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

[Alex Williamson]

On Sun, Sep 20, 2015 at 8:51 AM, Blank Field <ihatethisfield at gmail.com>
wrote:

> It is possible to bind needed devices to vfio-pci on the kernel command
> line now.
> Alex himself, afair, uses e3-1245v3, it has IGD and the ACS is almost fine
> there.
>

Argh, please read carefully, I describe how E3 does not have isolation on
the processor root ports, but it works for my configuration.


> Usually only processor root ports have ACS and isolation between devices,
> so they get grouped into separate groups.
>

No, i5, I7, and E3 do NOT have ACS on the processor root ports.  Everything
plugged into processor root ports will be grouped together.


> If there is no isolation between devices, they end up in one group: you
> must patch your kernel and hope it helps or bind every device to vfio-pci.
> The problem is - we don't know if the new motherboard+chipset+cpu provides
> the needed isolation, it is only guaranteed on E5 series of CPUs, which are
> expensive as hell.
>

E5-1600 series is fairly competitive.


> Intel graphics don't like multiple vga arbitration participants: you can
> work around this by the following methods:
> 1. Patch i915 driver.
> 2. Use OVMF and disable vga on the discrete card via vfio-pci module
> option.
> 3. Use full UEFI on the host and make i915 forget about VGA and it's
> arbitration.
>

Do we really know that i915 doesn't use VGA regions on a UEFI host?  I'm
not sure that's true.
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