| Message ID | 20250314061353.106194-3-quic_miaoqing@quicinc.com (mailing list archive) |
|---|---|
| State | New |
| Delegated to: | Jeff Johnson |
| Headers | show |
| Series | wifi: ath11k: fix HTC rx insufficient length | expand |
On Fri, Mar 14, 2025 at 02:13:53PM +0800, Miaoqing Pan wrote: > A relatively unusual race condition occurs between host software > and hardware, where the host sees the updated destination ring head > pointer before the hardware updates the corresponding descriptor. > When this situation occurs, the length of the descriptor returns 0. > > The current error handling method is to increment descriptor tail > pointer by 1, but 'sw_index' is not updated, causing descriptor and > skb to not correspond one-to-one, resulting in the following error: > > ath11k_pci 0006:01:00.0: HTC Rx: insufficient length, got 1488, expected 1492 > ath11k_pci 0006:01:00.0: HTC Rx: insufficient length, got 1460, expected 1484 > > To address this problem and work around the broken hardware, > temporarily skip processing the current descriptor and handle it > again next time. However, to prevent this descriptor from > continuously returning 0, use the skb control block (cb) to set > a flag. If the length returns 0 again, this descriptor will be > discarded. > > Tested-on: QCA6698AQ hw2.1 PCI WLAN.HSP.1.1-04546-QCAHSPSWPL_V1_V2_SILICONZ_IOE-1 > > Reported-by: Johan Hovold <johan+linaro@kernel.org> > Closes: https://bugzilla.kernel.org/show_bug.cgi?id=218623 > Signed-off-by: Miaoqing Pan <quic_miaoqing@quicinc.com> > @@ -387,18 +387,36 @@ static int ath11k_ce_completed_recv_next(struct ath11k_ce_pipe *pipe, > > ath11k_hal_srng_access_begin(ab, srng); > > - desc = ath11k_hal_srng_dst_get_next_entry(ab, srng); > + desc = ath11k_hal_srng_dst_peek(ab, srng); > if (!desc) { > ret = -EIO; > goto err; > } > > *nbytes = ath11k_hal_ce_dst_status_get_length(desc); As I mentioned elsewhere, this function also sets the length field in the descriptor to zero. So if there's a racing update, you may never see the updated length. > - if (*nbytes == 0) { > - ret = -EIO; > - goto err; > + if (unlikely(*nbytes == 0)) { > + struct ath11k_skb_rxcb *rxcb = > + ATH11K_SKB_RXCB(pipe->dest_ring->skb[sw_index]); > + > + /* A relatively unusual race condition occurs between host > + * software and hardware, where the host sees the updated > + * destination ring head pointer before the hardware updates > + * the corresponding descriptor. > + * > + * Temporarily skip processing the current descriptor and handle > + * it again next time. However, to prevent this descriptor from > + * continuously returning 0, set 'is_desc_len0' flag. If the > + * length returns 0 again, this descriptor will be discarded. > + */ > + if (!rxcb->is_desc_len0) { > + rxcb->is_desc_len0 = true; > + ret = -EIO; > + goto err; > + } If you add the memory barrier and make sure not to clear the length field above, do you still see the length sometimes always reading zero if you retry more than once (i.e. drop the is_desc_len0 flag)? Perhaps the device is really passing you a zero-length descriptor that can simply be discarded straight away? Johan
