Re: [PATCH net v3 2/2] net: stmmac: Stop Tx queue when (en|dis)abling XSK pools

[Nicolai Buchwitz <nb@tipi-net.de>]

Hi Kurt

On 13.10.2026 10:57, Kurt Kanzenbach wrote:
> When enabling or disabling XSK pools in parallel to Tx traffic, kernel
> crashes occur. For VLAN tagged frames that happens in stmmac_xmit() ->
> dwmac4_set_vlan_tag() and for normal frames in stmmac_xmit() ->
> dwmac4_set_addr(). Both of these functions access the Tx DMA 
> descriptors.
> 
> The XDP pool (en|dis)ablement frees and reallocates the Tx DMA 
> resources:
> 
>  stmmac_disable_tx_queue:
>    __free_dma_tx_desc_resources
> 
>  stmmac_enable_tx_queue:
>    __alloc_dma_tx_desc_resources
>    __init_dma_tx_desc_rings
> 
> NAPI is disabled during that allocation window, but the Tx queue is not
> stopped. Therefore, add the stopping of the Tx queue during the 
> enabling
> and disabling of XSK pools.
> 
> The issue can be easily reproduced by:
> 
>  1. Run iperf
>  2. Run application which opens an AF_XDP/ZC socket
> 
> Also add a dedicated queue check for the XDP Tx paths.
> 
> Fixes: 132c32ee5bc0 ("net: stmmac: Add TX via XDP zero-copy socket")
> Suggested-by: Nicolai Buchwitz <nb@tipi-net.de> # XDP Tx checks
> Signed-off-by: Kurt Kanzenbach <kurt@linutronix.de>

> [...]

Reviewed-by: Nicolai Buchwitz <nb@tipi-net.de>
Tested-by: Nicolai Buchwitz <nb@tipi-net.de> # stm32mp215

Thanks,
Nicolai