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Re: [Xen-devel] how hypervisor separates assembly instructions

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Subject: Re: [Xen-devel] how hypervisor separates assembly instructions
From: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Date: Fri, 14 Oct 2011 16:52:45 +0100
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On 14/10/11 16:43, Tapas Mishra wrote:
> As far as my understanding goes a CPU gets Assembly instructions to work

The CPU reads computer opcode from memory.  (Assembly instructions are
the name for the mnemonics, not the binary representation which the CPU
actually runs)

>  and
> upon those instructions it works. These assembly instructions come
> from the OS running on top of bare metal.

Not really.  All programs are just opcode which the CPU can run.  OS's
are the same as regular programs in this regard.

> I have some understanding of hypercalls.
> So what does a hypercall implement that it is able to separate the
> different Assembly instructions
> coming from different Guest OSeS or in other words how does the
> hypervisor separates the Assembly instructions which should be run for
> different Guest OSeS running on top of hypervisor.I want to know it
> technically not theoretically.

The hypervisor "separates" different operating systems in the same way
that regular operating systems separate different processes.

> --
> ------------------------------
>
> Tapas
>
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-- 
Andrew Cooper - Dom0 Kernel Engineer, Citrix XenServer
T: +44 (0)1223 225 900, http://www.citrix.com


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