On Fri, 27 Mar 2020, John Donnelly wrote: > Hi, > > I am seeing this WARNING event with iommu=off when booting a DL380 > server with a 5.4.17 kernel. ... > The end result is this USB port is not configured when > dma_direct_map_page() is called and it returns return > DMA_MAPPING_ERROR; > > > When I boot the server with iommu=on I don’t see this sequence : ... > On an older kernel 5.3. flavor I am not seeing this behavior, and the usbhib devices appear as expected : I forgot to mention: Since you have one kernel where the WARNING occurs and one where it doesn't, you can use bisection to find the commit that was responsible for the change in behavior. If you care to go to the trouble... Alan Stern
