Programmatically Detect if i486 CPU has SL Enhanced Support

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While developing the SIV CPU i486 S-Spec panel I felt SIV should report if the CPU has SL Enhanced support so I added this by checking the i486 S-Specs data.

While doing this I started wondering, is there a defined way to detect if an i486 CPU has SL Enhanced support? I have tried Googling with thus far no luck. Ideally I would like to do this from ring 3 so prefer not to use CRn registers.