Re: [Xen-devel] Fwd: [PATCH 0/18] Nested Virtualization: Overview

[Keir Fraser <keir.fraser@xxxxxxxxxxxxx>]

On 16/04/2010 11:27, "Tim Deegan" <Tim.Deegan@xxxxxxxxxx> wrote:

>> Please read the XenNestedHVM.pdf paper, particularly the section "Software
>> Architecture". This describes how this is made to be generic and what needs
>> to be done to adapt to Intel.
> 
> Your PDFs suggest that even on Intel CPUs, the nested hypervisor should
> always see SVM, not VMX.  You shouldn't be surprised or offended if that
> isn't popular with Intel. :)

I don't see any good argument for it either. I.e., I don't think we care
about migrating between AMD and Intel hosts with nestedhvm enabled, which I
think would be the only argument for it. I know we added support for
cross-emulating SYSENTER and SYSCALL, but that's needed for cross-migration
of any 64-bit guest running compat-mode apps (i.e., really need to make
cross-migration possible at all). I'm sceptical enough of the utility of
cross-vendor migration *at all*, let alone supporting in tandem with
advanced features also of dubious utility (at least in enterprise space),
like nestedhvm.

 -- Keir



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