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Subject[PATCH AUTOSEL 5.4 33/58] net: ll_temac: Fix RX buffer descriptor handling on GFP_ATOMIC pressure
Date
From: Esben Haabendal <esben@geanix.com>

[ Upstream commit 770d9c67974c4c71af4beb786dc43162ad2a15ba ]

Failures caused by GFP_ATOMIC memory pressure have been observed, and
due to the missing error handling, results in kernel crash such as

[1876998.350133] kernel BUG at mm/slub.c:3952!
[1876998.350141] invalid opcode: 0000 [#1] PREEMPT SMP PTI
[1876998.350147] CPU: 2 PID: 0 Comm: swapper/2 Not tainted 5.3.0-scnxt #1
[1876998.350150] Hardware name: N/A N/A/COMe-bIP2, BIOS CCR2R920 03/01/2017
[1876998.350160] RIP: 0010:kfree+0x1ca/0x220
[1876998.350164] Code: 85 db 74 49 48 8b 95 68 01 00 00 48 31 c2 48 89 10 e9 d7 fe ff ff 49 8b 04 24 a9 00 00 01 00 75 0b 49 8b 44 24 08 a8 01 75 02 <0f> 0b 49 8b 04 24 31 f6 a9 00 00 01 00 74 06 41 0f b6 74 24
5b
[1876998.350172] RSP: 0018:ffffc900000f0df0 EFLAGS: 00010246
[1876998.350177] RAX: ffffea00027f0708 RBX: ffff888008d78000 RCX: 0000000000391372
[1876998.350181] RDX: 0000000000000000 RSI: ffffe8ffffd01400 RDI: ffff888008d78000
[1876998.350185] RBP: ffff8881185a5d00 R08: ffffc90000087dd8 R09: 000000000000280a
[1876998.350189] R10: 0000000000000002 R11: 0000000000000000 R12: ffffea0000235e00
[1876998.350193] R13: ffff8881185438a0 R14: 0000000000000000 R15: ffff888118543870
[1876998.350198] FS: 0000000000000000(0000) GS:ffff88811f300000(0000) knlGS:0000000000000000
[1876998.350203] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
s#1 Part1
[1876998.350206] CR2: 00007f8dac7b09f0 CR3: 000000011e20a006 CR4: 00000000001606e0
[1876998.350210] Call Trace:
[1876998.350215] <IRQ>
[1876998.350224] ? __netif_receive_skb_core+0x70a/0x920
[1876998.350229] kfree_skb+0x32/0xb0
[1876998.350234] __netif_receive_skb_core+0x70a/0x920
[1876998.350240] __netif_receive_skb_one_core+0x36/0x80
[1876998.350245] process_backlog+0x8b/0x150
[1876998.350250] net_rx_action+0xf7/0x340
[1876998.350255] __do_softirq+0x10f/0x353
[1876998.350262] irq_exit+0xb2/0xc0
[1876998.350265] do_IRQ+0x77/0xd0
[1876998.350271] common_interrupt+0xf/0xf
[1876998.350274] </IRQ>

In order to handle such failures more graceful, this change splits the
receive loop into one for consuming the received buffers, and one for
allocating new buffers.

When GFP_ATOMIC allocations fail, the receive will continue with the
buffers that is still there, and with the expectation that the allocations
will succeed in a later call to receive.

Fixes: 92744989533c ("net: add Xilinx ll_temac device driver")
Signed-off-by: Esben Haabendal <esben@geanix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/net/ethernet/xilinx/ll_temac.h | 1 +
drivers/net/ethernet/xilinx/ll_temac_main.c | 112 ++++++++++++++------
2 files changed, 82 insertions(+), 31 deletions(-)

diff --git a/drivers/net/ethernet/xilinx/ll_temac.h b/drivers/net/ethernet/xilinx/ll_temac.h
index 276292bca334d..99fe059e5c7f3 100644
--- a/drivers/net/ethernet/xilinx/ll_temac.h
+++ b/drivers/net/ethernet/xilinx/ll_temac.h
@@ -375,6 +375,7 @@ struct temac_local {
int tx_bd_next;
int tx_bd_tail;
int rx_bd_ci;
+ int rx_bd_tail;

