On 20-09-2017 13:31, Herbert Xu wrote: > Harsh Jain <Harsh@xxxxxxxxxxx> wrote: >> While debugging DMA mapping error in chelsio crypto driver we observed that when scatter/gather list received by driver has some entry with page->offset > 4096 (PAGE_SIZE). It starts giving DMA error. Without IOMMU it works fine. > This is not a bug. The network stack can and will feed us such > SG lists. > >> 2) It cannot be driver's responsibilty to update received sg entries to adjust offset and page >> because we are not the only one who directly uses received sg list. > No the driver must deal with this. Having said that, if we can > improve our driver helper interface to make this easier then we > should do that too. What we certainly shouldn't do is to take a > whack-a-mole approach like this patch does. Agreed,I added that patch for understanding purpose only. Today I referred other crypto driver for DMA related code. Most of them are using dma_map_sg except QAT. In QAT, They are first updating the Page address using offset then mapping each page in for loop with dma_map_single(0. I will try the same in chelsio driver will see the behavior. > > Cheers,
