Re: [Xen-devel] Xen as a kernel module

[Mark Williamson <Mark.Williamson@xxxxxxxxxxxx>]

> > Right now Xen is mapped somewhere in top of memory, I am not sure how
> > domains are kept out of there, but I suppose it has to do with segments.
>
> As I understand this xen runs in ring0 and pushes the guests kernels one
> ring up into ring1 and then uses traps to allow the guest OSes to trap into
> the hypervisor as necessary.

Yup.  Xen is mapped into the top 64MB of virtual address space of every 
process (just above the Linux kernel).  Segmentation is indeed used to ensure 
that:
* user processes can only see their own memory
* guest kernels can see their own memory and user process memory
* Xen can see guest kernel memory and user process memory within the guest

This is a straightforward extension of the way segments are used in vanilla 
Linux on x86.

Cheers,
Mark


-------------------------------------------------------
This SF.Net email is sponsored by: IntelliVIEW -- Interactive Reporting
Tool for open source databases. Create drag-&-drop reports. Save time
by over 75%! Publish reports on the web. Export to DOC, XLS, RTF, etc.
Download a FREE copy at http://www.intelliview.com/go/osdn_nl
_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxxxx
https://lists.sourceforge.net/lists/listinfo/xen-devel