Description: Post-Barrier Return Stack Buffer Predictions (PBRSB)
References:
 https://www.intel.com/content/www/us/en/security-center/advisory/intel-sa-00706.html
 https://www.intel.com/content/www/us/en/developer/articles/technical/software-security-guidance/advisory-guidance/post-barrier-return-stack-buffer-predictions.html
Notes:
 carnil> Fixed as well in 5.18.17 for 5.18.y and 5.19.1 for 5.19.y.
Bugs:
upstream: released (6.0-rc1) [2b1299322016731d56807aa49254a5ea3080b6b3, ba6e31af2be96c4d0536f2152ed6f7b6c11bca47]
5.10-upstream-stable: released (5.10.136) [509c2c9fe75ea7493eebbb6bb2f711f37530ae19, 1bea03b44ea2267988cce064f5887b01d421b28c]
4.19-upstream-stable: released (4.19.255) [b6c5011934a15762cd694e36fe74f2f2f93eac9b, b1c9f470fb724d3cfd6cf8fe4a70c2ec4de2e9f4]
sid: released (5.18.16-1) [bugfix/x86/pbrsb/0001-x86-speculation-Add-RSB-VM-Exit-protections.patch, bugfix/x86/pbrsb/0002-x86-speculation-Add-LFENCE-to-RSB-fill-sequence.patch]
5.10-bullseye-security: released (5.10.136-1)
4.19-buster-security: released (4.19.260-1)