Virtualization

[Maximilian]

How does it work from a software perspective?

For example a virtual graphics card, im just gonna have a guess at how it operates, tell me how far off i am :whiste: A virtual graphics card is a software object of some sort and takes calls from the guest OS which it translates into calls that the host OS can understand which the host OS then acts on. Is that remotely close to what happens?

Ive been learning about separating the UI from the core system in Java and how "controller objects" help with this by translating method calls from the UI into method calls to the core system to get what the UI wants and it clicked in my head oh maybe that's how virtualization works

 

[hamunaptra]

yeah pretty much, using virtualbox as an example. When you install a guest OS , after the install you install "guest additions / extensions" that are drivers that allow the guest OS to gain more direct access to the hardware by allowing the extension drivers to make calls to the host OS on behalf of the guest OS virtualized 'hardware'.
So, in this case the extension drivers function as the objects I think you are referring to =)

 

[Maximilian]

Ah cool, its good to have an idea of how these things work

 

[hamunaptra]

If ya want a deeper understanding how it works w/ hyper-v .. I recommend reading the hypber-v sections in windows internals books... Very comprehensive coverage how it all works =)

 

[Nothinman]

How does it work from a software perspective?

For example a virtual graphics card, im just gonna have a guess at how it operates, tell me how far off i am :whiste: A virtual graphics card is a software object of some sort and takes calls from the guest OS which it translates into calls that the host OS can understand which the host OS then acts on. Is that remotely close to what happens?

Ive been learning about separating the UI from the core system in Java and how "controller objects" help with this by translating method calls from the UI into method calls to the core system to get what the UI wants and it clicked in my head oh maybe that's how virtualization works

At a very high level, yes. I believe what you're describing is what VMware calls binary translation which was their original primary method of virtualization. Whatever instructions can be passed directly the the CPU without modification are done as quickly as possible, ring 0 instructions that may affect the host OS are modified in some way to prevent that or executed in software for the VM.

Now that's changed a good bit because the virtualization features built into modern CPUs remove a lot of the need for the translation or assists with making it faster and more seamless.

 

[zanejohnson]

also think of having multiple virtual servers, within 1 box....

fileserver: running 2k3 server
dns/dhcp server: running on another virtual os flavor of your choice
exchange server, on another stand alone virtual os

all on the same hardware, running under a "host os" (Vmware or HyperV)