Nested paging exposed to the guest

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Nested paging exposed to the guest

Postby mhanor » 24. Sep 2019, 22:01

Is it possible to expose Nested Paging (EPT/NPT) to the guest?
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Re: Nested paging exposed to the guest

Postby socratis » 24. Sep 2019, 23:24

"EPT" as in "Ept - Extended Page Tables"? If so, everything I've seen so far[1] has the following entry in the VBox.log:
00:00:02.439949 Nested hardware virtualization - VMX features
00:00:02.439949 Mnemonic - Description = guest (host)
...
00:00:02.439978 Ept - Extended Page Tables = 0 (1)

I have yet to see a "1 (1)" case, which means no, not at the moment at least...


[1]: I've been collecting an assortment of CPUs (since 6.1.0b1 came out) trying to see what capabilities each one has, and see if they're nested-virtualization capable.
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Re: Nested paging exposed to the guest

Postby Technologov » 25. Sep 2019, 14:01

I think EPT/NPT is necessary requirement for some hypervisors, including Hyper-V.
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Re: Nested paging exposed to the guest

Postby mhanor » 25. Sep 2019, 14:07

Correct, that's why I'm asking.
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Re: Nested paging exposed to the guest

Postby socratis » 25. Sep 2019, 17:38

Seems to me that someone(s) want to run Hyper-V inside a VM... :)

As previously stated in these 6.1.0b1 forums, it's best if you stick on getting "VirtualBox on VirtualBox" running first, and then the other "exotic" (as I call them) scenarios will follow. When you start seeing:
socratis wrote:
00:00:02.439978   Ept - Extended Page Tables  = 1 (1)
in your logs, then you'll know that something might be ready for public testing...
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Re: Nested paging exposed to the guest

Postby mhanor » 25. Sep 2019, 18:02

I'm only looking for a straight answer from a developer, so we can be sure. In the past, I know that you could enable some CPU features or instructions, that weren't enabled by default for the guest.
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Re: Nested paging exposed to the guest

Postby socratis » 25. Sep 2019, 18:41

mhanor wrote:I'm only looking for a straight answer from a developer, so we can be sure

Most of the times, I do seek confirmation before posting an answer, that's how my posts get... "gravitas"! ;)
socratis: EPT/NPT is not something that's passed to the guest, right?
Developer: not yet.

For more details, join the IRC #vbox-dev channel...
Do NOT send me Personal Messages (PMs) for troubleshooting, they are simply deleted.
Do NOT reply with the "QUOTE" button, please use the "POST REPLY", at the bottom of the form.
If you obfuscate any information requested, I will obfuscate my response. These are virtual UUIDs, not real ones.
socratis
Site Moderator
 
Posts: 27690
Joined: 22. Oct 2010, 11:03
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