mITX: kernel brings up only 4 cores (of 8)

[asheplyakov]

Sometimes (approximately once in 5 -- 10) boots the kernel fails to initialize CPU cores 4 -- 7:

[    0.304752] Detected PIPT I-cache on CPU1
[    0.304781] GICv3: CPU1: found redistributor 1 region 0:0x000000002d120000
[    0.304829] CPU1: using LPI pending table @0x00000009f64e0000
[    0.304896] CPU1: Booted secondary processor [411fd073]
[    0.313915] Detected PIPT I-cache on CPU2
[    0.313944] GICv3: CPU2: found redistributor 100 region 0:0x000000002d140000
[    0.313995] CPU2: using LPI pending table @0x00000009f6530000
[    0.314058] CPU2: Booted secondary processor [411fd073]
[    0.323049] Detected PIPT I-cache on CPU3
[    0.323071] GICv3: CPU3: found redistributor 101 region 0:0x000000002d160000
[    0.323119] CPU3: using LPI pending table @0x00000009f65a0000
[    0.323175] CPU3: Booted secondary processor [411fd073]
[    1.375700] CPU4: failed to come online
[    1.454139] CPU4: failed in unknown state : 0x0
[    2.480133] CPU5: failed to come online
[    2.484534] CPU5: failed in unknown state : 0x0
[    3.523045] CPU6: failed to come online
[    3.527514] CPU6: failed in unknown state : 0x0
[    4.566661] CPU7: failed to come online
[    4.571178] CPU7: failed in unknown state : 0x0
[    4.576643] Brought up 4 CPUs
[    4.580128] SMP: Total of 4 processors activated.

The problem has never been observed during a "cold" boot (i.e. if the power has been physically disconnected
from the system before turning it on)

The problem happens only with mITX board.