[vfio-users] vfio, xeon e3s, acs, & gpus -- oh my!

[Joshua Hoblitt]

On 03/31/2017 01:22 PM, Alex Williamson wrote:
>> which does claim ACS support in the overview sheet. Does anyone know if
>> ACS is indeed working with the "pex 8747" and/or the sm x1?sat series of
>> motherboards?  Alternatively, does anyone know of an E3-1200 motherboard
>> that does have working ACS with 2x [8x/16x] PCIe slots?
> The end-to-end topology needs to support ACS, so it really does not
> matter if a switch between the endpoint and the root port supports ACS
> if the upstream root port does not.  Packets could be rerouted at the
> root port regardless of how much isolation exists downstream of it.
Well shoot, I obviously hadn't grasped that. ;(
>> If anyone has followed my rambling this far, thank you for your extreme
>> patience.  I would like to thank Alex Williamson for his vfio blog and
>> the kvmforum talk up on youtube -- I would be completely lost at this
>> point without that information.
> Thanks!  I certainly discourage use of the ACS override patch, which
> at least for my part is why you don't see forward ports of it.  AFAIK,
> it's not possible to get separate IOMMU groups for the processor root
> ports on i3/5/7/E3 otherwise though.  If you need to stick with this
> product family, you'll need to figure out how to make a configuration
> where the processor root ports are used exclusively by either the host
> or the guest.  We do have ACS equivalent isolation in the PCH root
> ports, but of course that moves you further from the CPU and might
> restrict full bandwidth.  Otherwise you need a Xeon E5 or High End
> Desktop processor.  As I document in my setup, I use IGD for host
> graphics and can therefore dedicate the processor root port to the
> guest graphics.  I can use the PCH root ports for a 3rd guest if
> necessary.
I don't believe there is an IGD configuration that would work for me as
I need to drive 3x 1920x1200 displays.  The displays I have (total of 6)
are all DP1.2, which means I need at least least 1 MST capable DP +
another port (DP1.2 doesn't have enough bandwidth for 3 displays at that
resolution).  I had an issue with monitors randomly not going into
powersave when daisy chained via MST and have switched to using 3 fully
independent DPs.

Do you know if all E5s have ACS on the root port -- including the low
end E5-1600v4 family?

Thanks,

-Josh

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