On Fri, Nov 02, 2018 at 04:56:36PM +0000, Jethro Beekman wrote: > On 2018-11-02 09:52, Sean Christopherson wrote: > >On Fri, Nov 02, 2018 at 04:37:10PM +0000, Jethro Beekman wrote: > >>On 2018-11-02 09:30, Sean Christopherson wrote: > >>>... The intended convention for EENTER is to have an ENCLU at the AEX target ... > >>> > >>>... to further enforce that the AEX target needs to be ENCLU. > >> > >>Some SGX runtimes may want to use a different AEX target. > > > >To what end? Userspace gets no indication as to why the AEX occurred. > >And if exceptions are getting transfered to userspace the trampoline > >would effectively be handling only INTR, NMI, #MC and EPC #PF. > > > > Various reasons... > > Userspace may have established an exception handling convention with the > enclave (by setting TCS.NSSA > 1) and may want to call EENTER instead of > ERESUME. The ERESUME trampoline would only be invoked for exceptions that aren't transferred to userspace. On #BR, #UD, etc..., the kernel would fixup %RIP to effectively point at @fault_handler. Userspace can then do whatever it wants to handle the fault, e.g. do EENTER if the fault needs to be serviced by the enclave. > Userspace may want fine-grained control over enclave scheduling (e.g. > SGX-Step) Uh, isn't SGX-Step an attack on SGX? Preventing userspace from playing games with enclave scheduling seems like a good thing.
