64-ia-32-architectures-software-developer-system-programming-manual-325384
28.2
When EPT is in use, certain addresses that would normally be treated as physical addresses (and used to
access memory) are instead treated as guest-physical addresses.
Guest-physical addresses are translated by
traversing a set of EPT paging structures to produce physical addresses that are used to access memory.
The translation from guest-physical addresses to physical addresses is determined by a set of EPT paging struc-
tures.
EPT的作用就是用于在vmx non-root模式下转换 guest-physical addresses --> physical addresses
EPT 的主要作用是用于vmx non-root模式. 也就是说，当前的上下文在guest OS环境中。已经不再vmx root, hypervisor中。
【x86|EPT 原理解释】
EPT is used when the “enable EPT” VM-execution control is 1.1 It translates the guest-physical addresses used in
VMX non-root operation
If CR0.PG = 1, the translation of a linear address to a physical address requires multiple translationsof guest-phys-
ical addresses using EPT.
The translation of a 32-bit linear
address then operates as follows:
Bits 31:22 of the linear address select an entry in the guest page directory located at the guest-physical
address in CR3. The guest-physical address of the guest page-directory entry (PDE) is translated through EPT
to determine the guest PDE’s physical address.
Bits 21:12 of the linear address select an entry in the guest page table located at the guest-physical address in
the guest PDE. The guest-physical address of the guest page-table entry (PTE) is translated through EPT to
determine the guest PTE’s physical address.
Bits 11:0 of the linear address is the offset in the page frame located at the guest-physical address in the guest
PTE. The guest-physical address determined by this offset is translated through EPT to determine the physical
address to which the original linear address translates.
In addition to translating a guest-physical address to a physical address, EPT specifies the privileges that software
is allowed when accessing the address.
