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How does a hypervisor work with SGX?

Hello,

I'm studying how SGX works in virtual machines. I'm using KVM-sgx and QEMU-sgx to make a virtual machine that can run SGX applications.

if an SGX app starts to run in the VM, how the hypervisor maps EPC pages that the VM uses to actual EPC pages?

I know all EPC pages are statically allocated and mapped to VM when it is created (https://github.com/01org/kvm-sgx/wiki), but allocating EPC pages to some process is done when an enclave is created in real SGX application world. That means creating a VM is actually creating an SGX enclave, however, it must be false because enclave only runs in user space, while kvm is in kernel space.

Then it should mean that the modified SGX driver included in kvm-sgx has functionality of EPC allocation. I see three commits (6b4962a, b9137fa, and 0e34cb7) regarding to support this functionality. Is it right that these functions are added to allocate EPC pages for virtualization support?

Also, how address translation between guest virtual address and guest physical address is protected by SGX? In a native machine, address translation between virtual address and physical address for EPC pages is protected by TLB miss handler, but there is no information about SGX address translation protection in virtualized environment.

Thanks in advance!

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