On 3/14/2025 4:20 PM, Johan Hovold wrote: > On Fri, Mar 14, 2025 at 02:13:53PM +0800, Miaoqing Pan wrote: >> A relatively unusual race condition occurs between host software >> and hardware, where the host sees the updated destination ring head >> pointer before the hardware updates the corresponding descriptor. >> When this situation occurs, the length of the descriptor returns 0. >> >> The current error handling method is to increment descriptor tail >> pointer by 1, but 'sw_index' is not updated, causing descriptor and >> skb to not correspond one-to-one, resulting in the following error: >> >> ath11k_pci 0006:01:00.0: HTC Rx: insufficient length, got 1488, expected 1492 >> ath11k_pci 0006:01:00.0: HTC Rx: insufficient length, got 1460, expected 1484 >> >> To address this problem and work around the broken hardware, >> temporarily skip processing the current descriptor and handle it >> again next time. However, to prevent this descriptor from >> continuously returning 0, use the skb control block (cb) to set >> a flag. If the length returns 0 again, this descriptor will be >> discarded. >> >> Tested-on: QCA6698AQ hw2.1 PCI WLAN.HSP.1.1-04546-QCAHSPSWPL_V1_V2_SILICONZ_IOE-1 >> >> Reported-by: Johan Hovold <johan+linaro@kernel.org> >> Closes: https://bugzilla.kernel.org/show_bug.cgi?id=218623 >> Signed-off-by: Miaoqing Pan <quic_miaoqing@quicinc.com> > >> @@ -387,18 +387,36 @@ static int ath11k_ce_completed_recv_next(struct ath11k_ce_pipe *pipe, >> >> ath11k_hal_srng_access_begin(ab, srng); >> >> - desc = ath11k_hal_srng_dst_get_next_entry(ab, srng); >> + desc = ath11k_hal_srng_dst_peek(ab, srng); >> if (!desc) { >> ret = -EIO; >> goto err; >> } >> >> *nbytes = ath11k_hal_ce_dst_status_get_length(desc); > > As I mentioned elsewhere, this function also sets the length field in > the descriptor to zero. So if there's a racing update, you may never see > the updated length. > Will add below check. --- a/drivers/net/wireless/ath/ath11k/hal.c +++ b/drivers/net/wireless/ath/ath11k/hal.c @@ -602,7 +602,11 @@ u32 ath11k_hal_ce_dst_status_get_length(void *buf) u32 len; len = FIELD_GET(HAL_CE_DST_STATUS_DESC_FLAGS_LEN, desc->flags); - desc->flags &= ~HAL_CE_DST_STATUS_DESC_FLAGS_LEN; + /* Avoid setting the length field in the descriptor to zero when length + * is 0, as there's a racing update, may never see the updated length. + */ + if (likely(len)) + desc->flags &= ~HAL_CE_DST_STATUS_DESC_FLAGS_LEN; >> - if (*nbytes == 0) { >> - ret = -EIO; >> - goto err; >> + if (unlikely(*nbytes == 0)) { >> + struct ath11k_skb_rxcb *rxcb = >> + ATH11K_SKB_RXCB(pipe->dest_ring->skb[sw_index]); >> + >> + /* A relatively unusual race condition occurs between host >> + * software and hardware, where the host sees the updated >> + * destination ring head pointer before the hardware updates >> + * the corresponding descriptor. >> + * >> + * Temporarily skip processing the current descriptor and handle >> + * it again next time. However, to prevent this descriptor from >> + * continuously returning 0, set 'is_desc_len0' flag. If the >> + * length returns 0 again, this descriptor will be discarded. >> + */ >> + if (!rxcb->is_desc_len0) { >> + rxcb->is_desc_len0 = true; >> + ret = -EIO; >> + goto err; >> + } > > If you add the memory barrier and make sure not to clear the length > field above, do you still see the length sometimes always reading zero > if you retry more than once (i.e. drop the is_desc_len0 flag)? > > Perhaps the device is really passing you a zero-length descriptor that > can simply be discarded straight away? > > Johan Will verify your suggestion, thanks.
