Newer kernels have this:
$ ls /sys/devices/system/cpu/vulnerabilities
meltdown spectre_v1 spectre_v2
$ cat /sys/devices/system/cpu/vulnerabilities/meltdown
Mitigation: PTI
I wonder if we should export these as metrics in node_exporter:
node_kernel_vulnerabilities{name="meltdown", value="Mitigation: PTI"} 1