Oct 302022
 
vGPU nvidia-smi GPU Link Info

If you’re like me, you want to make sure that your environment is as optimized as possible. I recently noticed that my NVIDIA A2 vGPU was reporting the vGPU PCIe Link Speed and Generation that the card was using was below what it was supposed to be running at on my VMware vSphere ESXi host.

I needed to find out if this was being reported incorrectly, if there was an issue, or something else effecting this. In my case, the specific GPU I was using is supposed to support PCIe Gen4, and has a physical connector supporting 4x, my host has PCIe Gen3 slots, so I should at least be getting Gen3 speeds.

NVIDIA A2 vGPU

The Problem

When running the command “nvidia-smi -q”, the GPU was reporting that it was only running at PCIe Gen 1 speeds, as shown below:

        GPU Link Info
            PCIe Generation
                Max                       : 3
                Current                   : 1
                Device Current            : 1
                Device Max                : 4
                Host Max                  : N/A
            Link Width
                Max                       : 16x
                Current                   : 8x

Something else worth noting, is that the card states that it supports a 16x interface, when it actually only physical has a 8x connector. I believe they use this chip on another board that has multiple GPUs on a single board that actually supports 16x.

You could say I was quite puzzled. Why would the card only be running at PCIe Generation 1 speeds? I thought it could be any of the scenarios below:

  • Dynamic mode that alternates when required (possibly for power savings)
  • Hardware issue
  • Hardware Limitation (I’m using this in an older server)
  • Software issues
  • Configuration issue

Unfortunately, when searching the internet, I couldn’t find many references to this metric, however I did find references from other user’s copy/pastes of “nvidia-smi -q” which had the same values (running PCIe Gen1), even with beefier and more high-end cards.

The Solution

After some more searching, I finally came across an NVIDIA technical document titled “Useful nvidia-smi Queries” that states that the current PCIe Generation Link speed “may be reduced when the GPU is not in use”. This confirms that it’s dynamic and adjusts when needed.

Finally, I decided to give some games a shot in a couple of the VMs, and to my surprise when running a game, the “Device Current” and “Current” PCIe Generation changed to PCIe Gen3 (note that my server isn’t capable of PCIe Gen4, which is the cards maximum), as shown below:

        GPU Link Info
            PCIe Generation
                Max                       : 3
                Current                   : 3
                Device Current            : 3
                Device Max                : 4
                Host Max                  : N/A
            Link Width
                Max                       : 16x
                Current                   : 8x

In conclusion, if you notice this in your environment, do not be alarmed as this is completely normal and expected behavior.

Oct 032022
 
NVIDIA A2 vGPU

When deploying automated desktop pools with NVIDIA vGPU on VMware Horizon with an NVIDIA A2 GPU, you may notice provisioning fails with an error.

Error during Provisioning Cloning of VM VM-NAME-01 has failed: Fault type is UNKNOWN_FAULT_FATAL - No GPU capable host available for provisioning VM-NAME-01 with profile nvidia_a2-4q. Please refer to VMware KB 59271 for more details.

Further, when visiting VMware KB 59271 and performing the instructions, provisioning still continues to fail.

Screenshot of error message Automated vGPU Desktop Pool fails to provision due to missing vGPU profiles
Automated vGPU Desktop Pool fails to provision due to missing vGPU profiles

Essentially, at present there is no “supported” to resolve this issue without applying the fix listed in this post. Additionally, if you’re a VMware customer with an active support agreement, I would recommend opening a ticket with VMware Support so that it can be addressed in a future release.

The Problem

The NVIDIA A2 GPU is fairly new, along with VMware vSphere support. Even newer, is the support for vGPU and VMware Horizon, requiring the latest drivers (vGPU Drivers versions 14.2 released August 2022) to enable vGPU profiles for the card.

After troubleshooting this, I noted that the “graphic-profiles.properties” file in “C:\Program Files\VMware\VMware View\Server\broker\conf” did not contain any NVIDIA A2 vGPU Profiles. Additionally, the file available on the VMware KB was also missing these profiles.

The Fix

To fix this, I referenced the NVIDIA vGPU User Guide to note the vGPU profiles allowed on the card, and created my own entries for the configuration file.

