[vfio-users] Checking for EFI and general questions

[Felix Mayr]

> So there are devices which are
> grouped in IOMMU groups, I can only passthrough a whole group. This can
> cause problems if there is a group where I want to passthrough one but not
> all devices. A way to fix this is a patched kernel like this
> https://aur.archlinux.org/packages/linux-vfio/. This is no problem for
> Haswell-E. Correct?

Afaik this seems true, the processor ports are isolated with Haswell-E.

> Other than that, thanks for the explanations and links (yes, I am German
> :-) ), I think I understand a bit more now. What I don't understand, why
> can I use the nvidia 210 only with Haswell-E?

First off basically you want your GPUs directly connected to the CPU for 
best performance and not over the chipset which only has the equivalent 
of 4 PCIe-Lanes shared for everything you usually connect things to 
(USB, Sound, PCI, small PCIex1s). Secondly most Xeon E3/Core i have 
integrated graphics which are a) more powerful than a Geforce 210 and b) 
sport really good (libre) graphics drivers.
Adding to the first point the difference between Intels small sockets 
(11xx) and big sockets (2011) ist the number of available PCIe-Lanes.
The first only has 16 PCIe-Lanes from the CPU which are split in up to 3 
slots (and this only with higher end boards) and all other periphery/the 
chipset uses DMI for CPU-connection (4 PCIe-Lanes equivalent). PCIe-ACS 
ist not supported on the CPU port, where you put your GPU and the 
chipset is basically a field of quirks and luck I think (as an enduser) 
[and since you only have 4PCIe-Lanes (16GBit/s if I remember correctly) 
for all your periphery you don't really want to put your GPU there].
The second has 28 to 40 Lanes from the CPU which are supported with ACS, 
so that the different physical slots get into separate IOMMU-groups and 
you can arbitrarily choose which addin-card you want to passtrough to 
the VM. For the chipset (onboard Sound, USB, SATA) the same things hold 
true as for the small platform.

I personally use a MSI B85M-G43 with an Intel Xeon E3-1245v3, running 
the host on IGP and passing an UEFI-enabled Radeon R9 390 into the Win 
10 VM. The OS is Debian Jessie which imho means it should run on every 
current Linux distribution.