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    VM with GPU passthrough - disabling default framebuffer?

    Scheduled Pinned Locked Moved Compute
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    • W Offline
      woopla
      last edited by

      So after fixing Ryzen Gen1 IOMMU issues (see here), I can pass my GPU to a VM. Problem is, the default framebuffer is still present and is the default graphics (for Linux or Windows).

      My googling shows me there's a gfx_passthru option in Xen that tells Xen to disable the default framebuffer and use the passed-through GPU as the only VGA for the VM. Is there a way to do the same in XCP-NG?

      Thanks,

      Clement

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      • olivierlambertO Offline
        olivierlambert Vates 🪐 Co-Founder CEO
        last edited by

        I have no experience with that. What's your GPU?

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        • W Offline
          woopla
          last edited by

          It's an Nvidia 1070

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          • olivierlambertO Offline
            olivierlambert Vates 🪐 Co-Founder CEO
            last edited by

            With an Nvidia consumer grade GPU, passthrough won't work, because Nvidia driver will refuse to load in a VM.

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            • W Offline
              woopla
              last edited by

              I know it won't work with the Nvidia drivers, but for now I want it to start with the nouveau driver on Linux, and at least get something working.

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              • olivierlambertO Offline
                olivierlambert Vates 🪐 Co-Founder CEO
                last edited by

                It seems someone made it with Nvidia consumer GPU passthrough: he used modded drivers that get rid of the check.

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                • W Offline
                  woopla
                  last edited by

                  I know there are... workarounds 🙂 around that (e.g. for KVM you can hide the fact that it's running inside a VM, and I believe there are similar solutions for Xen).

                  But first things first - I want to get rid of that default framebuffer. Is there a way to pass 'base' Xen config options through XCP-ng (e.g. with an xe command)?

                  MajorTomM 1 Reply Last reply Reply Quote 0
                  • MajorTomM Offline
                    MajorTom @woopla
                    last edited by MajorTom

                    @woopla I'm not sure if this will work in your setup, but I've thought I'll share the solution which worked for me as I tried hard to get rid of bloody framebuffer (which was making the console in XCP-ng Center and in XOA almost unreadable due to tiny or blurred font).

                    After many hours of googling and trying various settings in /etc/default/grub (which theoretically should work, but didn't) I found unix.stackexchange.com/questions/346090/disable-framebuffer-in-qemu-guests.

                    It advised:

                    " disable the framebuffer via a bochs_drm module parameter - i.e. via setting it on the guest kernel command line: bochs_drm.fbdev=off "

                    Precisely, I put into /etc/default/grub the following line:

                    GRUB_CMDLINE_LINUX_DEFAULT="systemd.show_status=1 bochs_drm.fbdev=off"

                    edit: I forgot to mention: the above line is for a VM system, not for XCP-ng host.

                    (The systemd entry is unrelated to fb issue, but I'm quoting it here as a additional tip - I need it to at least partially work around systemd fascist plague).

                    I wonder: will this bochs tip help you?

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                    • W Offline
                      woopla
                      last edited by

                      @MajorTom thanks that could be a solution. In the end I moved my single-machine Homelab to Proxmox, because I have way better control in this specific use-case - I can see IOMMU groupings and figure out which USB controller I can also passthrough. And this works fine, I'm posting this from this VM.

                      XCPng isn't bad, it´s just not suited to my very specific use case.

                      Cheers,

                      Clément

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