Learning about spectre attack

Spectre Attack V2 mitigation is via "retpoline" instruction:

https://www.phoronix.com/scan.php?page=news_item&px=Linux-Retpoline-Rewrite-Rewrite

inside the kernel now for over 3years.

The spectre attack enable reading of privileged memory via side channel attack:

https://googleprojectzero.blogspot.com/2018/01/reading-privileged-memory-with-side.html

The main focus is patching the kernel to provide protection against this form of attack:

https://lwn.net/Articles/743380/

But "retpoline" have serious performance overheads:

https://lwn.net/Articles/774743/

And one of the best write-ups:

https://support.google.com/faqs/answer/7625886

https://www.griffissinstitute.org/what-we-do/gi-lecture-education-series-presentations/giles-retpoline