[vbox-dev] Arrangement of EPT structures with SMP

[Sander van Leeuwen]

Each VCPU has its own root page table, but all VCPUs are sharing the 
same one with EPT (or AMD nested paging for that matter).

Tom Birch wrote:
> Cool, thanks, that's what I thought. Is there any reason the EPT is a
> per-VCPU data structure? Could you please point me to the bits of code
> that do this sharing? I'm getting lost looking at all the assignments
> to the pShwPageCR3* variables, they still all seem to be per-VCPU, I
> can't find where it hooks into the root VM structure.
>
> cheers,
> Tom
>
> On Thu, Oct 29, 2009 at 1:19 PM, Sander van Leeuwen
> <Sander.Vanleeuwen at sun.com> wrote:
>   
>> The EPT structures are shared between all VCPUs as they contain a guest
>> physical to host physical mapping, which
>> is independent of the VCPU. The host OS is irrelevant.
>>
>> Tom Birch wrote:
>>     
>>> I'm looking through the page management code, specifically hardware
>>> acceleration on Intel with EPT, and I can't quite figure out the
>>> high-level relationships between various structures. Both the VMCS and
>>> EPTP seem to be per-PVMCPU data structures, does this mean that within
>>> a single VM, you can have multiple distinct EPTPs (on different
>>> VCpus), or is this arrangement just a consequence of the way shadow
>>> paging worked before EPT? Put another way, can I guarantee that all
>>> VCpus within a single VM will all share the same EPTP? I'm mainly
>>> concerned about how this applies to Darwin if that matters, but I
>>> seems like a fairly Host-OS-agnostic feature.
>>>
>>> cheers,
>>> Tom
>>>
>>> _______________________________________________
>>> vbox-dev mailing list
>>> vbox-dev at virtualbox.org
>>> http://vbox.innotek.de/mailman/listinfo/vbox-dev
>>>
>>>       
>> --
>> Kind regards / Mit freundlichen Gruessen / Met vriendelijke groet
>>
>> --
>>
>> Sun Microsystems GmbH        Sander van Leeuwen
>> Werkstrasse 24               Senior Staff Engineer, VirtualBox
>> 71384 Weinstadt, Germany     mailto:Sander.Vanleeuwen at sun.com
>>
>>
>> ================================================
>> Sitz der Gesellschaft: Sun Microsystems GmbH,
>> Sonnenallee 1, 85551 Kirchheim-Heimstetten
>> Amtsgericht Muenchen: HRB 161028
>> Geschaeftsfuehrer: Thomas Schroeder,
>> Wolfgang Engels, Dr. Roland Boehmer
>> Vorsitzender des Aufsichtsrates: Martin Haering
>> ================================================
>>
>>
>>     


-- 
Kind regards / Mit freundlichen Gruessen / Met vriendelijke groet

-- 

Sun Microsystems GmbH        Sander van Leeuwen
Werkstrasse 24               Senior Staff Engineer, VirtualBox
71384 Weinstadt, Germany     mailto:Sander.Vanleeuwen at sun.com


================================================
Sitz der Gesellschaft: Sun Microsystems GmbH,
Sonnenallee 1, 85551 Kirchheim-Heimstetten
Amtsgericht Muenchen: HRB 161028
Geschaeftsfuehrer: Thomas Schroeder,
Wolfgang Engels, Dr. Roland Boehmer
Vorsitzender des Aufsichtsrates: Martin Haering
================================================