-------- Original message --------From: Alex Williamson
<[email protected]> Date: 07/10/2020 18:08 (GMT+00:00) To: Steven
Newbury <[email protected]> Cc: Peter Krempa <[email protected]>,
[email protected] Subject: Re: [PATCH] Support x-vga=on for PCI host
passthrough devices On Wed, 07 Oct 2020 14:20:21 +0100Steven Newbury
<[email protected]> wrote:> On Wed, 2020-10-07 at 15:07 +0200, Peter Krempa
wrote:> > On Wed, Oct 07, 2020 at 13:59:35 +0100, Steven Newbury wrote: > > >
When using a passthrough GPU with libvirt there is no option to> > > pass
"x-vga=on" to the device specification. This means legacy > > > > Please note
that we don't add support for experimental qemu features> > (prefixed with
"x-") until they are deemed stable and the x- is> > removed, so this patch
can't be accepted in this form.> > > Okay, so should I bug qemu to promote
the feature to stable? It's been> like that forever, it's certainly not a new
feature:> >
https://github.com/qemu/qemu/commit/f15689c7e4422d5453ae45628df5b83a53e518ed> >
So it's been that way for 8 years!It's that way upstream because VGA routing is
a nightmare, it'sessentially broken on any system with Intel graphics because
the devicealways has VGA regions routed to itself. That problem is not
gettingbetter, but the demand for VGA is getting less, so there's very
littleincentive to work on the problem rather than just letting it die outonce
nobody cares about VGA. Any 600 series or newer GeForce cardshould have a UEFI
ROM available. Also note that VGA support can beconfigured both as a module
option of vfio-pci and a build option, sothere's no guarantee that a display
class device will have the VGAregions available for QEMU to use this option.
Thanks,I'm still going to fix up my patch even if it's not going to get
committed. It's very useful for me, my old nvidia card doesn't work without
it, and I also need it for seabios/dos compatibility with my ATIs. In fairness,
I haven't tried it with my Intel, it's too old to support the new vGPU stuff
and I need to see what I'm typing! ;-)For what it's worth, I had no trouble
with GPU passthrough once I realised it needed x-vga=on. VGA arbitration was
automatically switched. It's been rock solid stability wise, although the 8800
has horrible VGA/DOS performance. Windows10 runs like on bare metal.
