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Re: [Qemu-devel] [PATCH for-2.3] powerpc: fix -machine usb=no for newwor
Re: [Qemu-devel] [PATCH for-2.3] powerpc: fix -machine usb=no for newworld and pseries machines
Mon, 23 Mar 2015 21:11:23 +0100
Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.5.0
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 <address@hidden>
>>> 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
>> 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?
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
The second good reason is that it's a guest ABI change for the versioned
pSeries machines, and as such it breaks migration.