Re: Why guest physical addresses are not the same as the corresponding host virtual addresses in QEMU/KVM? Thanks!

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&gt; 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?