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Re: [Xen-users] x86 hw virtualization

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Subject: Re: [Xen-users] x86 hw virtualization
From: Mark Williamson <mark.williamson@xxxxxxxxxxxx>
Date: Wed, 22 Jun 2005 16:39:39 +0100
Cc: Thomas Lohmüller <thomas@xxxxxxxxxxxxx>
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> I have to buy a new SOHO-server soon. Please let me ask some xen-related
> questions here...
> Is the hardware needed for x86 hw virtualization already available and what
> are the advantages of using hw virtualization?

The advantage is that it makes it simpler and more efficient to implement 
*full* virtualisation than using purely software techniques.

For Xen's paravirt API there's currently no performance benefits to using HW 
with virtualisation assistance.  i.e. if you want to run Linux, NetBSD, 
FreeBSD it'll probably be faster to run the native Xen port than to use HW 
assisted virtualisation.

In 3.0 there won't be any advantage to having HW assists unless you want to 
run unmodified guests (e.g. to consolidate a load of legacy software stacks 
on one system).

> It looks like Pentium D (8x0) does support virtualization. Is
> chipset-support also required?

My understanding was that VT will work with existing chipsets. (anybody - am I 
right?).  If it does, I guess I might have to buy one myself!

> Is someone already using such hardware?

Well, some Xen developers are ;-)

Basically, Intel has had VT SDVs (Software Development Vehicles) for quite a 
while now.  I imagine other major virtualisation players also have access to 
them.  They're not publically available yet.

> According to the roadmap XEN 3 will be released in the next few weeks. Will
> it fully support hw virtualization?

It'll support it and be able to boot (at least some) unmodified guests.  
Linux, BSD, etc are known to boot.

> And (much more interessting) will it allow unmodified guests (Windows)?

I'm not sure what the plan is but I suspect that it initially won't.  Running 
Windows is relatively difficult - it uses loads of weird features of x86.  
Windows support will *definitely* eventually be supported on machines with HW 


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