Nested page fault

  • Translation failure with nested paging structures causes VM exit

    • Intel: EPT violation (and few more 📖29.3.3 EPT-Induced VM Exits)
    • AMD: #VMEXIT(NPF)

  • Few read-only fields are updated with the details of a failure

    Fault reasonsGPA tried to translateVA tried to translate
    IntelExit qualificationGuest-physical addressGuest linear address
    AMDEXITINFO1EXITINFO2Not Available
    • Intel: 📖Table 28-7. Exit Qualification for EPT Violations
    • AMD: 📖15.25.6 Nested versus Guest Page Faults, Fault Ordering

  • Typical actions by a hypervisor

    • update nested paging structure(s) and let the guest retry the same operation
      • may require TLB invalidation, like an OS has to when it changes paging structures
    • inject an exception to the guest to prevent access