On Thu, 11 Apr 2019 20:25:01 +0200 (CEST) Sebastian Ott <sebott@xxxxxxxxxxxxx> wrote: > On Fri, 5 Apr 2019, Halil Pasic wrote: > > To support protected virtualization cio will need to make sure the > > memory used for communication with the hypervisor is DMA memory. > > > > Let us introduce a DMA pool to cio that will help us in allocating > > deallocating those chunks of memory. > > > > We use a gen_pool backed with DMA pages to avoid each allocation > > effectively wasting a page, as we typically allocate much less > > than PAGE_SIZE. > > I don't think we should use this global DMA pool. I guess it's OK for > stuff like airq (where we don't have a struct device at hand) but for > CCW we should use the device we have. Yes, this way we waste some memory > but all dma memory a device uses should fit in a page - so the wastage > is not too much. > Is what you envision an own gen_pool on for each subchannel (e.g. a struct io_subchannel member)? I'm struggling with understanding the expected benefits of a per-subchannel pool/allocator. Can you please tell me what benefits do you expect (over the current approach)? I understand you idea is to keep the CIO global pool for stuff that can not be tied to a single device (i.e. ariq). So the per device stuff would also mean more code. Would you be OK with postponing this alleged enhancement (i.e. implement it as a patch on top of this series)? Regards, Halil
