On 26-09-2017 00:15, David Woodhouse wrote: > On Wed, 2017-09-20 at 16:01 +0800, 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. > Hm? Under what circumstances is the offset permitted to be > > PAGE_SIZE? Its random, Kernel API's don't check offset value after arithmetic operations like in "__skb_to_sgvec()", "scatterwalk_ffwd()".
