On Mon, Aug 17, 2020 at 9:24 PM Sean Christopherson <sean.j.christopherson@xxxxxxxxx> wrote: > > Allow userspace to exit the vDSO on interrupts that are acknowledged > while the enclave is active. This allows the user's runtime to switch > contexts at opportune times without additional overhead, e.g. when using > an M:N threading model (where M user threads run N TCSs, with N > M). This is IMO rather odd. We don't support this type of notification on interrupts for normal user code. The fact user code can detect interrupts during enclave execution is IMO an oddity of SGX, and I have asked Intel to consider replacing the AEX mechanism with something more transparent to user mode. If this ever happens, this mechanism is toast. Even without architecture changes, building a *reliable* M:N threading mechanism on top of this will be difficult or impossible, as there is no particular guarantee that a thread will get timing interrupts at all or that these interrupts will get lucky and hit enclave code, thus triggering an AEX. We certainly don't, and probably never will, support any corresponding feature for non-enclave code. So this seems like an odd, and possibly unsupportable, feature to add. --Andy
