Hi Sean,
Thank you very much for your thorough explanations. Please see my
inline replies as follows. Thanks!
On Mon, Oct 12, 2020 at 12:54 PM Sean Christopherson
<sean.j.christopherson(a)intel.com> wrote:
No, the guest physical address spaces is not intrinsically tied to the host
virtual address spaces. The fact that GPAs and HVAs are related in KVM is a
property KVM's architecture. EPT/NPT has absolutely nothing to do with HVAs.
As Maxim pointed out, KVM links a guest's physical address space, i.e. GPAs, to
the host's virtual address space, i.e. HVAs, via memslots. For all intents and
purposes, this is an extra layer of address translation that is purely software
defined. The memslots allow KVM to retrieve the HPA for a given GPA when
servicing a shadow page fault (a.k.a. EPT violation).
When EPT is enabled, a shadow page fault due to an unmapped GPA will look like:
GVA -> [guest page tables] -> GPA -> EPT Violation VM-Exit
The above walk of the guest page tables is done in hardware. KVM then does the
following walks in software to retrieve the desired HPA:
GPA -> [memslots] -> HVA -> [host page tables] -> HPA
Do you mean that GPAs are different from their corresponding HVAs when
KVM does the walks (as you said above) in software?
Thanks,
Harry