[vfio-users] ACS capabitities for 1366 sockets

[sL1pKn07 SpinFlo]

2016-01-08 1:25 GMT+01:00 Alex Williamson <alex.l.williamson at gmail.com>:
> That's an interesting combination.  This system is old enough that you have
> something more like a traditional North Bridge, South Bridge setup.  Intel
> moved the memory controller to the processor in Nehalem & Westmere, but your
> high speed Root Ports are on the IOH, part of chipset, not the processor.
> These are root ports 00:01.0, 00:02.0, 00:03.0, and 00:07.0.  These root
> ports do have ACS support, so things below them are isolated from one
> another.  Rather than a PCH, you have an IOH.  Those root ports are 00:1c.0,
> 00:1c.2, and 00:1c.4.  Those do not support ACS, do not have quirks, and are
> part of a multifunction device, so they and everything behind them is
> grouped together, that's your IOMMU group 9.
>
> Now, back to your IOH paths, devices 15:00.*  are grouped together because
> they lack ACS between the functions (I believe that Marvell SATA controller
> is one of the ones that uses the wrong requester ID for DMA too).  14:00.0
> is in it's own group.  Then come the PCIe switches.  The downstream ports on
> the switches do not support ACS, so everything downstream of them will be
> grouped together.  This is why group 13 contains not only the GTX 770, but
> also the downstream port at 10:00.0.  That's fine for a GPU assignment use
> case, but would not work well for things like multi-port NICs or SR-IOV
> devices where you want to assign each function to a different VM.  The only
> other interesting one is 08:00.0, where you've got a second layer of PCIe
> switches.  Everything in that hierarchy is already grouped together due to
> the lack of ACS at 06:01.0, making group 21 pretty large.  (I think that
> other Marvell SATA controller also has DMA issues, but it should already
> have quirks in the kernel)
>
> So it looks ok to me.  The isolation isn't perfect, but it's ok for GPU
> assignment.

Very thanks. now is the turn for the cpupin assignment. but is other
history(and this isn't the thread) and I need learn more about it.


Greetigs