Re: [Qemu-devel] Turning off default storage devices?

[Andy Lutomirski]

On Wed, Apr 9, 2014 at 4:53 PM, Peter Crosthwaite
<address@hidden> wrote:
> Hi Andy,
>
> On Thu, Apr 10, 2014 at 5:55 AM, Andy Lutomirski <address@hidden> wrote:
>> Currently, -M q35 boots linux quite a bit slower than the default
>> machine type.  This seems to be because it takes a few hundred ms to
>> determine that there's nothing attached to the AHCI controller.
>>
>> In virtio setups, there will probably never be anything attached to
>> the AHCI controller.  Would it be possible to add something like
>> -machine default_storage=off to turn off default storage devices?
>> This could include the AHCI on q35 and the cdrom and such on pc.
>>
>> There's precedent: -machine usb=off turns off the default USB
>> controllers, which is great for setups that use xhci.
>>
>
> Is there a more generic solution to your problem? Can you implement
> command line device removal in a non specific way and avoid having to
> invent AHCI or even "storage" specific arguments. You could
> considering bringing the xhci use case you mentioned under the same
> umbrella.

An option like -suppress-default-device foobar to turn off the device
named foobar would work, but what happens if that device is a bus?
Will this just cause QEMU to crash?  Maybe the machine code would have
to opt in to allowing this kind of suppression, and there could be a
general error of you try to suppress a device that can't be
suppressed.

I can try to code this up, but I know nothing about QEMU internals.
I'm just a user :)

--Andy