The erratum SKD002 in http://www.intel.com/content/dam/www/public/us/en/documents/specification-updates/desktop-6th-gen-core-family-spec-update.pdf makes the reader think that BMI extensions aren't supported in Skylake.
It is said that CPUID is "incorrectly indicating the presence of BMI1 or BMI2 instruction set extensions" and that "Attempting to use instructions from the BMI1 or BMI2 instruction set extensions will result in a #UD exception."
I use BMI instructions in some highly optimized part of my software so I wonder what the BIOS workaround is doing:
1) Returns correctly that BMI isn't supported
2) Fix BMI with trap handlers
3) Other TBD
I'll be glad to have detailed explanations from people in the know.