intel-ucode 20201112-1 causes hang on boot

Inizia esaminando le revisioni di intel-ucode segnalate e l’output di journalctl, bsdtar, iucode_tool e lscpu per l’Intel Core i7-6500U. Verifica se la revisione 0x00e2 causa in modo consistente il blocco all’avvio rispetto alla 0x00d6, utilizzando la firma del processore segnalata come caso di test. Il lavoro è completato quando il problema è stato riprodotto o escluso e sono documentate la revisione interessata e la risoluzione necessaria.

Using Manjaro and with the latest update I upgraded the intel-ucode package from 20200616-1 to 20201112-1.
After a reboot the system didn't load anymore, and chrooting from a live usb, the journal doesn't show any messages from the last boot (after the upgrade).

Broken revision:
sig 0x000406e3, 2020-07-14, rev 0x00e2

Last known working revision:
sig 0x000406e3, 2019-10-03, rev 0x00d6

Before the upgrade:

$ journalctl -b | grep microcode
Nov 21 18:05:38 asus kernel: microcode: microcode updated early to revision 0xd6, date = 2019-10-03
Nov 21 18:05:38 asus kernel: SRBDS: Vulnerable: No microcode
Nov 21 18:05:38 asus kernel: microcode: sig=0x406e3, pf=0x80, revision=0xd6
Nov 21 18:05:38 asus kernel: microcode: Microcode Update Driver: v2.2.

$ bsdtar -Oxf /boot/intel-ucode.img | iucode_tool -tb -lS -
iucode_tool: system has processor(s) with signature 0x000406e3
microcode bundle 1: (stdin)
selected microcodes:
  001/159: sig 0x000406e3, pf_mask 0xc0, 2019-10-03, rev 0x00d6, size 101376

After the upgrade

$ bsdtar -Oxf /boot/intel-ucode.img | iucode_tool -tb -lS -
iucode_tool: system has processor(s) with signature 0x000406e3
microcode bundle 1: (stdin)
selected microcodes:
  001/159: sig 0x000406e3, pf_mask 0xc0, 2020-07-14, rev 0x00e2, size 105472

CPU

$ lscpu
Architecture:                    x86_64
CPU op-mode(s):                  32-bit, 64-bit
Byte Order:                      Little Endian
Address sizes:                   39 bits physical, 48 bits virtual
CPU(s):                          4
On-line CPU(s) list:             0-3
Thread(s) per core:              2
Core(s) per socket:              2
Socket(s):                       1
NUMA node(s):                    1
Vendor ID:                       GenuineIntel
CPU family:                      6
Model:                           78
Model name:                      Intel(R) Core(TM) i7-6500U CPU @ 2.50GHz
Stepping:                        3
CPU MHz:                         499.773
CPU max MHz:                     3100.0000
CPU min MHz:                     400.0000
BogoMIPS:                        5202.65
Virtualization:                  VT-x
L1d cache:                       64 KiB
L1i cache:                       64 KiB
L2 cache:                        512 KiB
L3 cache:                        4 MiB
NUMA node0 CPU(s):               0-3
Vulnerability Itlb multihit:     KVM: Mitigation: VMX disabled
Vulnerability L1tf:              Mitigation; PTE Inversion; VMX conditional cache flushes, SMT vulnerable
Vulnerability Mds:               Mitigation; Clear CPU buffers; SMT vulnerable
Vulnerability Meltdown:          Mitigation; PTI
Vulnerability Spec store bypass: Mitigation; Speculative Store Bypass disabled via prctl and seccomp
Vulnerability Spectre v1:        Mitigation; usercopy/swapgs barriers and __user pointer sanitization
Vulnerability Spectre v2:        Mitigation; Full generic retpoline, IBPB conditional, IBRS_FW, STIBP conditional, RSB filling
Vulnerability Srbds:             Vulnerable: No microcode
Vulnerability Tsx async abort:   Not affected
Flags:                           fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss
                                  ht tm pbe syscall nx pdpe1gb rdtscp lm constant_tsc art arch_perfmon pebs bts rep_good nopl xtopology nonsto
                                 p_tsc cpuid aperfmperf pni pclmulqdq dtes64 monitor ds_cpl vmx est tm2 ssse3 sdbg fma cx16 xtpr pdcm pcid sse
                                 4_1 sse4_2 x2apic movbe popcnt tsc_deadline_timer aes xsave avx f16c rdrand lahf_lm abm 3dnowprefetch cpuid_f
                                 ault epb invpcid_single pti ssbd ibrs ibpb stibp tpr_shadow vnmi flexpriority ept vpid ept_ad fsgsbase tsc_ad
                                 just bmi1 avx2 smep bmi2 erms invpcid mpx rdseed adx smap clflushopt intel_pt xsaveopt xsavec xgetbv1 xsaves 
                                 dtherm ida arat pln pts hwp hwp_notify hwp_act_window hwp_epp md_clear flush_l1d

Let me know if I should try out anything, or if more information is needed.