On Tue, 2022-03-29 at 00:47 +1300, Tian, Kevin wrote: > > From: Huang, Kai <kai.huang@xxxxxxxxx> > > Sent: Monday, March 28, 2022 5:24 PM > > > > > > cpu_present_mask does not always represent BIOS-enabled CPUs due > > > to those boot options. Then why do we care whether CPUs in this mask > > > (if only representing a subset of BIOS-enabled CPUs) are at least brought > > > up once? It will fail at TDH.SYS.CONFIG anyway. > > > > As I said, this is used to make sure SEAMRR has been detected on all cpus, > > so > > that any BIOS misconfiguration on SEAMRR has been detected. Otherwise, > > seamrr_enabled() may not be reliable (theoretically). > > *all cpus* is questionable. > > Say BIOS enabled 8 CPUs: [0 - 7] > > cpu_present_map covers [0 - 5], due to nr_cpus=6 > > You compared cpus_booted_once_mask to cpu_present_mask so if maxcpus > is set to a number < nr_cpus SEAMRR is considered disabled because you > cannot verify CPUs between [max_cpus, nr_cpus). SEAMRR is not considered as disabled in this case, at least in my intention. My understanding on the spec is if SEAMRR is configured as enabled on one core (the SEAMRR MSRs are core-scope), the SEAMCALL instruction can work on that core. It is TDX's requirement that some SEAMCALL needs to be done on all BIOS-enabled CPUs to finish TDX initialization, but not SEAM's.
