On 04/17/2017 07:05 PM, Zengtao (B) wrote: > Hi Laura: > >> -----邮件原件----- >> 发件人: Laura Abbott [mailto:labbott@xxxxxxxxxx] >> 发送时间: 2017年4月18日 0:14 >> 收件人: Zengtao (B) <prime.zeng@xxxxxxxxxxxxx>; sumit.semwal@xxxxxxxxxx >> 抄送: gregkh@xxxxxxxxxxxxxxxxxxx; arve@xxxxxxxxxxx; >> riandrews@xxxxxxxxxxx; devel@xxxxxxxxxxxxxxxxxxxx; >> linux-kernel@xxxxxxxxxxxxxxx >> 主题: Re: Using ion memory for direct-io >> >> On 04/14/2017 02:18 AM, Zengtao (B) wrote: >>> Hi >>> >>> Currently, the ion mapped to userspace will be forced with VM_IO and >> VM_PFNMAP flags. >>> When I use the ion memory to do the direct-io, it will fail when >>> reaching the get_user_pages, >>> >>> Back to the VM_IO and VM_PFNMAP flag, there two flags are introduced >>> by the remap_pfn_range called by the ion_heap_mmap_user. >>> >>> From my point of view, all ion memory(cma/vmalloc/system heap) are >>> managed by linux vm, it is not reasonable to have the VM_IO and >>> VM_PFNMAP flag, but I don't any suitable function to replace the >> remap_pfn_range, any suggestions? >>> >>> Thanks && Regards >>> >>> Zengtao >>> >> >> The carveout heap is omitted from your list of 'all ion memory'. At one >> time, carveout memory was not backed by struct pages so I suspect >> this is a holdover from then. This would probably be better served > Yes, you are right, I missed the carveout heap which needs the VM_IO and VM_PFNMAP, > and I think the carveout heap can implement its own map_user rather then using the common > ion_heap_map_user. > The carveout heap only uses memory with struct pages these days. My point was that the VM_IO and VFM_PFNMAP shouldn't need to be used at all anymore. Sorry for the confusion. >> by using vm_insert_page and handling higher order pages properly. > Your latest patch has remove the the page faulting support, I didn't deep into the reason, > but I think this conflicts with the vm_insert_page. > vm_insert_page should be able to be used outside the fault handler. >> >> Thanks, >> Laura > > I tried to use the similar way as the dma framework do(split the page and map_vm_area), but > the split will break the ion sg design, maybe we need a new lowlevel map function instead of directly > using the remap_pfn_range. Yes, I don't think we can directly copy what the dma framework does. I think we should be okay with allocating pages with __GFP_COMP and then just using vm_insert_page but I'm not 100% sure this would work with CMA. For completeness sake, I know the request is for direct-io but can you share a few more details about the driver/use case where you want to use direct-io with Ion buffers? > > Thanks > Zengtao > Thanks, Laura _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
