Re: [RFC PATCH v4 05/26] x86/sgx: Introduce virtual EPC for use by KVM guests

Jarkko Sakkinen
2021-02-09T23:36:04Z

On Mon, Feb 08, 2021 at 11:54:09PM +1300, Kai Huang wrote:
> From: Sean Christopherson <sean.j.christopherson@intel.com>
>
> Add a misc device /dev/sgx_vepc to allow userspace to allocate "raw" EPC
> without an associated enclave. The intended and only known use case for
> raw EPC allocation is to expose EPC to a KVM guest, hence the 'vepc'
> moniker, virt.{c,h} files and X86_SGX_KVM Kconfig.

This commit message does give existential background for having vEPC.
I.e. everything below this paragraph is "good enough" to make the case
for SGX subsystem controlled vEPC.

However, it does not give any existential background for /dev/sgx_vpec.
Even with differing internals you could just as well make the whole
thing as subfunction of /dev/sgx_enclave. It's perfectly doable. It
does not really matter how much the same internals are used (e.g.
sgx_encl).

Without that clearly documented, it would be unwise to merge this.

/Jarkko