chebbi@broadcom.com>
Signed-off-by: Andy Gospodarek <gospo@broadcom.com>
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
---
 drivers/net/ethernet/broadcom/bnxt/bnxt.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt.h b/drivers/net/ethernet/broadcom/bnxt/bnxt.h
index b4d3d051463b..98453a78cbd0 100644
--- a/drivers/net/ethernet/broadcom/bnxt/bnxt.h
+++ b/drivers/net/ethernet/broadcom/bnxt/bnxt.h
@@ -593,7 +593,8 @@ struct nqe_cn {
 #define BNXT_MAX_MTU		9500
 #define BNXT_MAX_PAGE_MODE_MTU	\
 	((unsigned int)PAGE_SIZE - VLAN_ETH_HLEN - NET_IP_ALIGN -	\
-	 XDP_PACKET_HEADROOM)
+	 XDP_PACKET_HEADROOM - \
+	 SKB_DATA_ALIGN((unsigned int)sizeof(struct skb_shared_info)))
 
 #define BNXT_MIN_PKT_SIZE	52
 
-- 
2.18.1


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[PATCH net 3/3] bnxt_en: Prevent XDP redirect from running when stopping TX queue

[Michael Chan]

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From: Ray Jui <ray.jui@broadcom.com>

Add checks in the XDP redirect callback to prevent XDP from running when
the TX ring is undergoing shutdown.

Also remove redundant checks in the XDP redirect callback to validate the
txr and the flag that indicates the ring supports XDP. The modulo
arithmetic on 'tx_nr_rings_xdp' already guarantees the derived TX
ring is an XDP ring.  txr is also guaranteed to be valid after checking
BNXT_STATE_OPEN and within RCU grace period.

Fixes: f18c2b77b2e4 ("bnxt_en: optimized XDP_REDIRECT support")
Reviewed-by: Vladimir Olovyannikov <vladimir.olovyannikov@broadcom.com>
Signed-off-by: Ray Jui <ray.jui@broadcom.com>
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
---
 drivers/net/ethernet/broadcom/bnxt/bnxt_xdp.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt_xdp.c b/drivers/net/ethernet/broadcom/bnxt/bnxt_xdp.c
index c0541ff00ac8..03b1d6c04504 100644
--- a/drivers/net/ethernet/broadcom/bnxt/bnxt_xdp.c
+++ b/drivers/net/ethernet/broadcom/bnxt/bnxt_xdp.c
@@ -229,14 +229,16 @@ int bnxt_xdp_xmit(struct net_device *dev, int num_frames,
 	ring = smp_processor_id() % bp->tx_nr_rings_xdp;
 	txr = &bp->tx_ring[ring];
 
+	if (READ_ONCE(txr->dev_state) == BNXT_DEV_STATE_CLOSING)
+		return -EINVAL;
+
 	if (static_branch_unlikely(&bnxt_xdp_locking_key))
 		spin_lock(&txr->xdp_tx_lock);
 
 	for (i = 0; i < num_frames; i++) {
 		struct xdp_frame *xdp = frames[i];
 
-		if (!txr || !bnxt_tx_avail(bp, txr) ||
-		    !(bp->bnapi[ring]->flags & BNXT_NAPI_FLAG_XDP))
+		if (!bnxt_tx_avail(bp, txr))
 			break;
 
 		mapping = dma_map_single(&pdev->dev, xdp->data, xdp->len,
-- 
2.18.1


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Re: [PATCH net 0/3] bnxt_en: XDP redirect fixes

[patchwork-bot+netdevbpf]

Hello:

This series was applied to netdev/net.git (master)
by David S. Miller <davem@davemloft.net>:

On Fri,  1 Apr 2022 20:21:09 -0400 you wrote:
> This series includes 3 fixes related to the XDP redirect code path in
> the driver.  The first one adds locking when the number of TX XDP rings
> is less than the number of CPUs.  The second one adjusts the maximum MTU
> that can support XDP with enough tail room in the buffer.  The 3rd one
> fixes a race condition between TX ring shutdown and the XDP redirect path.
> 
> Andy Gospodarek (1):
>   bnxt_en: reserve space inside receive page for skb_shared_info
> 
> [...]

Here is the summary with links:
  - [net,1/3] bnxt_en: Synchronize tx when xdp redirects happen on same ring
    https://git.kernel.org/netdev/net/c/4f81def272de
  - [net,2/3] bnxt_en: reserve space inside receive page for skb_shared_info
    https://git.kernel.org/netdev/net/c/facc173cf700
  - [net,3/3] bnxt_en: Prevent XDP redirect from running when stopping TX queue
    https://git.kernel.org/netdev/net/c/27d4073f8d9a

You are awesome, thank you!
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