On Tue, 25 Dec 2018, at 12:57 PM, Paige Thompson wrote: > Hi, > > As you probably know there is a workaround to use i440fx instead of q35 > to get the R9 390 working with VFIO. However, I have managed to get it > working with Q35 by adding a PCIe bridge as well as upstream and > downstream ports to the configuration. You've probably noticed that the > R9 390 card works fine with Q35 up until the point in which you install > the AMD drivers and then it starts crashing. As near as I can tell the > driver simply doesn't like it if you attach the video card directly to > the root complex. > > Here is a link to the configuration that I am using: > https://gitlab.com/snippets/1788426#note_127191397 > qemu command-line rough translation: > https://gitlab.com/snippets/1788426#note_127194064 > For the entire work log : https://gitlab.com/snippets/1788426 > > I'd also like to point out that this also works with a Linux guest as I > confirmed a moment ago. I never could get Linux to work with either > i440fx or q35 before I tried using a pcie bridge in q35. My > understanding of why Windows would work with i440fx is unclear but I > know that pcie devices essentially speak the same as pci devices and > there are no pcie devices on i440fx platforms; still whatever the amd > drivers check for is somehow circumvented in that particular > configuration. > > I'm surprised nobody knew to suggest this, I sort of figured this out > based on something I read somewhere about how it's a bad idea to allow > devices to talk directly as discrete devices to the root complex anyway. > So, I gave this a try and low and behold it worked. It won't give you > any performance improvements, but q35 is a more accurate emulation of a > modern system and may help with other aspects of troubleshooting, it > just requires more topology complexity to be configured correctly. > > Hope that helps,
HI Paige thanks for sharing, this is interesting. FWIW I am currently using Ubuntu Bionic with vfio GPU passthrough but I have given up on AMD cards years ago and am using nVidia Quadro now, which does not have problems with 440FX. B. -- Bronek Kozicki b...@spamcop.net _______________________________________________ vfio-users mailing list vfio-users@redhat.com https://www.redhat.com/mailman/listinfo/vfio-users
