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Xen - VGA passthrough is the way to go!!!

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  • #71
    if i have only one monitor and 1 display card, can i perform VGA passthrough?

    besides, is it "stable"? e.g will it works on nvidia 690, but fail on nvidia 680
    or works on HSI cards, but fail on Inno3D cards.

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    • #72
      Originally posted by unknown2 View Post
      if i have only one monitor and 1 display card, can i perform VGA passthrough?
      No, you need 2 display cards (eg. a built-in one on the motherboard and a discrete PCI-E graphics card or a laptop with something like an Optimus setup with 2 GPUs)

      What I want to know is if it's possible for Windows to have accelerated graphics display on an output with no 3d acceleration. Eg. for a physical machine, you might have one of those USB GPUs with a second display on it, would it be possible to display part or all of a game window on that output, with the 3D work being done by a PCIE GPU and redirected back via the PCIE bus to the other output, even if it's a significant performance hit.

      If that's possible, then you could have Xen pass through a discrete GPU, and also emulate the usual Cirrus graphics. The guest sees 2 heads, but you only really work on the Cirrus display with the discrete GPU doing 3d work and passing it back to the emulated display. Basically you could have a hardware-accelerated guest display in a window on the Dom0 desktop without having to dedicate a monitor (or monitor input) to it.

      Like I said, it'd likely cause a big performance hit, but if it's less than 50% it'd probably be acceptable for a lot of cases.

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      • #73
        I have a friend taht has been running this setup for quite awhile with older nvidia drivers I've seen it as well. In fact im have his old geforce 8800gtx 320Mb in my box right now > .

        The lastest Nvidia drivers don't work... they ripped out support for it.

        AMD is pretty much the way forward for this technology.

        Dunno if the open source drivers work.. they ought to but who knows.

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        • #74
          Originally posted by grantek View Post
          No, you need 2 display cards (eg. a built-in one on the motherboard and a discrete PCI-E graphics card or a laptop with something like an Optimus setup with 2 GPUs)

          What I want to know is if it's possible for Windows to have accelerated graphics display on an output with no 3d acceleration. Eg. for a physical machine, you might have one of those USB GPUs with a second display on it, would it be possible to display part or all of a game window on that output, with the 3D work being done by a PCIE GPU and redirected back via the PCIE bus to the other output, even if it's a significant performance hit.

          If that's possible, then you could have Xen pass through a discrete GPU, and also emulate the usual Cirrus graphics. The guest sees 2 heads, but you only really work on the Cirrus display with the discrete GPU doing 3d work and passing it back to the emulated display. Basically you could have a hardware-accelerated guest display in a window on the Dom0 desktop without having to dedicate a monitor (or monitor input) to it.

          Like I said, it'd likely cause a big performance hit, but if it's less than 50% it'd probably be acceptable for a lot of cases.
          i have 1 intel SandyBridge CPU (on-chip graphic) + AMD display card, then i can use the intel GPU for normal Linux work and dedicate the GPU to windows, right?

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          • #75
            Does this work for pci-e GPUs too?
            If yes: What do I have to change in the config?

            EDIT: Do I need something special to use pciback?
            Get the following error when using the xen_remove.sh:
            xen_remove.sh: 7: xen_remove.sh: cannot create /sys/bus/pci/drivers/pciback/new_slot: Directory nonexistent
            xen_remove.sh: 9: xen_remove.sh: cannot create /sys/bus/pci/drivers/pciback/bind: Directory nonexistent

            Seems I'm missing pciback, how could this happen?
            modprobe pciback
            FATAL: Module pciback not found.

            Kernel is Xen 4.1
            Last edited by thorgas; 08-16-2012, 12:33 PM.

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            • #76
              modprobe xen-pciback did the trick
              now I'm getting:
              Code:
              Error: pci: improper device assignment specified: pci: 0000:01:00.1 must be co-assigned to the same guest with 0000:01:00.0, but it is not owned by pciback or pci-stub.
              EDIT:
              #radeon 7950
              remove_device "0000:01:00.0"
              remove_device "0000:01:00.1"

              together with
              pci=['01:00.0','01:00.1']

              did the job but now there is:
              Error: Device model isn't ready for commands

              This error seems to have to do with LVM...
              Last edited by thorgas; 08-16-2012, 01:04 PM.

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              • #77
                Originally posted by jockinator View Post
                vif = [ 'type=ioemu, bridge=br0' ]
                disk = ['phy:/dev/sda7,ioemu:hda,w','phy:/dev/sda9,ioemu:hdb,w']
                acpi = 1
                boot="c"
                sdl=0
                serial='pty'
                Jockinator, how did you set up sda in general and specifically sda7?

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                • #78
                  The following error didn't have anything to do with LVM or my virtual hard drive:
                  Code:
                  Error: Device model isn't ready for commands
                  Looking into the logs I found out that qemu is missing a file so I did the following:
                  Code:
                  ln -s /usr/share/qemu-linaro/keymaps/en-us /usr/share/qemu/keymaps/en-us
                  everything running now, tutorial wil follow soon

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                  • #79
                    Now I hopefully can give something back to you, the ones supporting me very good.

                    My Tutorial for PCI Passthrough: http://gro.solexiv.de/2012/08/pci-passthrough-howto/

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                    • #80
                      Thanks!

                      Looks like a good intro to Xen, I'd just like to note that this is "native Xen", using their xm tool. Xen SHOULD also support creation and management of machines via libvirt, but last time I used libvirt with Xen it didn't present me with all of the features I needed, I assume this is the same with VGA passthrough.

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