[vfio-users] Switching to Q35

[Zoltán Kővágó]

On 2019-01-01 10:50, Patrick O'Callaghan wrote:
> On Mon, 2018-12-31 at 23:01 +0100, Kővágó Zoltán wrote:
>> On 2018-12-29 16:31, Alex Williamson wrote:
>>> Use virtual machine manager again to create a Q35 VM and re-use your
>>> disk image.  Note that this is the same as moving your disk from one
>>> machine to another with potentially different disk and network
>>> controllers.  If you're using virtio for both, you're probably fine
>>> otherwise you might need to go back to the 440fx machine type and
>>> install extra drivers to make it work.  Also be sure to maintain the
>>> same firmware type in the VM, SeaBIOS or OVMF.  Switching between the
>>> two for an existing VM image is non-trivial.  Thanks,
>>
>> Hi,
>>
>> Reading this thread I decided to try the switch. Since life is too short
>> to figure out libvirt,
> 
> I find VMM easier than working my way through all the Qemu command-line 
> options since I don't understand what most of them are for.
> 
>> I'm running qemu directly, so I just added -M q35
>> and staryed my win8.1 vm and it worked, except, of course, the nvidia
>> driver.
>>
>> Looking at the device manager, on one vm it reverted to the standard vga
>> driver, while on the other it displays my gpu as unknown device without
>> a driver (but it displays the desktop on this unknown device!).
>> If I select update driver, or try to manually reinstall the nvidia
>> driver, I hear that device connected/reconnected sound, the screen turns
>> off, then a few seconds later the vm just reboots.
>>
>> Any idea what is the problem? Did anyone try this configuration? (OVMF +
>> win8.1 x64 + nvidia gtx980 passthrough)
> 
> No idea, but it looks like a different problem from mine.

It looks like the problem is introduced with the commit
b2fc91db84470a78f8e93f5b5f913c17188792c8 which will be part of the next
qemu release. To solve this problem I can either use `-M pc-q35-3.1` or
(probably more preferably) add `-machine kernel_irqchip=on` to the options.

Could anyone who use q35 with win 8.1 and nvidia, download and compile
the latest qemu git and confirm it? (Alternatively using 3.1 you can
specify `-machine kernel_irqchip=split`, it specifies the new default
setting).

Regards,
Zoltan