RE: [Xen-users] communication of guest OSes with host system over FC6 with xen

["Petersson, Mats" <Mats.Petersson@xxxxxxx>]

> -----Original Message-----
> From: xen-users-bounces@xxxxxxxxxxxxxxxxxxx 
> [mailto:xen-users-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of anant
> Sent: 06 December 2006 11:25
> To: xen-users@xxxxxxxxxxxxxxxxxxx
> Subject: [Xen-users] communication of guest OSes with host 
> system over FC6 with xen
> 
> 
> Hi 
> i was just wondering about this issue, how does the 
> communication works
> between guest OSes and main dom0 for checking WMI values like 
> win32BIOS, win
> 32  baseport, physical and logical drives etc...over FC6 with 
> XEN as the main host.

Not sure if this is really the question you're asking, but here's my
answer:
1. The BIOS in your system isn't the BIOS used by the Windows guest on
top of Xen - it has a "special" BIOS ("the BIOS" in the text following)
that is supplied as part of the Xen distribution (it's actually part of
the binary called "hvmloader", which is a part of the "startup" of a HVM
guest). 
2. Physical/logical drivers are detected by the BIOS via qemu-dm - see
more about qemu-dm below. The detection is actually done exactly like in
hardware, by sending a command "identify" to the drive - the only
difference is that it's not ACTUALLY going to a real hard-drive (at
least not directly), but to qemu-dm, which responds with size/brand/etc.


Qemu-dm is the "device model", which essentially means that it's the
target of ANY hardware accesses done by the guest. If the guest wants to
read the hard-disk, it goes to qemu-dm. If it wants to read the
keyboard, the guest needs to talk to qemu-dm, etc, etc. There are some
(frequently accessed) hardware elements that reside in the hypervisor
(Xen) itself - the interrupt controller and time-keeping devices, as
this reduces the time it takes to access the "hardware". 

Qemu-dm lives in Dom0 (Linux) will translate a disk-access into a
file-read of a suitable type. Likewise, qemu-dm's "display window" will
be used to display the graphics output from the guest, and any keyboard
activities or mouse-clicks will be transmitted to the guest when
performed within the window. 

I hope this explains what you wanted to know. Please feel free to ask
further questions if you wish. 

--
Mats

> thanks
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> stem-over-FC6-with-xen-tf2767467.html#a7717560
> Sent from the Xen - User mailing list archive at Nabble.com.
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