On 2025/2/7 0:54, Mina Almasry wrote: > On Tue, Feb 4, 2025 at 6:23 AM Yunsheng Lin <yunshenglin0825@xxxxxxxxx> wrote: >> >> On 1/28/2025 2:12 PM, Christoph Hellwig wrote: >>> On Mon, Jan 27, 2025 at 10:57:32AM +0800, Yunsheng Lin wrote: >>>> Note, the devmem patchset seems to make the bug harder to fix, >>>> and may make backporting harder too. As there is no actual user >>>> for the devmem and the fixing for devmem is unclear for now, >>>> this patch does not consider fixing the case for devmem yet. >>> >>> Is there another outstanding patchet? Or do you mean the existing >>> devmem code already merged? If that isn't actually used it should >>> be removed, but otherwise you need to fix it. >> >> The last time I checked, only the code for networking stack supporting >> the devmem had been merged. >> >> The first driver suppporting seems to be bnxt, which seems to be under >> review: >> https://lore.kernel.org/all/20241022162359.2713094-1-ap420073@xxxxxxxxx/ >> >> As my understanding, this should work for the devmem too if the devmem > >>From a quick look at this patch, it looks like you're handling > netmem/net_iovs in the implementation, so this implementation is > indeed considering netmem. I think the paragraph in the commit message > that Christoph is responding to should be deleted, because in recent > iterations you're handling netmem. > >> provide a ops to do the per-netmem dma unmapping >> It would be good that devmem people can have a look at it and see if >> this fix works for the specific page_pool mp provider. >> > > We set pool->dma_map==false for memory providers that do not need > mapping/unmapping, which you are checking in > __page_pool_release_page_dma. In page_pool_item_unmap(), it will return early when pool->mp_priv is set no matter pool->dma_map is set or not, that was why I had the above paragraph in the commit message. The question seems to be about whether net_devmem_unbind_dmabuf() might be called after driver has already unbound as it seems to be doing the DMA unmapping operation based on the device of netdev->dev.parent, and page_pool doesn't seems to have direct calling of net_devmem_unbind_dmabuf() related API. I am not able to find who and where is seting the netdev->dev.parent, but I guess the DMA API is also not allowed to be called on the device of netdev->dev.parent when the networking driver has unbound? >
