Re: [PATCH v1 1/1] x86/tdx: Handle MWAIT, MONITOR and WBINVD

[Dave Hansen]

On 3/30/21 8:00 AM, Andi Kleen wrote:
>>> +	/* MWAIT is not supported in TDX platform, so suppress it */
>>> +	setup_clear_cpu_cap(X86_FEATURE_MWAIT);
>> In fact, MWAIT bit returned by CPUID instruction is zero for TD guest. This
>> is enforced by SEAM module.
> Good point.
>> Do we still need to safeguard it by setup_clear_cpu_cap() here?
> I guess it doesn't hurt to do it explicitly.

If this MWAIT behavior (clearing the CPUID bit) is part of the guest
architecture, then it would also be appropriate to WARN() rather than
silently clearing the X86_FEATURE bit.