specter "fix" makes things slow in virtualbox

[iplayfast]

When using VirtualBox having the specter fix in the kernel makes things deadly slow. (specifically CVE- 2017-5715)

Suggestion, have alternative build of the kernel that does not include the specter fix.

Ref: https://www.zdnet.com/article/linus-torvalds-after-big-linux-performance-hit-spectre-v2-patch-needs-curbs/ https://nakedsecurity.sophos.com/2018/11/26/spectre-mitigation-guts-linux-4-20-performance/

[gm10]

Even if Linux Mint did its own kernels, which it does not, the kernel discussed there has nothing to do with LM19, is not even released yet and the issue has long been fixed. It doesn't get more out of scope of this bug tracker than that.

[iplayfast]

I didn't know that mint didn't do it's own kernels. (why not?) However, just to show the relevance. From my mint 19.

The results from spectre-meltdown-checker.sh on inux 4.15.0-42-generic #45-Ubuntu SMP Thu Nov 15 19:32:57 UTC 2018 x86_64 Specifically (showing that the slow patch is installed): CVE-2017-5715 aka 'Spectre Variant 2, branch target injection'

• Mitigated according to the /sys interface: YES (Mitigation: Full generic retpoline, IBPB, IBRS_FW)
• Mitigation 1
  • Kernel is compiled with IBRS support: YES
  • IBRS enabled and active: YES (for kernel and firmware code)
  • Kernel is compiled with IBPB support: YES
  • IBPB enabled and active: YES
• Mitigation 2
  • Kernel has branch predictor hardening (arm): NO
  • Kernel compiled with retpoline option: YES
  • Kernel compiled with a retpoline-aware compiler: YES (kernel reports full retpoline compilation)
  • Kernel supports RSB filling: YES

    STATUS: NOT VULNERABLE (Full retpoline + IBPB are miti gating the vulnerability) Showing the kernel has the patch in it, which is known to slow things down.

out.txt

[gm10]

I suggest you https://wiki.ubuntu.com/Kernel/BuildYourOwnKernel without the imaginary "slow patch". Good luck. ;)