[vfio-users] How to choose a compatible motherboard?

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If you have a dedicated group for each pci-e device - why would you need
ACS override?

BTW, have you considered trying to build a hybrid(AMD and Nvidia for PhysX)
system or maybe just a quad crossfire one just for the record?
On Oct 23, 2015 1:45 AM, "Nick Sukharev" <nicksukharev at gmail.com> wrote:

> I certainly don't get the login prompt but it displays the GRUB there and
> some text before it switches to my USB video. As long as it doesn't change
> the text mode resolution or do anything with the card other than just text
> output, it seems to work OK with W7 OVFM guest. Somehow it also works
> without the ROM file while printing those messages. In any case, going
> headless only makes sense if you really need it as in my case where I want
> to use all 4 PCIE slots.  I wonder what would ACS give me considering that
> I am already getting separate groups for each of my GPUs + their audio
> component? I considered a Xeon for my setup but the cost was much higher.
>
> On Thu, Oct 22, 2015 at 1:33 PM, Alex Williamson <
> alex.l.williamson at gmail.com> wrote:
>
>> On Thu, Oct 22, 2015 at 2:14 PM, Nick Sukharev <nicksukharev at gmail.com>
>> wrote:
>>
>>> I had this issue with my 1st PCIE slot. Three steps helped:
>>> 1) disabling radeon driver by
>>> creating /etc/modprobe.d/blacklistradeon.conf with a single line
>>> blacklist radeon
>>> 2) specifying GRUB_CMDLINE_LINUX="nomodeset vga=normal video=vesafb:off"
>>> in /etc/default/grub
>>> 3) Using "pure" OVMF.
>>>
>>
>> Don't you still get a VGA mode login prompt on the primary graphics on
>> the host?  That means the host is writing into the VGA space of the device,
>> even while the device is in use by the guest.  Maybe it doesn't cause any
>> noticeable problem since you're using OVMF, but it's still concerning.
>> I've tried this in the past and bumped a keyboard connected to the host
>> while the guest (Linux) was in text mode and got a host login prompt on the
>> guest-owned graphics... very confusing.  I think there's a step missing
>> here about detaching the VGA device from vgacon.
>>
>>
>>> I am pretty sure steps 1 and 3 are also required for secondary slots on
>>> my MB unless I want to use just one non-gpu slot for gpu, then it works
>>> with seabios.
>>> I still get this in dmesg:
>>> vfio-pci 0000:03:00.0: Invalid ROM contents
>>> but no issues because of that.
>>>
>>
>> Linux has special handling for the boot VGA ROM, it's read from the
>> shadow ROM at 0xc0000, which isn't ROM at all and often gets modified by
>> the ROM execution at boot time.  Primary graphics, even if not used for a
>> console, is therefore always more likely to need the ROM passed as a file.
>>
>>
>>> I was trying to make all PCIE slots available for passthrough, if that
>>> is not required some old NVidia in the 1st slot and a radeon in the 2nd (or
>>> vice versa) should be easier. With 1,2,3 I can go completely "headless" in
>>> the sense that I am using USB graphhics on that machine for host.
>>> Also, Haswell i7-5820K works perfectly for x99 socket 2011-3, no need to
>>> go for a Xenon. I doubt you can get 6 core Xenon for a comparable price.
>>>
>>
>> "perfectly" minus not supporting ACS on the processor root ports.  There
>> is still a reason to go for a Xeon.
>>
>
>
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