After adding these entries, restarting the server (or service), I was able to provision NVIDIA A2 enabled vGPU desktop pools.

To resolve this issue, add the following entries to your “graphic-profiles.properties” file in “C:\Program Files\VMware\VMware View\Server\broker\conf” (note, the contents of the file is case-sensitive):

# NVIDIA A2 Profiles
# Q-Series Virtual GPU Types for NVIDIA A2
nvidia_a2-16q=1
nvidia_a2-8q=2
nvidia_a2-4q=4
nvidia_a2-2q=8
nvidia_a2-1q=16

# B-Series Virtual GPU Types for NVIDIA A2
nvidia_a2-2b=8
nvidia_a2-1b=16

# C-Series Virtual GPU Types for NVIDIA A2
nvidia_a2-16c=1
nvidia_a2-8c=2
nvidia_a2-4c=4

# A-Series Virtual GPU Types for NVIDIA A2
nvidia_a2-16a=1
nvidia_a2-8a=2
nvidia_a2-4a=4
nvidia_a2-2a=8
nvidia_a2-1a=16

After restarting the server or services, you should now be able to use the NVIDIA A2 vGPU profiles with VMware Horizon automated (vGPU) desktop pools.

You should be able to use this fix for other new vGPU cards that have been recently released where the profiles have not been configured for Horizon. VMware is likely to fix this in future released of VMware Horizon.

Sep 042022
 

When either directly passing through a GPU, or attaching an NVIDIA vGPU to a Virtual Machine on VMware ESXi that has more than 16GB of Video Memory, you may run in to a situation where the VM fails to boot with the error “Module ‘DevicePowerOn’ power on failed.”. Special considerations are required when performing GPU or vGPU Passthrough with 16GB+ of video memory.

This issue is specifically caused by memory mapping a GPU or vGPU device that has 16GB of memory or higher, and could involve both the host system (the ESXi host) and/or the Virtual Machine configuration.

In this post, I’ll address the considerations and requirements to passthrough these devices to virtual machines in your environment.

In the order of occurrence, it’s usually VM configuration related, however if the recommendations in the “VM Configuration Considerations” section do not resolve the issue, please proceed to reviewing the “ESXi Host Considerations” section.

Please note that if the issue is host related, other errors may be present, or the device may not even be visible to ESXi.

VM GPU and vGPU Configuration Considerations

First and foremost, all new VMs should be created using the “EFI” Firmware type. EFI provides numerous advantages in device access and memory mapping versus the older style “BIOS” firmware types.

VM Firmware type EFI

To do this, create a new virtual machine, navigate to “VM Options”, expand “Boot Options”, and confirm/change the Firmware to “EFI”. I recommend this for all new VMs, and not only for VMs accessing GPUs or vGPUs with over 16GB of memory. Please note that you shouldn’t change an existing VM, and should do this on a fresh new VM.

With performing GPU or vGPU Passthrough with 16GB+ of video memory, you’ll need to create a couple of entries under “Advanced” settings to properly configure access to these PCIe devices and provide the proper environment for memory mapping. The lack of these settings is specifically what causes the “Module ‘DevicePowerOn’ power on failed.” error.

Under the VM settings, head over to “VM Options”, expand “Advanced” and click on “Edit Configuration”, click on “Add Configuration Params”, and add the following entries:

pciPassthru.use64bitMMIO=”TRUE”
pciPassthru.64bitMMIOSizeGB=32

Example below:

VM GPU and vGPU Memory Settings for 16GB or higher memory mapping

You’ll notice that while our GPU or vGPU profile may have 16GB of memory, we need to double that value, and set it for the “pciPassthru.64bitMMIOSizeGB” variable. If your card or vGPU profile had 32GB, you’d set it to “64”.

Additionally if you were passing through multiple GPUs or vGPU devices, you’d need to factor all the memory being mapped, and double the combined amount.

ESXi GPU and vGPU Host Considerations

On most new and modern servers, the host level doesn’t require any special configuration as they are already designed to pass through such devices to the hypervisor properly. However in some special cases, and/or when using older servers, you may need to modify configuration and settings in the UEFI or BIOS.

