On 29.01.20 18:09, Christoph Hellwig wrote: > On Wed, Jan 29, 2020 at 06:07:14PM +0100, Christian Borntraeger wrote: >>> DMA can be done to NORMAL memory as well. >> >> Exactly. >> I think iucv uses GFP_DMA because z/VM needs those buffers to reside below 2GB (which is ZONA_DMA for s390). > > The normal way to allocate memory with addressing limits would be to > use dma_alloc_coherent and friends. Any chance to switch iucv over to > that? Or is there no device associated with it? There is not necessarily a device for that. It is a hypervisor interface (an instruction that is interpreted by z/VM). We do have the netiucv driver that creates a virtual nic, but there is also AF_IUCV which works without a device. But back to the original question: If we mark kmalloc caches as usercopy caches, we should do the same for DMA kmalloc caches. As outlined by Christoph, this has nothing to do with device DMA.