diff --git a/drivers/net/wireless/ath/ath11k/ce.c b/drivers/net/wireless/ath/ath11k/ce.c index e66e86bdec20..ccaf9b7a6857 100644 --- a/drivers/net/wireless/ath/ath11k/ce.c +++ b/drivers/net/wireless/ath/ath11k/ce.c @@ -1,7 +1,7 @@ // SPDX-License-Identifier: BSD-3-Clause-Clear /* * Copyright (c) 2018-2019 The Linux Foundation. All rights reserved. - * Copyright (c) 2021-2023 Qualcomm Innovation Center, Inc. All rights reserved. + * Copyright (c) 2021-2023, 2025 Qualcomm Innovation Center, Inc. All rights reserved. */ #include "dp_rx.h" @@ -387,18 +387,36 @@ static int ath11k_ce_completed_recv_next(struct ath11k_ce_pipe *pipe, ath11k_hal_srng_access_begin(ab, srng); - desc = ath11k_hal_srng_dst_get_next_entry(ab, srng); + desc = ath11k_hal_srng_dst_peek(ab, srng); if (!desc) { ret = -EIO; goto err; } *nbytes = ath11k_hal_ce_dst_status_get_length(desc); - if (*nbytes == 0) { - ret = -EIO; - goto err; + if (unlikely(*nbytes == 0)) { + struct ath11k_skb_rxcb *rxcb = + ATH11K_SKB_RXCB(pipe->dest_ring->skb[sw_index]); + + /* A relatively unusual race condition occurs between host + * software and hardware, where the host sees the updated + * destination ring head pointer before the hardware updates + * the corresponding descriptor. + * + * Temporarily skip processing the current descriptor and handle + * it again next time. However, to prevent this descriptor from + * continuously returning 0, set 'is_desc_len0' flag. If the + * length returns 0 again, this descriptor will be discarded. + */ + if (!rxcb->is_desc_len0) { + rxcb->is_desc_len0 = true; + ret = -EIO; + goto err; + } } + ath11k_hal_srng_dst_next(ab, srng); + *skb = pipe->dest_ring->skb[sw_index]; pipe->dest_ring->skb[sw_index] = NULL; @@ -430,9 +448,13 @@ static void ath11k_ce_recv_process_cb(struct ath11k_ce_pipe *pipe) dma_unmap_single(ab->dev, ATH11K_SKB_RXCB(skb)->paddr, max_nbytes, DMA_FROM_DEVICE); - if (unlikely(max_nbytes < nbytes)) { - ath11k_warn(ab, "rxed more than expected (nbytes %d, max %d)", - nbytes, max_nbytes); + if (unlikely(max_nbytes < nbytes || !nbytes)) { + if (nbytes) + ath11k_warn(ab, "rxed more than expected (nbytes %d, max %d)\n", + nbytes, max_nbytes); + else + ath11k_dbg(ab, ATH11K_DBG_CE, "rxed zero-length\n"); + dev_kfree_skb_any(skb); continue; } diff --git a/drivers/net/wireless/ath/ath11k/core.h b/drivers/net/wireless/ath/ath11k/core.h index 1a3d0de4afde..c8614c5c6493 100644 --- a/drivers/net/wireless/ath/ath11k/core.h +++ b/drivers/net/wireless/ath/ath11k/core.h @@ -128,6 +128,7 @@ struct ath11k_skb_rxcb { bool is_continuation; bool is_mcbc; bool is_eapol; + bool is_desc_len0; struct hal_rx_desc *rx_desc; u8 err_rel_src; u8 err_code;
A relatively unusual race condition occurs between host software and hardware, where the host sees the updated destination ring head pointer before the hardware updates the corresponding descriptor. When this situation occurs, the length of the descriptor returns 0. The current error handling method is to increment descriptor tail pointer by 1, but 'sw_index' is not updated, causing descriptor and skb to not correspond one-to-one, resulting in the following error: ath11k_pci 0006:01:00.0: HTC Rx: insufficient length, got 1488, expected 1492 ath11k_pci 0006:01:00.0: HTC Rx: insufficient length, got 1460, expected 1484 To address this problem and work around the broken hardware, temporarily skip processing the current descriptor and handle it again next time. However, to prevent this descriptor from continuously returning 0, use the skb control block (cb) to set a flag. If the length returns 0 again, this descriptor will be discarded. Tested-on: QCA6698AQ hw2.1 PCI WLAN.HSP.1.1-04546-QCAHSPSWPL_V1_V2_SILICONZ_IOE-1 Reported-by: Johan Hovold <johan+linaro@kernel.org> Closes: https://bugzilla.kernel.org/show_bug.cgi?id=218623 Signed-off-by: Miaoqing Pan <quic_miaoqing@quicinc.com> --- drivers/net/wireless/ath/ath11k/ce.c | 38 ++++++++++++++++++++------ drivers/net/wireless/ath/ath11k/core.h | 1 + 2 files changed, 31 insertions(+), 8 deletions(-)