Re: [Qemu-devel] VFIO VGA passthrough

[ching]

On 11/20/2012 11:27 PM, Alex Williamson wrote:
>
> Getting VGA to work in a guest is mostly black magic and luck at this
> point.  The warning you're getting isn't preventing anything.  We use
> device reset to try to clear the state of the hardware between runs.  If
> it's not available we can potentially leak data through the device and
> may see issues with reproducibility since we can't return the device to
> a known state.
>
> The assigned VGA device should not be used for anything on the host,
> which it seems like you've taken care of.  The host shouldn't even have
> a blinking cursor on the display.
>
> It's been reported that "-cpu host" helps, but that's possibly very
> similar to what you specify below.  When I tested secondary VGA with an
> ATI card I used "-vga std" and I made the devices appear as
> multifunction in the guest, ex:
>
> -device vfio-pci,host=1:00.0,multifunction=on,addr=4.0 \
> -device vfio-pci,host=1:00.1,addr=4.1
>
> I also first booted without the AMD Catalyst driver installed.  The
> assigned devices are unused, but the guest still boots.  Then installed
> the Catalyst driver, after which rebooting causes the std VGA to go
> blank after an initial startup screen and Windows uses the assigned
> device exclusively.  Good luck, there's obviously still work to do in
> this space.  Thanks,
>
> Alex
>
>
>
>

i am new in pci passthrough has a few more question:

1. is your vga card a PCI Express card?
2. there is a pci bridge in the same iommu group, do i need to pass to the 
guest?

    00:01.0 PCI bridge: Intel Corporation Xeon E3-1200/2nd Generation Core 
Processor Family PCI Express Root Port (rev 09)

3. do i need to dump the vga bios and pass it to guest?

Thanks in advance

ching