On 23/03/2015 19:21, Alexander Graf wrote: > On 03/23/2015 07:20 PM, Marcel Apfelbaum wrote: >> On 03/23/2015 07:05 PM, Paolo Bonzini wrote: >>> Capture the explicit setting of "usb=no" into a separate bool, and >>> use it to skip the update of machine->usb in the board init function. >>> >>> Signed-off-by: Paolo Bonzini <pbonz...@redhat.com> >>> --- >>> hw/core/machine.c | 1 + >>> hw/ppc/mac_newworld.c | 2 +- >>> hw/ppc/spapr.c | 2 +- >>> include/hw/boards.h | 1 + >>> 4 files changed, 4 insertions(+), 2 deletions(-) >>> >>> diff --git a/hw/core/machine.c b/hw/core/machine.c >>> index cb1185a..25c45e6 100644 >>> --- a/hw/core/machine.c >>> +++ b/hw/core/machine.c >>> @@ -223,6 +223,7 @@ static void machine_set_usb(Object *obj, bool >>> value, Error **errp) >>> MachineState *ms = MACHINE(obj); >>> >>> ms->usb = value; >>> + ms->usb_disabled = !value; >> Maybe is too late now, but I really not like this pollution of >> MachineState >> with 'usb_disabled'. (Imagine we have this kind of fields for lots of >> objects and lots >> of corner cases...) >> I know it comes to solve a bug, but we talked about it in another mail >> thread and >> this change in semantics was approved. >> >> Let me explain *why* I don't like it. >> 1. We add an "usb_disabled" field to a base class (actually object) >> of all the machines and the only place it is interesting is >> for 2 machines on ppc.
So we do for kernel_irqchip_requested/allowed. Both approaches could be replaced by a tri-state on/off/auto. >> 2. Even for these 2 machines, the scenario of defaults=on and usb=off >> is not practical. Why? For example you could add a virtio-input device instead of a USB keyboard and mouse. > I'm personally fine either way, but I assumed that Paolo had a good > reason for writing the patch? Actually, two. One good reason is that no matter how you look at it, it's at least surprising and at worst a bug that "-machine usb=no" includes a default USB controller. The second good reason is that it's a guest ABI change for the versioned pSeries machines, and as such it breaks migration. Paolo
