I was just reading the XenFAQ.
In here is stated:
7.3. In DomU, how can I use
3D graphics.
In a para-virtualized domain, you could give access to the
graphics card by hiding the device from Dom0 and giving the DomU of choice
access to this card. [Sorry, I don't know more details than this - maybe someone
else can fill in more here. --Mats Petersson] The frequently asked question
comes from people who want to use Windows in a HVM domain to play games or run
high-end 3D graphics applications, and the answer here is "Not yet". The problem
here is that the OS isn't loaded directly at address zero when it is a guest-OS
(DomU), so we're lying to the OS about it's location (because most OS's don't
quite understand the concept of memory that doesn't actually start at address
zero). So, the OS thinks that it's been loaded at an address of, say, 0..256MB,
but in reality it's been loaded at 256MB..512MB. When it then talks to the
graphics cards, it will give the graphics card a physical address of somewhere
between 0..256MB, which of course doesn't work for the graphics card - as it
should really be reading somewhere between 256MB..512MB. So what can we do about
it? There are a number of different solutions that could work: 1. Rewrite the
graphics driver so that it understands Xen. Possible, but hard work, even if you
have easy access to the source-code. Most graphics chip manufacturers do not
have open-source drivers. 2. Use some alternative way to access the desktop,
such as Remote Desktop. This doesn't necessarily work for real high-end apps or
games, but it's probably better than the graphics card emulation in HVM. 3. Wait
for hardware and software to support IOMMU. An IOMMU is a device that will
support mapping memory addresses for a domian to some different address when
that domain's hardware is being used. There is currently (high-end) server
hardware that support this, but no desktop machines. Expect this to change in
the future, but not very soon.
I was thinking, if the memory address being incorrect between the DomU and the actual video card is the issue here, can we:
Install Dom0 on the address range of 1024MB-1536MB, and then configure it to install the 'gaming' domU on the range of 0-512MB, thereby making the memory addresses correct for the IO's needed to run the 3D application?
Is this feasible?
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