Windows 10 bootloader freezes with more than one CPU

[maxried]

When running Windows 10 64bit as guest, as soon as I add more than one CPU to the VM, it does not boot beyond the cyan colored Windows logo no matter if it's a working installation of Windows 10 or the installer disc. This happens on 5.0.14 as well as on 5.0.x revision 105205.

I'm on Ubuntu Wily, all installed packages up to date.

# uname -a
Linux wilma 4.2.0-27-generic #32-Ubuntu SMP Fri Jan 22 04:49:08 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux

# vboxmanage -v
5.0.14r105127

# lscpu
Architecture:          x86_64
CPU op-mode(s):        32-bit, 64-bit
Byte Order:            Little Endian
CPU(s):                4
On-line CPU(s) list:   0-3
Thread(s) per core:    1
Core(s) per socket:    4
Socket(s):             1
NUMA node(s):          1
Vendor ID:             GenuineIntel
CPU family:            6
Model:                 55
Model name:            Intel(R) Pentium(R) CPU  N3540  @ 2.16GHz
Stepping:              8
CPU MHz:               502.702
CPU max MHz:           2665,6001
CPU min MHz:           499,8000
BogoMIPS:              4326.40
Virtualization:        VT-x
L1d cache:             24K
L1i cache:             32K
L2 cache:              1024K
NUMA node0 CPU(s):     0-3

# dmesg | grep microcode
[    1.221254] microcode: CPU0 sig=0x30678, pf=0x8, revision=0x829
[    1.221270] microcode: CPU1 sig=0x30678, pf=0x8, revision=0x829
[    1.221287] microcode: CPU2 sig=0x30678, pf=0x8, revision=0x829
[    1.221304] microcode: CPU3 sig=0x30678, pf=0x8, revision=0x829
[    1.221427] microcode: Microcode Update Driver: v2.00 <tigran@aivazian.fsnet.co.uk>, Peter Oruba

[maxried]

VBox.log when run with 2 CPUs

[maxried]

VBox.log when successfully run with 1 CPUs

[maxried]

I just tried the VirtualBox 5.0.0 release and experienced my entire host even freezing (not panicking or oopsing, real freezing!) when starting the VM with more than one CPU attached.

[maxried]

A Windows 7 64bit guest boots fine.

[Frank Mehnert]

Duplicate of #14915.

[Frank Mehnert]

Actually could yould you check if this test build fixes your problem? The reason was most likely the access to the IA32_AUX_TSC MSR.