Paravirtualization

[Harry Hoffman]

Hi Joy,

Now a days there are primarily two different types of virtualization.

The first is hardware virtualization, where the CPU has extra
instruction sets that allow it to act as a physical CPU to the guest OS
(This is a very simplistic explanation).

In this instance no modification of the guest kernel is required. The
typical example of this is running a windows guest under a linux host.

Another type of virtualization is paravirtualization. This is where the
host OS runs, what is typically called, a hypervisor. The hypervisor
sits in between the hardware and the guest OS and adds additional
instruction sets that help (among other things) the guest OS run more
efficiently.

In this instance your guest OS will come with a modified kernel so that
it can understand the instructions the hypervisor gives it.

If you don't have CPU virtualization then it's very handy to go the
paravirt route.

Hope this helps.

Cheers,
Harry


On Tue, 2010-12-14 at 10:46 +0530, Joy Methew wrote:
> Hello Harry,
>                      thanks for reply.
> will these modification done by user or guest kernel can do this
> automaticaly?
> bcoz i have done lot of time xen peravirtulazation i don`t need to modified
> guest OS.
> 
> 
> 
> 
> 
> On Tue, Dec 14, 2010 at 9:45 AM, <ShivramSubramanian at eaton.com> wrote:
> 
> > Hi Harry,
> >
> > I too am trying to install "guest" operating systems on a Xen modified
> > RHEL5 kernel. But unfortunately it is not happening. It is unable to
> > locate the install media via NFS or HTTP or FTP...Any help would be
> > appreciated.
> >
> > Thanks & Regards,
> > Shivram Subramanian
> > Associate Engineer
> > Software Engineering CoE, EIEC
> > T: +91.20.66 33 7421
> > E: shivramsubramanian at eaton.com
> > J Please consider the environment before printing
> >  -----Original Message-----
> > From: redhat-list-bounces at redhat.com
> > [mailto:redhat-list-bounces at redhat.com] On Behalf Of Harry Hoffman
> > Sent: Monday, December 13, 2010 8:57 PM
> > To: General Red Hat Linux discussion list
> > Cc: redhat-list-request at redhat.com
> > Subject: Re: Paravirtualization
> >
> > Hi Joy,
> >
> > It means that you have a host operating system that acts as a controller
> > for and provides virtual hardware to the "guest" operating systems.
> >
> > In order for the guest operating systems to be able to run they need to
> > have modifications made to their kernel to understand the various
> > instructions that the host gives them via the virtualization software.
> >
> > HTH,
> > Harry
> >
> > On Mon, 2010-12-13 at 19:19 +0530, Joy Methew wrote:
> > > Hello all,
> > >                 anybody can explain me this line for me
> > >                "Paravirtualization requires that the guest operating
> > system
> > > running on the host server be modified so that it recognizes the
> > > virtualization software layer"
> > > Here what is the mean of modified guest operating system.
> > >
> > >
> > > Thanks
> >
> >
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