Hey, >From what I understand in general connecting devices straight to the root >complex is problematic and they should be connected to a bridge. I was kind of >wondering if anybody had any knowledge of this. I find the configuration >really confusing. I still cant really tell how the topology works.
Paige Sent from my iPhone > On Dec 25, 2018, at 5:06 AM, Bronek Kozicki <b...@spamcop.net> wrote: > >> 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 _______________________________________________ vfio-users mailing list vfio-users@redhat.com https://www.redhat.com/mailman/listinfo/vfio-users
