Re: [Qemu-devel] [SeaBIOS] [PATCH] don't expose pvpanic device in the UI

[Markus Armbruster]

Andreas Färber <address@hidden> writes:

> Am 06.08.2013 10:36, schrieb Gleb Natapov:
>> On Tue, Aug 06, 2013 at 11:33:10AM +0300, Michael S. Tsirkin wrote:
>>> On Tue, Aug 06, 2013 at 10:21:52AM +0300, Gleb Natapov wrote:
>>>>> If you see a mouse in a room, how likely is it that there's
>>>>> a single mouse there?
>>>>>
>>>>> This is a PV technology which to me looks like it was
>>>>> rushed through and not only set on by default, but
>>>>> without a way to disable it - apparently on the assumption
>>>>> there's 0 chance it can cause any damage. Now that
>>>>> we do know the chance it's not there, why not go back
>>>>> to the standard interface, and why not give
>>>>> users a chance to enable/disable it?
>>>> You should be able to disable it with: -device pvpanic,ioport=0
>>>
>>> Doesn't work for me.
>> Bug that should be fixed. With this command line _STA should return
>> zero.
>> 
>>> Besides, both -device pvpanic and use of ioport=0 to disable it
>>> are completely undocumented.
>>>
>> Not the only undocumented thing in QEMU command line :)
> [snip]
>
> I disagree: -device adds a device, not removes one. It will still be
> present.
>
> I am neutral as to whether qemu-system-x86_64 should have it enabled by
> default or not.

Me too.

>                 But if we want to suppress it, then -nodefaults should
> disable it.

ACK: that's how we do optional devices that are there by default.

ioport=0 affecting _STA is *not* "removing" the device, it's changing
how the device is exposed to the guest.  No opinion on whether it's a
good idea or not.

>             Since libvirt uses that though, it would mean libvirt would
> need to add it back, whether via user's XML domain config or by libvirt
> itself based on some version/etc. heuristics.

Doubt that'll be a problem for libvirt.