On 8/23/19 3:52 PM, Nadav Amit wrote: > INVPCID is considerably slower than INVLPG of a single PTE. Using it to > flush the user page-tables when PTI is enabled therefore introduces > significant overhead.
I'm not sure this is worth all the churn, especially in the entry code. For large flushes (> tlb_single_page_flush_ceiling), we don't do INVPCIDs in the first place. I'd really want to understand what the heck is going on that makes INVPCID so slow, first.