On Wed, Nov 07, 2018 at 12:56:58PM -0800, Dave Hansen wrote: > On 11/7/18 11:01 AM, Sean Christopherson wrote: > > Going off comments in similar code related to UMIP, we'd need to figure > > out how to handle protection keys. > > There are two options: > 1. Don't depend on the userspace mapping. Do get_user_pages() to find > the instruction in the kernel direct map, and use that. > 2. Do a WRPKRU that allows read access, do the read, then put PKRU back. > This is a pain because of preemption and all that jazz. > > Right now, we just let the prefetch instruction detection fail if you > mark it unreadable with pkeys. Tough cookies, basically. But, that's > just the kernel being nice, but you need it for functionality, so it's > tougher. I would go with one because it is the stable way to do it and we are 100% sure to not conflict with pk's. /Jarkko
