Comment 111 for bug 1779827

Adding my $0.02, whatever it is worth. I ran into this on a RamNode VPS. downgrading to 4.15.0-20-generic made it boot again. Attaching dmesg from that machine.
$ cat /proc/cpuinfo
processor : 0
vendor_id : GenuineIntel
cpu family : 6
model : 58
model name : Intel(R) Xeon(R) CPU E3-1240 V2 @ 3.40GHz
stepping : 9
microcode : 0x1
cpu MHz : 3400.022
cache size : 4096 KB
physical id : 0
siblings : 1
core id : 0
cpu cores : 1
apicid : 0
initial apicid : 0
fpu : yes
fpu_exception : yes
cpuid level : 13
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ss syscall nx lm constant_tsc arch_perfmon nopl cpuid pni pclmulqdq ssse3 cx16 pcid sse4_1 sse4_2 x2apic popcnt tsc_deadline_timer aes xsave avx f16c rdrand hypervisor lahf_lm pti fsgsbase smep xsaveopt ibpb ibrs stibp
bugs : cpu_meltdown spectre_v1 spectre_v2
bogomips : 6800.04
clflush size : 64
cache_alignment : 64
address sizes : 36 bits physical, 48 bits virtual
power management: