[vfio-users] PCI-Stub still needed for now?

[Alex Williamson]

On Sun, Sep 20, 2015 at 8:28 AM, Eddie Yen <missile0407 at gmail.com> wrote:

> Hello, guys, long time no see.
> I have a long time that following updates about VFIO.
>
> As I read AW's blog, I found that there is no pci-stub needed for now.
> Looks like vfio-pci can get video card for 'greedy' graphic driver.
> Is that true?
>

vfio-pci now has an ids option that can be used to claim devices on module
load, much like pci-stub.  Either is a viable option so long as the module
is loaded before host drivers for the GPU.


> Because I'm still using the old method to launch VM with X79 platform.
> (Using pci-stub and QEMU command.)
> But I may got a case that may using IGD as host video output to run KVM.
> May use Z97 or new Z170 as platform.
>
> According to blog, if using the mainstream platform, it's better to use E3
> series.
> Because E3 series had ACS module inside.
> And I know E3 had some models that included IGD.
> So it nay not have IOMMU Group problem? Or it depends on motherboard
> design?
>

No, nowhere do I say that E3 offers any isolation advantage over Core i5 or
i7.  You need to get at least a Xeon E5 to start seeing ACS support on
processor root ports.  Look for reports from other users on Z170/Slylake,
no isolation at the processor or PCH root ports and no quirks to fix it.
Many onboard I/O devices on Z170 are also grouped with system devices.
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