[vbox-dev] Arrangement of EPT structures with SMP

Tom Birch froody at gmail.com
Thu Oct 29 20:43:15 GMT 2009

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.


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
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