Linux Virtualization - Feb 2009 - Device Drivers in xen, looking also for a white book about how xen works exactly

Hello,

 

I'm reading an excellent documentation about virtualisation in embedded
system.

 (available on open kernel labs site)

 

I have read these things : (It talks about managing drivers in a virtualization
system)

 

"A straight virtualization approach can accomodate this by running the
device the device driver inside the VMM. This requires porting all drivers to
the hypervisor environnement , with no reuse of guest os driver"

 

A much better approach is to share a single driver between multiple vms, without
including it in the hypervisor. This requires that ecah participating subsytem
has a device modem for which it has a device driver. Typically, the real device
driver is contained in one of the participating system, but a better  (safer)
solution is to separate it out into in own subsystem"

 

I want to know how it works on xen.

I think that :

 

 All drivers are in the hypervisor, when a guest requires to use a device, 
guest uses drivers which has been rewriten for xen in order to contact the
hypervisor. Then, the hypervisor which has all real drivers (not modified) call
the real device ?

 

or that :

The real device driver is contained in the dom0 system, the dom0 manage driver
for all domU.

 

I have three questions :

 

1 -  Which is the good scenario ? (if one is good ) :o)

2 - If drivers for guests are rewritten to call hypervisor or dom0 instead of
the device directly, who devellops driver ?

(xen devellopers ? or developper for kernel mainline)

3- Which is the real utility of dom0 system ? (just I/O and administration of
virtual machines)

 

Last question, is someone have find a good white paper or doc which explains how
xen works ?

(and where i can find probably answers for my questions ??)

 

Thanks for all this details.

Best regards

 

Patrick Archibal

 

 

 

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Patrick

Consider reading this:

http://www.amazon.com/Definitive-Hypervisor-Prentice-Software-Development/dp/013234971X/ref=pd_sim_b_1

To your questions:

1. Real device drivers run in dom0.
Dom0 also runs the backend drivers that support the guest drivers in
paravirtualized domUs, and runs the emulation of virtual devices
presented to HVM domUs.

2. Guest drivers are largely written by the xen community for
paravirtualized ports of guest OSes.

3. Dom0 currently provides real device drivers and infrastucture to
support running both PV and HVM guest domUs.

Again, please consider reading that book.

Christopher

On Sat, Feb 28, 2009 at 12:54 PM, Patrick Archibal <bugpb60 at
hotmail.com> wrote:
> Hello,
>
> I'm reading an excellent documentation about virtualisation in embedded
> system.
>  (available on open kernel labs site)
>
> I have read these things : (It talks about managing drivers in a
> virtualization system)
>
> "A straight virtualization approach can accomodate this by running the
> device the device driver inside the VMM. This requires porting all drivers
> to the hypervisor environnement , with no reuse of guest os driver"
>
> A much better approach is to share a single driver between multiple vms,
> without including it in the hypervisor. This requires that ecah
> participating subsytem has a device modem for which it has a device driver.
> Typically, the real device driver is contained in one of the participating
> system, but a better  (safer) solution is to separate it out into in own
> subsystem"
>
> I want to know how it works on xen.
> I think that :
>
>  All drivers are in the hypervisor, when a guest requires to use a
> device,  guest uses drivers which has been rewriten for xen in order to
> contact the hypervisor. Then, the hypervisor which has all real drivers
(not
> modified) call the real device ?
>
> or that :
> The real device driver is contained in the dom0 system, the dom0 manage
> driver for all domU.
>
> I have three questions :
>
> 1 -  Which is the good scenario ? (if one is good ) :o)
> 2 - If drivers for guests are rewritten to call hypervisor or dom0 instead
> of the device directly, who devellops driver ?
> (xen devellopers ? or developper for kernel mainline)
> 3- Which is the real utility of dom0 system ? (just I/O and administration
> of virtual machines)
>
> Last question, is someone have find a good white paper or doc which
explains
> how xen works ?
> (and where i can find probably answers for my questions ??)
>
> Thanks for all this details.
> Best regards
>
> Patrick Archibal
>
>
>
>
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