| Message ID | 20211215202450.4086240-1-f.fainelli@gmail.com (mailing list archive) |
|---|---|
| State | Superseded |
| Commit | 8b8e6e782456f1ce02a7ae914bbd5b1053f0b034 |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | [net] net: systemport: Add global locking for descriptor lifecycle | expand |
Hello: This patch was applied to netdev/net.git (master) by Jakub Kicinski <kuba@kernel.org>: On Wed, 15 Dec 2021 12:24:49 -0800 you wrote: > The descriptor list is a shared resource across all of the transmit queues, and > the locking mechanism used today only protects concurrency across a given > transmit queue between the transmit and reclaiming. This creates an opportunity > for the SYSTEMPORT hardware to work on corrupted descriptors if we have > multiple producers at once which is the case when using multiple transmit > queues. > > [...] Here is the summary with links: - [net] net: systemport: Add global locking for descriptor lifecycle https://git.kernel.org/netdev/net/c/8b8e6e782456 You are awesome, thank you!
diff --git a/drivers/net/ethernet/broadcom/bcmsysport.c b/drivers/net/ethernet/broadcom/bcmsysport.c index 40933bf5a710..60dde29974bf 100644 --- a/drivers/net/ethernet/broadcom/bcmsysport.c +++ b/drivers/net/ethernet/broadcom/bcmsysport.c @@ -1309,11 +1309,11 @@ static netdev_tx_t bcm_sysport_xmit(struct sk_buff *skb, struct bcm_sysport_priv *priv = netdev_priv(dev); struct device *kdev = &priv->pdev->dev; struct bcm_sysport_tx_ring *ring; + unsigned long flags, desc_flags; struct bcm_sysport_cb *cb; struct netdev_queue *txq; u32 len_status, addr_lo; unsigned int skb_len; - unsigned long flags; dma_addr_t mapping; u16 queue; int ret; @@ -1373,8 +1373,10 @@ static netdev_tx_t bcm_sysport_xmit(struct sk_buff *skb, ring->desc_count--; /* Ports are latched, so write upper address first */ + spin_lock_irqsave(&priv->desc_lock, desc_flags); tdma_writel(priv, len_status, TDMA_WRITE_PORT_HI(ring->index)); tdma_writel(priv, addr_lo, TDMA_WRITE_PORT_LO(ring->index)); + spin_unlock_irqrestore(&priv->desc_lock, desc_flags); /* Check ring space and update SW control flow */ if (ring->desc_count == 0) @@ -2013,6 +2015,7 @@ static int bcm_sysport_open(struct net_device *dev) } /* Initialize both hardware and software ring */ + spin_lock_init(&priv->desc_lock); for (i = 0; i < dev->num_tx_queues; i++) { ret = bcm_sysport_init_tx_ring(priv, i); if (ret) { diff --git a/drivers/net/ethernet/broadcom/bcmsysport.h b/drivers/net/ethernet/broadcom/bcmsysport.h index 984f76e74b43..16b73bb9acc7 100644 --- a/drivers/net/ethernet/broadcom/bcmsysport.h +++ b/drivers/net/ethernet/broadcom/bcmsysport.h @@ -711,6 +711,7 @@ struct bcm_sysport_priv { int wol_irq; /* Transmit rings */ + spinlock_t desc_lock; struct bcm_sysport_tx_ring *tx_rings; /* Receive queue */
The descriptor list is a shared resource across all of the transmit queues, and the locking mechanism used today only protects concurrency across a given transmit queue between the transmit and reclaiming. This creates an opportunity for the SYSTEMPORT hardware to work on corrupted descriptors if we have multiple producers at once which is the case when using multiple transmit queues. This was particularly noticeable when using multiple flows/transmit queues and it showed up in interesting ways in that UDP packets would get a correct UDP header checksum being calculated over an incorrect packet length. Similarly TCP packets would get an equally correct checksum computed by the hardware over an incorrect packet length. The SYSTEMPORT hardware maintains an internal descriptor list that it re-arranges when the driver produces a new descriptor anytime it writes to the WRITE_PORT_{HI,LO} registers, there is however some delay in the hardware to re-organize its descriptors and it is possible that concurrent TX queues eventually break this internal allocation scheme to the point where the length/status part of the descriptor gets used for an incorrect data buffer. The fix is to impose a global serialization for all TX queues in the short section where we are writing to the WRITE_PORT_{HI,LO} registers which solves the corruption even with multiple concurrent TX queues being used. Fixes: 80105befdb4b ("net: systemport: add Broadcom SYSTEMPORT Ethernet MAC driver") Signed-off-by: Florian Fainelli <f.fainelli@gmail.com> --- drivers/net/ethernet/broadcom/bcmsysport.c | 5 ++++- drivers/net/ethernet/broadcom/bcmsysport.h | 1 + 2 files changed, 5 insertions(+), 1 deletion(-)