If setting the VM Configuration above still results in the same error (or possibly other errors), than you most likely need to make modifications to the ESXi hosts BIOS/UEFI/RBSU to allow the proper memory mapping of the PCIe device, in our case being the GPU.

This is where things get a bit tricky because every server manufacturer has different settings that will need to be configured.

Look for the following settings, or settings with similar terminology:

  • “Memory Mapping Above 4G”
  • “Above 4G Decoding”
  • “PCI Express 64-Bit BAR Support”
  • “64-Bit IOMMU Mapping”

Once you find the correct setting or settings, enable them.

Every vendor could be using different terminology and there may be other settings that need to be configured that I don’t have listed above. In my case, I had to go in to a secret “SERVICE OPTIONS” menu on my HPE Proliant DL360p Gen8, as documented here.

After performing the recommendations in this guide, you should now be able to passthrough devices with over 16GB of memory.

Additional Resources:

Jun 182022
 
Nvidia GRID Logo

When performing a VMware vMotion on a Virtual Machine with an NVIDIA vGPU attached to it, the VM may freeze during migration. Additionally, when performing a vMotion on a VM without a vGPU, the VM does not freeze during migration.

So why is it that adding a vGPU to a VM causes it to become frozen during vMotion? This is referred to as the VM Stun Time.

I’m going to explain why this happens, and what you can do to reduce these STUN times.

VMware vMotion

First, let’s start with traditional vMotion without a vGPU attached.

VMware vMotion with vSphere and ESXi
VMware vMotion with vSphere

vMotion allows us to live migrate a Virtual Machine instance from one ESXi host, to another, with (visibly) no downtime. You’ll notice that I put “visibly” in brackets…

When performing a vMotion, vSphere will migrate the VM’s memory from the source to destination host and create checkpoints. It will then continue to copy memory deltas including changes blocks after the initial copy.

Essentially vMotion copies the memory of the instance, then initiates more copies to copy over the changes after the original transfer was completed, until the point where it’s all copied and the instance is now running on the destination host.

VMware vMotion with vGPU

For some time, we have had the ability to perform a vMotion with a VM that as a GPU attached to it.

VMware vSphere with NVIDIA vGPU
VMware VMs with vGPU

However, in this situation things work slightly different. When performing a vMotion, it’s not only the system RAM memory that needs to be transferred, but the GPU’s memory (VRAM) as well.

Unfortunately the checkpoint/delta transfer technology that’s used with then system RAM isn’t available to transfer the GPU, which means that the VM has to be stunned (frozen) to stop it so that the video RAM can be transferred and then the instance can be initialized on the destination host.

STUN Time

The STUN time is essentially the time it takes to transfer the video RAM (framebuffer) from one host to another.

When researching this, you may find examples of the time it takes to transfer various sizes of VRAM. An example would be from VMware’s documentation “Using vMotion to Migrate vGPU Virtual Machines“:

NVIDIA vGPU Estimated STUN Times
Expected STUN Times for vMotion with vGPU on 10Gig vMotion NIC

However, it will always vary depending on a number of factors. These factors include:

  • vMotion Network Speed
  • vMotion Network Optimization
    • Multi-NIC vMotion to utilize multiple NICs
    • Multi-vmk vMotion to optimize and saturate single NICs
  • Server Load
  • Network Throughput
  • The number of VM’s that are currently being migrated with vMotion

As you can see, there’s a number of things that play in to this. If you have a single 10Gig link for vMotion and you’re migrating many VMs with a vGPU, it’s obviously going to take longer than if you were just migrating a single VM with a vGPU.

Optimizing and Minimizing vGPU STUN Time

There’s a number of things we can look at to minimize the vGPU STUN times. This includes:

  • Upgrading networking throughput with faster NICs
  • Optimizing vMotion (Configure multiple vMotion VMK adapters to saturate a NIC)
  • Configure Multi-NIC vMotion (Utilize multiple physical NICs to increase vMotion throughput)
  • Reduce DRS aggressiveness
  • Migrate fewer VMs at the same time

All of the above can be implemented together, which I would actually recommend.

In short, the faster we migrate the VM, the less the STUN Time will be. Check out my blog post on Optimizing VMware vMotion which includes how to perform the above recommendations.

Hope this helps!