Speed up Windows 10 with the Retpoline Spectre fix

It's been a while since we heard much about Spectre, the speculative execution exploit that sent the security world into a frenzy. Cast your mind back a little while and you'll probably remember that the various fixes that were produced to mitigate against the exploits all had one thing in common -- they resulted in a performance hit.

To help address the reduced performance experienced on older AMD and Intel systems, a new mitigation technique called Retpoline was developed. This new Spectre patch is currently included in Insider builds of Windows 10, but you can install it and enable it right now -- regardless of whether you are signed up for the Insider program -- and enjoy a speed boost for your computer.

See also:

• Confused about what Windows 10 test builds are in which Insider ring? There's an easy way to find out
• Microsoft releases Windows 10 19H1 Build 18351 to the Fast ring
• Windows 10 loses share as Windows 7 makes significant gains

Having made Retpoline available to Windows 10 19H1, Microsoft is now also making the patch available to anyone running the Windows 10 October 2018 Update. As the company explains in the support article for Windows update KB4482887, the patch " Enables 'Retpoline' for Windows on certain devices, which may improve performance of Spectre variant 2 mitigations (CVE-2017-5715)".

Retpoline is being made available as part of a phased rollout, but it is possible to manually enable it by tweaking the registry. As Microsoft explains in an updated version of a blog post from the beginning of this month, there are different registry edits depending on whether you're using Windows 10 or Windows Server. These can be entered at an elevated Command Prompt:

On Client SKUs:

1. reg add "HKLM\SYSTEM\CurrentControlSet\Control\Session Manager\Memory Management" /v FeatureSettingsOverride /t REG_DWORD /d 0x400
2. reg add "HKLM\SYSTEM\CurrentControlSet\Control\Session Manager\Memory Management" /v FeatureSettingsOverrideMask /t REG_DWORD /d 0x400
3. Reboot

On Server SKUs:

1. reg add "HKLM\SYSTEM\CurrentControlSet\Control\Session Manager\Memory Management" /v FeatureSettingsOverride /t REG_DWORD /d 0x400
2. reg add "HKLM\SYSTEM\CurrentControlSet\Control\Session Manager\Memory Management" /v FeatureSettingsOverrideMask /t REG_DWORD /d 0x401
3. Reboot

Please note, however, Microsoft's warning:

Since Retpoline is a performance optimization for Spectre Variant 2, it requires that hardware and OS support for branch target injection to be present and enabled. Skylake and later generations of Intel processors are not compatible with Retpoline, so only Import Optimization will be enabled on these processors.

If you want to some read technical details of the Retpoline mitigation, Google has more information available here -- and Microsoft's guide is also highly informative.

Image credit: Mashka / Shutterstock