[fedora-arm] f21 + qemu requires manually passing a dtb?

[Cole Robinson]

On 11/19/2014 10:23 AM, Peter Robinson wrote:
>>>>> Just trying the F21 beta (and Fedora-Minimal-armhfp-21-20141117-sda.raw)
>>>>> under
>>>>> qemu. Seems like these versions both require explicitly passing in a dtb
>>>>> to
>>>>> qemu to actually boot. Well, maybe it's booting and I'm just not getting
>>>>> any
>>>>> serial output, can't really tell.
>>>>>
>>>>> Passing a dtb to qemu wasn't required for the F20 GA release at least,
>>>>> and
>>>>> still isn't required with F21 qemu-system-arm, so presumably it's not a
>>>>> qemu
>>>>> regression.
>>>
>>>
>>> Fedora 21 requires the use of a dtb to boot the multiplatform kernel. This
>>> changed
>>> around the 3.16 RC's (iirc).
>>>
>>>>>
>>>>> Having to pass a dtb is kind of a pain for management tools, it's
>>>>> another
>>>>> file
>>>>> that needs to handled. And the docs say it shouldn't be required:
>>>>>
>>>>> https://fedoraproject.org/wiki/Architectures/ARM/F21/Installation#For_Versatile_Express_Emulation_with_QEMU
>>>
>>>
>>> Thanks, I will adjust the page.
>>>
>>
>> Medium/long term we should consider changing the docs to recommend using
>> qemu-system-arm -M virt, since that's where all the virt improvements are
>> generally going to take place, and it doesn't require an explicit dtb (since
>> it generates ones behind the scene). That will also be the virt machine type
>> used for aarch64, so it will be nice to have parity there.
>
> That certainly sounds the best route. Does that allow the use of
> virtio* for storage/network/display etc?
>

It gives virtio for storage/network automatically, in fact it only supports 
virtio.

virtio display doesn't exist upstream yet. There's work on one but it's a ways 
off AIUI

Though my understanding is that soon people will be looking at adding some 
manner of PCI support to -M virt, which may open the doors for getting 
graphics to work. But I'm pretty ignorant WRT the technical details so I'm not 
really sure.

-M virt also has the best integration for KVM for running on arm hardware, so 
provides some parity there as well.

- Cole