VME support was broken on Ryzen for a while before a microcode patch came out. The VME instructions are a relatively obscure, and originally Intel proprietary

VME support was broken on Ryzen for a while before a microcode patch came out. The VME instructions are a relatively obscure, and originally Intel proprietary extension, to i386's virtual 8086 mode. Introduced in the 90s to speed up DOS virtual machines under OS/2 and NT, I think. I don't know much about how stuff is implemented these days, but virtual 8086 mode involves some page table muckery and similar. Surely implementing it creates a larger exposure area, from a security standpoint.