Re: [PATCH V5 15/31] x86/sgx: Support restricting of enclave page permissions

[zhubojun]

Hi, Reinette, thanks for your great contribution for EDMM Linux kernel patch. I am trying to follow the newest patch now, and I have some questions on it.

It seems that `sgx_enclave_restrict_permissions()` is able to do permission restrictions for multiple enclave’s pages. After driver invokes ENCLS[EMODPR] to restrict the page’s permission, it should then invoke ENCLS[ETRACK] and send IPIs to ensure stale TLB entries have been flushed. Only in this way, ENCLU[EACCEPT] inside enclave can only succeed.

Current implementation invokes `sgx_enclave_etrack(encl)` after every `__emodpr(…)` in the for loop. My question is:

Can we move the `sgx_enclave_etrack(encl)` out of the for loop? After doing so, `sgx_enclave_etrack(encl)` is invoked **one** time for multiple enclave pages’ permission restriction, instead of N times (N = `modp -> length / PAGE_SIZE`). We may gain some performance optimization from it.

Please correct my if my understanding is incorrect. Looking forward to your reply and Thanks for your time!

BR,
Bojun