@ rene, .......
Linus Torvald/kernel.org's Linux kernel 4.15 has the Retpoline feature for Spectre 2 built-in, but not for the IBRS/IBPB features, whereas Canonical Inc/Ubuntu(and Red Hat)'s latest patched Linux kernels are adopting the IBRS/IBPB features for Spectre 2 but not for Retpoline.
... But Intel's David Woodhouse has stated that Retpoline does not work for SkyLake CPUs.
So, what will likely happen is for both Linus Torvald/kernel.org and Canonical Inc/Ubuntu to adopt both the Retpoline and IBRS/IBPB features to patch for Spectre 2. If so, LM users will then have the choice of using either one or both features for Spectre 2, eg SkyLake users will install the appropriate kernel update and Intel microcode update for the IBRS/IBPB features, while non-Skylake users can opt to install only the kernel update for the Retpoline feature or install both updates for both the Retpoline and IBRS/IBPB features.
Which features will future Intel CPUs build-in for Meltdown and Spectre.?
_ _ _ _ _ _ _
EDIT & CORRECTION
; Looks like kernel.org's Linux kernel 4.15 also supports Intel SkyLake CPUs for Retpoline, as per ... https://www.phoronix.com/scan.php?page= ... Benchmarks
(17 Jan 2018 - Benchmarking Retpoline Underflow Protection With Intel Skylake/Kabylake)
... So, Linux users will likely just need to use the Retpoline feature for Spectre 2, ie no need to install any CPU microcode updates for the IBRS/IBPB features that also patch for Spectre 2. If so, Canonical Inc/Ubuntu will have to release new kernel updates to revert the IBRS/IBPB features presently contained in 3.13.141, 4.4.112 and 4.13.32.
What will happen to Windows systems wrt Spectre 2.? Does Windows has a similar Retpoline feature in its kernel.?
... https://www.crowdstrike.com/blog/chip-f ... -mitigate/
(11 Jan 2018)
Without the microcode update, Google’s software workaround (the retpoline) can be used, but it requires custom compiler support and recompiled binaries which leverage the technique. GCC as well as Clang/LLVM, the major open source compilers, now have support for generating such retpolines, while Windows and Visual Studio are not currently pursuing this approach.
http://www.zdnet.com/article/google-our ... ll-use-it/
(12 Jan 2018)
Google: Our brilliant Spectre fix dodges performance hit, so you should all use it.
Google wants the whole industry to adopt its Retpoline fixes for Variant 2 of the Meltdown-Spectre bugs.
https://www.phoronix.com/scan.php?page= ... ne-Patches
(4 Jan 2018 - More Linux Kernel & GCC Patches Come Out In The Wake Of Spectre+Meltdown)
https://www.phoronix.com/scan.php?page= ... -Published
(6 Jan 2018 - Retpoline v5 Published For Fending Off Spectre Branch Target Injection)