Comment 4 for bug 1743100

4.13.0-31-generic boots for me and behaves as expected (no issues) However, variant one is still active:

Spectre and Meltdown mitigation detection tool v0.31

Checking for vulnerabilities against running kernel Linux 4.13.0-31-generic #34~16.04.1-Ubuntu SMP Fri Jan 19 17:11:01 UTC 2018 x86_64
CPU is Intel(R) Core(TM) i7-7500U CPU @ 2.70GHz

CVE-2017-5753 [bounds check bypass] aka 'Spectre Variant 1'
* Checking count of LFENCE opcodes in kernel: YES
> STATUS: NOT VULNERABLE (114 opcodes found, which is >= 70, heuristic to be improved when official patches become available)

CVE-2017-5715 [branch target injection] aka 'Spectre Variant 2'
* Mitigation 1
* Hardware (CPU microcode) support for mitigation
* The SPEC_CTRL MSR is available: NO
* The SPEC_CTRL CPUID feature bit is set: NO
* Kernel support for IBRS: YES
* IBRS enabled for Kernel space: NO
* IBRS enabled for User space: NO
* Mitigation 2
* Kernel compiled with retpoline option: NO
* Kernel compiled with a retpoline-aware compiler: NO
> STATUS: VULNERABLE (IBRS hardware + kernel support OR kernel with retpoline are needed to mitigate the vulnerability)

CVE-2017-5754 [rogue data cache load] aka 'Meltdown' aka 'Variant 3'
* Kernel supports Page Table Isolation (PTI): YES
* PTI enabled and active: YES
* Checking if we're running under Xen PV (64 bits): NO
> STATUS: NOT VULNERABLE (PTI mitigates the vulnerability)

A false sense of security is worse than no security at all, see --disclaimer