VMworld session DV2363 – CVP Tech Deep Dive « VM Junkie
CVP is a powerful client hypervisor solution, which is part of the greater VMware View offering. It is not going to be offered standalone, it is a View product only. It helps create what the presenters called a “thin” thick client.
There are two approaches to doing a client hypervisor: Direct Assignment or Advanced Device Emulation.
In Direct Assignment, technologies like Intel VT-D or other software techniques are used to pass through a physical device (such as a video card) directly into the VM. This has some advantages such as lower overhead, and if you’re running Windows in your VM then all you need is a set of Windows drivers, which are easy to find. Passthrough is also much easier to program…
It has several downsides, however. For example, it ties your VM to that particular hardware which reduces portability. It also becomes difficult to interpose on that device. For example, if the video card is owned by the VM, there’s no way for the hypervisor to access it. Same goes for the network card. The point being – if all you’re doing is passing through your physical devices, why do you need a Client Hypervisor? Just run native. You can’t add value when using passthrough on everything. For some device types (such as USB) where the O/S is expecting hardware to appear and disappear, passthrough is okay
1 comment:
I couldn't agree more, Stephen. I have been working on a client hypervisor technology for the last year and a half, and our approach has been to avoid pass-through to maintain VM portability at all costs. This makes maintaining a high performance user experience more difficult, but it is not impossible. As you say, there are some legitimate use cases for pass-through, but I am amazed at how many people are out there touting hypervisors where the "best" feature is the ability to bypass the hypervisor. :)
Doug Lane
Virtual Computer, Inc.
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