Re: [Xen-devel] [PATCH 00/13] Nested Virtualization: Overview

[Bruce Edge <bruce.edge@xxxxxxxxx>]

On Fri, Nov 12, 2010 at 10:39 AM, Christoph Egger <Christoph.Egger@xxxxxxx> wrote:

Hi!

This patch series brings Nested Virtualization to Xen.
This is the sixth patch series. Improvements to the
previous patch submission:

- Move GIF definition into SVM
- Move VMEXIT emulation into SVM
- Introduce hooks for getting host/guest cr3 for use with hap-on-hap
  per proposal from Eddie Dong
- Moved fields from struct nestedhvm into SVM
- Renamed struct nestedhvm to struct nestedvcpu
- Reworked VMRUN and VMEXIT emulation. It uses a defered emulation
  mechanism that makes interrupt handling more efficient and is closer
  to what VMX is doing
- VMCB is peristent mapped. Only remap the VMCB when l1 guest
  changes the address.


The patch series:

patch 01: add nestedhvm guest config option to the tools.
                 This is the only one patch touching the tools
patch 02: Add data structures for nested virtualization.
patch 03: add nestedhvm function hooks.
patch 04: The heart of nested virtualization.
patch 05: Allow switch to paged real mode during vmrun emulation.
                 Emulate cr0 and cr4 when guest does not intercept them
                 (i.e. Hyper-V/Windows7, KVM)
patch 06: When injecting an exception into nested guest, inject
                 #VMEXIT into the guest if intercepted.
patch 07: Allow guest to enable SVM in EFER only on AMD.
patch 08: Handle interrupts (generic part).
patch 09: SVM specific implementation for nested virtualization.
patch 10: Handle interrupts (SVM specific).
patch 11: The piece of code that effectively turns on nested virtualization.
patch 12: Move dirty_vram from struct hvm_domain to struct p2m_domain.
                 This change is the first part from a larger not-yet-ready
                 change where the vram and log_dirty tracking is teached
                 to work on per p2m.
patch 13: Handle nested pagefault to enable hap-on-hap and handle
                 nested guest page-table-walks to emulate instructions
                 the guest does not intercept (i.e. WBINVD with Windows 7).


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I'd like to ask a general question on nested virtualization. Can an L1 or L>1 VM span multiple physical machines?

I'm guessing not from the pdf, http://lists.xensource.com/archives/html/xen-devel/2010-04/pdfsVHwQIeZLB.pdf, but I wanted to ask and confirm because if so, this would be a fantastic way to segregate individual customer infrastructures in a cloud environment. 

Thanks

-Bruce

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