On Sat, Nov 3, 2018 at 1:17 AM Jarkko Sakkinen <jarkko.sakkinen@xxxxxxxxxxxxxxx> wrote: > > From: Sean Christopherson <sean.j.christopherson@xxxxxxxxx> > > Like SGX itself, SGX Launch Control must be explicitly enabled via a > flag in IA32_FEATURE_CONTROL. Clear the SGX_LC capability if Launch > Control is not fully enabled (or obviously if SGX itself is disabled). > > Note that clearing X86_FEATURE_SGX_LC creates a bit of a conundrum > regarding the SGXLEPUBKEYHASH MSRs, as it may be desirable to read the > MSRs even if they are not writable, e.g. to query the configured key, > but clearing the capability leaves no breadcrum for discerning whether > or not the MSRs exist. But, such usage will be rare (KVM is the only > known case at this time) and not performance critical, so it's not > unreasonable to require the use of rdmsr_safe(). Clearing the cap bit > eliminates the need for an additional flag to track whether or not > Launch Control is truly enabled, which is what we care about the vast > majority of the time. > @@ -618,6 +618,8 @@ static void detect_sgx(struct cpuinfo_x86 *c) > setup_clear_cpu_cap(X86_FEATURE_SGX1); > setup_clear_cpu_cap(X86_FEATURE_SGX2); > } > + if (unsupported || !(fc & FEATURE_CONTROL_SGX_LE_WR)) > + setup_clear_cpu_cap(X86_FEATURE_SGX_LC); > } A-ha, I see how you use this variable here (though it's still possible to get rid of it, choose what is better for readability / maintenance). -- With Best Regards, Andy Shevchenko
