Re: [Bug 53611] New: nVMX: Add nested EPT

[Jan Kiszka <jan.kiszka@siemens.com>]

On 2013-02-11 13:49, bugzilla-daemon@bugzilla.kernel.org wrote:
> https://bugzilla.kernel.org/show_bug.cgi?id=53611
> 
>            Summary: nVMX: Add nested EPT
>            Product: Virtualization
>            Version: unspecified
>           Platform: All
>         OS/Version: Linux
>               Tree: Mainline
>             Status: NEW
>           Severity: normal
>           Priority: P1
>          Component: kvm
>         AssignedTo: virtualization_kvm@kernel-bugs.osdl.org
>         ReportedBy: nyh@math.technion.ac.il
>         Regression: No
> 
> 
> Created an attachment (id=93101)
>  --> (https://bugzilla.kernel.org/attachment.cgi?id=93101)
> Nested EPT patches, v2
> 
> Nested EPT means emulating EPT for an L1 guest, allowing it to use EPT when
> running a nested guest L2. When L1 uses EPT, it allows the L2 guest to set
> its own cr3 and take its own page faults without either of L0 or L1 getting
> involved. In many workloads this significanlty improves L2's performance over
> the previous two alternatives (shadow page tables over ept, and shadow page
> tables over shadow page tables). As an example, I measured a single-threaded
> "make", which has a lot of context switches and page faults, on the three
> options:
> 
>  shadow over shadow: 105 seconds
>  shadow over EPT: 87 seconds      (this is the default currently)
>  EPT over EPT: 29 seconds
> 
>  single-level virtualization (with EPT): 25 seconds
> 
> So clearly nested EPT would be a big win for such workloads.
> 
> I attach a patch set which I worked on and allowed me to measure the above
> results. This is the same patch set I sent to KVM mailing list on August 1st,
> 2012, titled "nEPT v2: Nested EPT support for Nested VMX".
> 
> This patch set still needs some work: it is known to only work in some setups
> but not others, and the file "announce" in the attached tar lists 5 things
> which definitely need to be done. There were a few additional comments in the
> mailing list - see
> http://comments.gmane.org/gmane.comp.emulators.kvm.devel/95395
> 

I suppose they do not apply anymore as well. Do you have a recent tree
around somewhere or plan to resume work on it?

Jan

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