[vfio-users] (good) working GPU for passthrough?

[Alex Williamson]

On Mon, 11 Feb 2019 22:06:36 +0100
Tobias Geiger <tobias.geiger at vido.info> wrote:

> > On Thu, Jan 17, 2019 at 11:03:03PM +0100, Tobias Geiger wrote:  
> >> Hello!
> >>
> >> after nearly 5 years of passing through my Radeon HD7800 - it feels old and
> >> slow when used with newer games and 1GB of RAM also doesn't feel right
> >> anymore...
> >>
> >> I tried a VEGA 64 - i was able to live with the ACS patch needed here (Z170
> >> Chipset... not needed with the old HD7800, but whatever...) - but i couldn't
> >> stand the reset/FLR/Bug which forces you at least to suspend/resume the host
> >> when you want to reboot only the guest...
> >>
> >> So my question is - AMD or NVIDIA, i dont care, cheap or superexpensive (ok,
> >> not the quadros) - what do you recommend these days for a hassle-free
> >> passthrough experienence (well at least mostly - acs patch needed would be
> >> ok, reset bug not so... it just makes it unhandy to use in day-to-day
> >> scenarios...)  
> > Wouldn't needing the ACS patch depend on your mobo as opposed to your GPU?  
> 
> 
> I thought so, too! But then this: For my old HD7850 i do NOT need ACS 
> patch, to get it working flawlessly in my Z170 Board - it works with a 
> debian standard kernel even;
> 
> The Vega 64 - in the same slot, same board - needs the ACS patch...
> 
> dont ask me why... i can only guess it might have to do with the pci 
> bridges "within" the Vega64... but thats not more than a very uneducated 
> guess....

Generally the ACS patch should only depend on the motherboard unless
you're trying to split the individual functions of a card to separate
VMs.  It shouldn't make much difference whether those functions are
separate devices downstream of an on-card switch or functions within a
multi-function device when assigned to a single VM.  The motherboard
ACS override would control things like whether separate physical slots
are grouped together.  We can only speculate without more data though.
Thanks,

Alex