>
> 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).
Alternatively, I think we can also add check to disable TDX when 'maxcpus' has
been specified, but I think the current way is better.
>
> btw your comment said that 'maxcpus' is basically an invalid mode
> due to MCE broadcase problem. I didn't find any code to block it when
> MCE is enabled,
Please see below comment in cpu_smt_allowed():
static inline bool cpu_smt_allowed(unsigned int cpu)
{
...
/*
* On x86 it's required to boot all logical CPUs at least once so
* that the init code can get a chance to set CR4.MCE on each
* CPU. Otherwise, a broadcasted MCE observing CR4.MCE=0b on any
* core will shutdown the machine.
*/
return !cpumask_test_cpu(cpu, &cpus_booted_once_mask);
}
> thus wonder the rationale behind and whether that
> rationale can be brought to this series (i.e. no check against those
> conflicting boot options and just let SEAMCALL itself to detect and fail).
>
> @Thomas, any guidance here?
>
> Thanks
> Kevin
