Re: [Qemu-devel] selecting VIRTIO_INPUT and VIRTIO_VGA

[Laszlo Ersek <lersek@redhat.com>]

On 07/21/15 14:08, Alexander Graf wrote:
> On 07/20/15 21:06, Laszlo Ersek wrote:
>> Cc'ing Alex
>>
>> On 07/13/15 12:15, Paolo Bonzini wrote:
>>>
>>> On 13/07/2015 09:32, Gerd Hoffmann wrote:
>>>>> and virtio-vga is only compiled on 64-bit Intel?
>>>> There is virtio-gpu-pci ...
>>>>
>>>> Any specific reason why we need vga compatibility on !x86?
>>> I was actually thinking about 32-bit x86. :)  I agree that !x86 is not
>>> necessary.
>> I disagree :)
>>
>> (This is actually my more important followup to this thread; the other
>> message I just couldn't resist sending.)
>>
>> Gerd recently contributed virtio-vga support to OvmfPkg/QemuVideoDxe:
>>
>> https://github.com/tianocore/edk2/commit/94210dc9
>>
>> That support depends on vga compat. All fine.
>>
>> What's probably not obvious is that I had ported
>> PcAtChipsetPkg/PciHostBridgeDxe to ArmVirtPkg -- which drives Alex's
>> generic PCIe host bridge, exposed on qemu-system-(arm|aarch64) -M virt
>> -- and included OvmfPkg/QemuVideoDxe in the ArmVirtQemu.dsc build too.
>>
>> That means you can currently stick a -device VGA into -M virt, and it
>> will work. Since OvmfPkg/QemuVideoDxe recognizes virtio-vga (see edk2
> 
> For some definition of work, yes :). It will work perfectly fine with
> TCG, you will run into cache coherency problems with KVM because the
> guest maps MMIO regions (like the vram) as uncached while QEMU accesses
> it as cached.

Yes, I'm aware, I just didn't want to drag that thread into this
discusson as well ;)

> 
>> 94210dc9 again), and the driver is included by ArmVirtQemu.dsc, I think
>> it would be probably useful to build the device model for arm/aarch64
>> targets too.
>>
>> See also QEMU commit 332261de2b (together with its parent commits).
> 
> I agree. Also, as far as I understood Marc, his hope was that the fix to
> halfway working VGA emulation would be virtio-gpu.

Not sure how (if!) we're going to be able to drive that from the
firmware! :)

Thanks
Laszlo