/* DMA channel control setup */
u32 tx_chnl_ctrl;
diff --git a/drivers/net/ethernet/xilinx/ll_temac_main.c b/drivers/net/ethernet/xilinx/ll_temac_main.c
index fd4231493449b..2e3f59dae586e 100644
--- a/drivers/net/ethernet/xilinx/ll_temac_main.c
+++ b/drivers/net/ethernet/xilinx/ll_temac_main.c
@@ -389,12 +389,13 @@ static int temac_dma_bd_init(struct net_device *ndev)
lp->tx_bd_next = 0;
lp->tx_bd_tail = 0;
lp->rx_bd_ci = 0;
+ lp->rx_bd_tail = RX_BD_NUM - 1;

/* Enable RX DMA transfers */
wmb();
lp->dma_out(lp, RX_CURDESC_PTR, lp->rx_bd_p);
lp->dma_out(lp, RX_TAILDESC_PTR,
- lp->rx_bd_p + (sizeof(*lp->rx_bd_v) * (RX_BD_NUM - 1)));
+ lp->rx_bd_p + (sizeof(*lp->rx_bd_v) * lp->rx_bd_tail));

/* Prepare for TX DMA transfer */
lp->dma_out(lp, TX_CURDESC_PTR, lp->tx_bd_p);
@@ -923,27 +924,41 @@ temac_start_xmit(struct sk_buff *skb, struct net_device *ndev)
static void ll_temac_recv(struct net_device *ndev)
{
struct temac_local *lp = netdev_priv(ndev);
- struct sk_buff *skb, *new_skb;
- unsigned int bdstat;
- struct cdmac_bd *cur_p;
- dma_addr_t tail_p, skb_dma_addr;
- int length;
unsigned long flags;
+ int rx_bd;
+ bool update_tail = false;

spin_lock_irqsave(&lp->rx_lock, flags);

- tail_p = lp->rx_bd_p + sizeof(*lp->rx_bd_v) * lp->rx_bd_ci;
- cur_p = &lp->rx_bd_v[lp->rx_bd_ci];
-
- bdstat = be32_to_cpu(cur_p->app0);
- while ((bdstat & STS_CTRL_APP0_CMPLT)) {
+ /* Process all received buffers, passing them on network
+ * stack. After this, the buffer descriptors will be in an
+ * un-allocated stage, where no skb is allocated for it, and
+ * they are therefore not available for TEMAC/DMA.
+ */
+ do {
+ struct cdmac_bd *bd = &lp->rx_bd_v[lp->rx_bd_ci];
+ struct sk_buff *skb = lp->rx_skb[lp->rx_bd_ci];
+ unsigned int bdstat = be32_to_cpu(bd->app0);
+ int length;
+
+ /* While this should not normally happen, we can end
+ * here when GFP_ATOMIC allocations fail, and we
+ * therefore have un-allocated buffers.
+ */
+ if (!skb)
+ break;

- skb = lp->rx_skb[lp->rx_bd_ci];
- length = be32_to_cpu(cur_p->app4) & 0x3FFF;
+ /* Loop over all completed buffer descriptors */
+ if (!(bdstat & STS_CTRL_APP0_CMPLT))
+ break;

- dma_unmap_single(ndev->dev.parent, be32_to_cpu(cur_p->phys),
+ dma_unmap_single(ndev->dev.parent, be32_to_cpu(bd->phys),
XTE_MAX_JUMBO_FRAME_SIZE, DMA_FROM_DEVICE);
+ /* The buffer is not valid for DMA anymore */
+ bd->phys = 0;
+ bd->len = 0;

