Re: [RFC] XenGT - An Mediated Graphics Passthrough Solution from Intel

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

On Mon, Sep 09, 2013 at 12:46:23PM +0000, Shan, Haitao wrote:
> Hi, Xen Experts,
> 
> This email is aimed at a first time disclosure of project XenGT, which is
> a Graphics virtualization solution based on Xen.
>  
> 
>  
> As you can see, requirements for GPU to be sharable among virtual machines
> have been constantly rising. The targeted usage model might be
> accelerating tasks ranging from gaming, video playback, fancy GUIs,
> high-performance computing (GPU-based). This trend is observed on both
> client and cloud. Efficient GPU virtualization is required to address the
> increasing demands.
>  
> 
> We have developed XenGT - a prototype based on a mediated passthrough
> architecture. We support running a native graphics driver in multiple VMs
> to achieve high performance. A specific mediator owns the scheduling and
> sharing hardware resources among all the virtual machines. By saying
> mediated pass-through, we actually divide graphics resource to two
> categories: performance critical and others. We partition performance
> critical resources for VM's direct access like pass-through, while save
> and restore others.
>  
> 
>  
> XenGT implements the mediator in dom0, called vgt driver. This avoids
> adding complex device knowledge to Xen, and also permits a more flexible
> release model. In the meantime, we want to have a unified architecture to
> mediate all the VMs, including dom0. Thus, We developed a ³deprivileged²
> dom0 mode, which essentially trapped Dom0's access to selected resources
> (graphics resources in XenGT case) and forwarded to vgt driver (which is
> also in Dom0) for processing.

But could be in another domain itself - an device driver domain right?
> 
>  
> Performance critical resources are:
> - Part of the global virtual memory space
> - VM¹s own per-process virtual memory spaces
> - VM¹s own allocated command buffers (actually in graphics memory)
> 
>  
> Others are:
> - MMIO/PIO
> - PCI configuration registers
> - GTT tables
> - Submission of queued GPU commands
> 
> Right now, we support 4 accelerated VMs: Dom0 + 3 HVM DomUs. We've
> conducted verifications based on Ubuntu 12.04 and 13.04. Tests conducted
> in VM include but are not limited to 3D gaming, media playbacks, 2D
> accelerations.
> 
> We believe the architecture itself can be general so that different GPUs
> can all use this mediated passthrough concept. However, we only developed
> codes based on Intel 4th Core Processor with integrated Graphics. Note
> that we don't require VT-d to run our solution.
> 
> If you have interests in trying, you can refer to the attached setup
> guide, which provides step-to-step details on building/configuring/running
> XenGT.
> 
> Source code is made available at github:
> Xen: https://github.com/01org/XenGT-Preview-xen.git
> Linux: https://github.com/01org/XenGT-Preview-kernel.git
> Qemu: https://github.com/01org/XenGT-Preview-qemu.git

Yeey! Awesome! Thank you for sharing that.

> 
> Any comments are welcome!
> 
> 
> Special note: We are making this code available to general public since we
> take community's involvement and feedbacks seriously. However, while we've
> tested our solution with various workloads, the code is only at pre-alpha
> stage. Hangs might happen, so please don't try it on the system that
> hosting critical data for you.
> 
> Shan Haitao
> 


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