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Nvidia vGPU Driver fails to load with error Code 43 on XenServer 7 Hosts with more than 512GB-Ram

30. January 2017

When you try to start a VM with an attached vGPU and the XenServer itself has more than 512GB-Ram it might happen that the driver does not start. You just get an error message with Code 43:
(Sorry for poor quality.)

In some situations it’s even not possible to boot the whole VM:

An emulator required to run this VM failed to start


If you google for the problem you find the following Knowledge-Base-Article from Nvidia.

Unfortunately the information’s in this article only partly worked for us. The first command should automatically add the required parameters to the grub.cfg

Command line: (/opt/xensource/libexec/xen-cmdline –set-dom0 iommu=dom0-passthrough)

Alternatively there is a second method described how to fix it manually:

Or by editing the bootloader (/etc/grub.conf) grub.conf to contain:iommu=Dom0-passthrough

To check the grub.cfg you have to open a console session and browse to one of these folders (depending on the servers boot configuration (BIOS or UEFI Boot)):



Open grub.cfg with vi:
vi grub.cfg

Originally the file looks like this:

Now run the following command:

/opt/xensource/libexec/xen-cmdline –set-dom0 iommu=dom0-passthrough

After that it looks like this:
The iommu parameter is added to module2.

Although it looks like the parameter was added correctly, the error still occurred. I discussed it with Ronald Graß (Citrix Engineer). He thought that the parameter should be added to line multiboot2 (the “xen-line”) and not to module2. Thus I moved it up – the problem was fixed. Later I talked with a XenServer Engineer about it and he confirmed that the multiboot2 line is the correct one. After changing the grub.cfg looked like this:

Later I had a second system with the same problem. So I opened the grub.cfg and added iommu=Dom0-passthrough (the second method from the article). This time it did not work Sad smile. We did many tests and even reinstalled the whole server – the error still occurred. When I compared the working one and the other one – there was only a really tiny difference between the grub.cfg files:


Not working:


As you can see – the only difference was that the parameter in the not working one was with a capital D. So I replaced it with a lowercased d and rebooted the system. Booom – problem fixed. So the parameter is case-sensitive – write everything lower case.

  1. Apologies – I was the article author and the info was provided and verified by the XenServer engineering team. Somehow in the publishing process a capital letter was aquired and should be soon updated

  2. Steve Noel permalink

    Thank you for this, confirmed it’s working for us.

Trackbacks & Pingbacks

  1. Crashing XenServer 7 with Nvidia M60 (and Dell R730) | Jan Hendriks Blog
  2. Workaround for crashing XenServer 7 with Xeon v4 CPUs, Nvidia M60 / M10 (and Dell R730) | Jan Hendriks Blog

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