On Thu, 2017-04-27 at 10:24 +0200, Pavel Hrdina wrote:
You're technically correct[1]. However, piix3-uhci is another piece of Intel-derived hardware so in practice qemu-system-aarch64 is very unlikely to have it compiled in and most users will end up getting the error instead. Isn't the nec-xhci also Intel hardware, so the same would apply to that controller as well.
Not quite: Intel Corporation 82371SB PIIX3 USB [Natoma/Triton II] [8086:7020] NEC Corporation uPD720200 USB 3.0 Host Controller [1033:0194] The vendor for piix3-uhci is Intel Corporation, the vendor for nec-xhci is NEC Corporation. I guess both are unlikely to show up in actual aarch64 hardware, but the former is clearly x86-specific while the latter is somewhat more architecture-agnostic.
Moreover, this probably happens only for downstream builds of QEMU (most likely only RHEL/CentOS) as there is no configure option for that. QEMU has some default configs for different architectures but in upstream QEMU the set of UHCI usb controllers is enabled by default for aarch64.
The upstream QEMU configuration takes the kitchen sink approach, eg. qemu-system-ppc64 will include allwinner-ahci and other devices that clearly have no place in a ppc64 guest, so I don't think we should take that as an indication that piix-uhci is something anyone will want to reasonably use on aarch64 :) -- Andrea Bolognani / Red Hat / Virtualization