+ length = be32_to_cpu(bd->app4) & 0x3FFF;
skb_put(skb, length);
skb->protocol = eth_type_trans(skb, ndev);
skb_checksum_none_assert(skb);
@@ -958,39 +973,74 @@ static void ll_temac_recv(struct net_device *ndev)
* (back) for proper IP checksum byte order
* (be16).
*/
- skb->csum = htons(be32_to_cpu(cur_p->app3) & 0xFFFF);
+ skb->csum = htons(be32_to_cpu(bd->app3) & 0xFFFF);
skb->ip_summed = CHECKSUM_COMPLETE;
}

if (!skb_defer_rx_timestamp(skb))
netif_rx(skb);
+ /* The skb buffer is now owned by network stack above */
+ lp->rx_skb[lp->rx_bd_ci] = NULL;

ndev->stats.rx_packets++;
ndev->stats.rx_bytes += length;

- new_skb = netdev_alloc_skb_ip_align(ndev,
- XTE_MAX_JUMBO_FRAME_SIZE);
- if (!new_skb) {
- spin_unlock_irqrestore(&lp->rx_lock, flags);
- return;
+ rx_bd = lp->rx_bd_ci;
+ if (++lp->rx_bd_ci >= RX_BD_NUM)
+ lp->rx_bd_ci = 0;
+ } while (rx_bd != lp->rx_bd_tail);
+
+ /* Allocate new buffers for those buffer descriptors that were
+ * passed to network stack. Note that GFP_ATOMIC allocations
+ * can fail (e.g. when a larger burst of GFP_ATOMIC
+ * allocations occurs), so while we try to allocate all
+ * buffers in the same interrupt where they were processed, we
+ * continue with what we could get in case of allocation
+ * failure. Allocation of remaining buffers will be retried
+ * in following calls.
+ */
+ while (1) {
+ struct sk_buff *skb;
+ struct cdmac_bd *bd;
+ dma_addr_t skb_dma_addr;
+
+ rx_bd = lp->rx_bd_tail + 1;
+ if (rx_bd >= RX_BD_NUM)
+ rx_bd = 0;
+ bd = &lp->rx_bd_v[rx_bd];
+
+ if (bd->phys)
+ break; /* All skb's allocated */
+
+ skb = netdev_alloc_skb_ip_align(ndev, XTE_MAX_JUMBO_FRAME_SIZE);
+ if (!skb) {
+ dev_warn(&ndev->dev, "skb alloc failed\n");
+ break;
}

- cur_p->app0 = cpu_to_be32(STS_CTRL_APP0_IRQONEND);
- skb_dma_addr = dma_map_single(ndev->dev.parent, new_skb->data,
+ skb_dma_addr = dma_map_single(ndev->dev.parent, skb->data,
XTE_MAX_JUMBO_FRAME_SIZE,
DMA_FROM_DEVICE);
- cur_p->phys = cpu_to_be32(skb_dma_addr);
- cur_p->len = cpu_to_be32(XTE_MAX_JUMBO_FRAME_SIZE);
- lp->rx_skb[lp->rx_bd_ci] = new_skb;
+ if (WARN_ON_ONCE(dma_mapping_error(ndev->dev.parent,
+ skb_dma_addr))) {
+ dev_kfree_skb_any(skb);
+ break;
+ }

- lp->rx_bd_ci++;
- if (lp->rx_bd_ci >= RX_BD_NUM)
- lp->rx_bd_ci = 0;
+ bd->phys = cpu_to_be32(skb_dma_addr);
+ bd->len = cpu_to_be32(XTE_MAX_JUMBO_FRAME_SIZE);
+ bd->app0 = cpu_to_be32(STS_CTRL_APP0_IRQONEND);
+ lp->rx_skb[rx_bd] = skb;
+
+ lp->rx_bd_tail = rx_bd;
+ update_tail = true;
+ }

- cur_p = &lp->rx_bd_v[lp->rx_bd_ci];
- bdstat = be32_to_cpu(cur_p->app0);
+ /* Move tail pointer when buffers have been allocated */
+ if (update_tail) {
+ lp->dma_out(lp, RX_TAILDESC_PTR,
+ lp->rx_bd_p + sizeof(*lp->rx_bd_v) * lp->rx_bd_tail);
}
- lp->dma_out(lp, RX_TAILDESC_PTR, tail_p);

spin_unlock_irqrestore(&lp->rx_lock, flags);
}
--
2.20.1
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