Re: [PATCH iwl-net v2 1/2] e1000e: fix Rx skb DMA map error sentinel

["Kadosh, MoriyaX" <moriyax.kadosh@intel.com>]

On 05/10/2026 21:11, Ruinskiy, Dima wrote:
> On 13/09/2026 20:15, Matt Vollrath wrote:
>> Upon encountering a DMA_MAPPING_ERROR during skb allocation and mapping,
>> the driver would leave DMA_MAPPING_ERROR in the buffer_info->dma field.
>> This would lead several buffer_info->dma == 0 conditions down unwanted
>> paths:
>>
>> * In e1000_alloc_jumbo_rx_buffers(), it would not re-attempt the failed
>>    mapping and instead write DMA_MAPPING_ERROR to the h/w descriptor on
>>    the next allocation call. On cleaning or teardown it would attempt to
>>    dma_unmap_page() DMA_MAPPING_ERROR. This case would only be
>>    reachable at MTU > 1518 and page size > 16K.
>> * In e1000_clean_rx_ring(), it would attempt to dma_unmap_page/single()
>>    DMA_MAPPING_ERROR (unless cleaned by the jumbo path first). This case
>>    would be reachable at any combination of MTU and page size.
>>
>> Use buffer_info->dma = 0 as the sentinel for "DMA is not mapped." Set it
>> immediately upon detecting the failure.
>>
>> The map error value was 0 on some platforms (including most common x86)
>> until error values were unified to DMA_MAPPING_ERROR in v4.20/v5.0.
>> Since then the error handling in this driver has been incorrect on all
>> platforms.
>>
>> Signed-off-by: Matt Vollrath <tactii@gmail.com>
>> Suggested-by: Jakub Kicinski <kuba@kernel.org>
>> Fixes: bc7f75fa9788 ("[E1000E]: New pci-express e1000 driver 
>> (currently for ICH9 devices only)")
>> Cc: stable@vger.kernel.org
>> ---
>> v2:
>> * Add history blurb to description.
>> ---
>>   drivers/net/ethernet/intel/e1000e/netdev.c | 3 +++
>>   1 file changed, 3 insertions(+)
>>
>> diff --git a/drivers/net/ethernet/intel/e1000e/netdev.c b/drivers/net/ 
>> ethernet/intel/e1000e/netdev.c
>> index 844f31ab37ad..26f45ee8c7e7 100644
>> --- a/drivers/net/ethernet/intel/e1000e/netdev.c
>> +++ b/drivers/net/ethernet/intel/e1000e/netdev.c
>> @@ -691,6 +691,7 @@ static void e1000_alloc_rx_buffers(struct 
>> e1000_ring *rx_ring,
>>                             adapter->rx_buffer_len,
>>                             DMA_FROM_DEVICE);
>>           if (dma_mapping_error(&pdev->dev, buffer_info->dma)) {
>> +            buffer_info->dma = 0;
>>               dev_err(&pdev->dev, "Rx DMA map failed\n");
>>               adapter->rx_dma_failed++;
>>               break;
>> @@ -791,6 +792,7 @@ static void e1000_alloc_rx_buffers_ps(struct 
>> e1000_ring *rx_ring,
>>                             adapter->rx_ps_bsize0,
>>                             DMA_FROM_DEVICE);
>>           if (dma_mapping_error(&pdev->dev, buffer_info->dma)) {
>> +            buffer_info->dma = 0;
>>               dev_err(&pdev->dev, "Rx DMA map failed\n");
>>               adapter->rx_dma_failed++;
>>               /* cleanup skb */
>> @@ -877,6 +879,7 @@ static void e1000_alloc_jumbo_rx_buffers(struct 
>> e1000_ring *rx_ring,
>>                               PAGE_SIZE,
>>                               DMA_FROM_DEVICE);
>>               if (dma_mapping_error(&pdev->dev, buffer_info->dma)) {
>> +                buffer_info->dma = 0;
>>                   adapter->alloc_rx_buff_failed++;
>>                   break;
>>               }
>>
>> base-commit: 78445023439506ebd83b86d40b1e428a3b309d4a
> Reviewed-by: Dima Ruinskiy <dima.ruinskiy@intel.com>
Tested-by: Moriya Kadosh <moriyax.kadosh@intel.com>