Hyperthreading enabled in BIOS, but not working under Ubuntu 18.04

I am running a standard Ubuntu 18.04

$  lsb_release -a LSB Version:    core-9.20170808ubuntu1-noarch:security-9.20170808ubuntu1-noarch Distributor ID: Ubuntu Description:    Ubuntu 18.04.2 LTS Release:    18.04 Codename:   bionic 

But I am lacking hyperthreading…. It’s 100% enabled in the BIOS. I disabled and enabled it just to check whether the problem was there, but it’s not… However cpuinfo says: core : 4, siblings : 4, while it should be siblings : 8…

https://ark.intel.com/content/www/us/en/ark/products/88196/intel-core-i7-6700-processor-8m-cache-up-to-4-00-ghz.html

I don’t remember when this happened in my desktop… maybe since the upgrade from 16.04 to 18.04…
Any suggestion is welcome, I am pasting the cpuinfo.

Thanks,

Alex

~$   cat /proc/cpuinfo  processor   : 0 vendor_id   : GenuineIntel cpu family  : 6 model       : 94 model name  : Intel(R) Core(TM) i7-6700 CPU @ 3.40GHz stepping    : 3 microcode   : 0xcc cpu MHz     : 800.004 cache size  : 8192 KB physical id : 0 siblings    : 4 core id     : 0 cpu cores   : 4 apicid      : 0 initial apicid  : 0 fpu     : yes fpu_exception   : yes cpuid level : 22 wp      : yes 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 nonstop_tsc cpuid aperfmperf tsc_known_freq pni pclmulqdq dtes64 monitor ds_cpl vmx smx est tm2 ssse3 sdbg fma cx16 xtpr pdcm pcid sse4_1 sse4_2 x2apic movbe popcnt tsc_deadline_timer aes xsave avx f16c rdrand lahf_lm abm 3dnowprefetch cpuid_fault invpcid_single pti ssbd ibrs ibpb stibp tpr_shadow vnmi flexpriority ept vpid fsgsbase tsc_adjust bmi1 hle avx2 smep bmi2 erms invpcid rtm 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 bugs        : cpu_meltdown spectre_v1 spectre_v2 spec_store_bypass l1tf mds bogomips    : 6816.00 clflush size    : 64 cache_alignment : 64 address sizes   : 39 bits physical, 48 bits virtual power management:  processor   : 1 vendor_id   : GenuineIntel cpu family  : 6 model       : 94 model name  : Intel(R) Core(TM) i7-6700 CPU @ 3.40GHz stepping    : 3 microcode   : 0xcc cpu MHz     : 800.005 cache size  : 8192 KB physical id : 0 siblings    : 4 core id     : 1 cpu cores   : 4 apicid      : 2 initial apicid  : 2 fpu     : yes fpu_exception   : yes cpuid level : 22 wp      : yes 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 nonstop_tsc cpuid aperfmperf tsc_known_freq pni pclmulqdq dtes64 monitor ds_cpl vmx smx est tm2 ssse3 sdbg fma cx16 xtpr pdcm pcid sse4_1 sse4_2 x2apic movbe popcnt tsc_deadline_timer aes xsave avx f16c rdrand lahf_lm abm 3dnowprefetch cpuid_fault invpcid_single pti ssbd ibrs ibpb stibp tpr_shadow vnmi flexpriority ept vpid fsgsbase tsc_adjust bmi1 hle avx2 smep bmi2 erms invpcid rtm 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 bugs        : cpu_meltdown spectre_v1 spectre_v2 spec_store_bypass l1tf mds bogomips    : 6816.00 clflush size    : 64 cache_alignment : 64 address sizes   : 39 bits physical, 48 bits virtual power management:  processor   : 2 vendor_id   : GenuineIntel cpu family  : 6 model       : 94 model name  : Intel(R) Core(TM) i7-6700 CPU @ 3.40GHz stepping    : 3 microcode   : 0xcc cpu MHz     : 799.997 cache size  : 8192 KB physical id : 0 siblings    : 4 core id     : 2 cpu cores   : 4 apicid      : 4 initial apicid  : 4 fpu     : yes fpu_exception   : yes cpuid level : 22 wp      : yes 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 nonstop_tsc cpuid aperfmperf tsc_known_freq pni pclmulqdq dtes64 monitor ds_cpl vmx smx est tm2 ssse3 sdbg fma cx16 xtpr pdcm pcid sse4_1 sse4_2 x2apic movbe popcnt tsc_deadline_timer aes xsave avx f16c rdrand lahf_lm abm 3dnowprefetch cpuid_fault invpcid_single pti ssbd ibrs ibpb stibp tpr_shadow vnmi flexpriority ept vpid fsgsbase tsc_adjust bmi1 hle avx2 smep bmi2 erms invpcid rtm 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 bugs        : cpu_meltdown spectre_v1 spectre_v2 spec_store_bypass l1tf mds bogomips    : 6816.00 clflush size    : 64 cache_alignment : 64 address sizes   : 39 bits physical, 48 bits virtual power management:  processor   : 3 vendor_id   : GenuineIntel cpu family  : 6 model       : 94 model name  : Intel(R) Core(TM) i7-6700 CPU @ 3.40GHz stepping    : 3 microcode   : 0xcc cpu MHz     : 800.000 cache size  : 8192 KB physical id : 0 siblings    : 4 core id     : 3 cpu cores   : 4 apicid      : 6 initial apicid  : 6 fpu     : yes fpu_exception   : yes cpuid level : 22 wp      : yes 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 nonstop_tsc cpuid aperfmperf tsc_known_freq pni pclmulqdq dtes64 monitor ds_cpl vmx smx est tm2 ssse3 sdbg fma cx16 xtpr pdcm pcid sse4_1 sse4_2 x2apic movbe popcnt tsc_deadline_timer aes xsave avx f16c rdrand lahf_lm abm 3dnowprefetch cpuid_fault invpcid_single pti ssbd ibrs ibpb stibp tpr_shadow vnmi flexpriority ept vpid fsgsbase tsc_adjust bmi1 hle avx2 smep bmi2 erms invpcid rtm 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 bugs        : cpu_meltdown spectre_v1 spectre_v2 spec_store_bypass l1tf mds bogomips    : 6816.00 clflush size    : 64 cache_alignment : 64 address sizes   : 39 bits physical, 48 bits virtual power management: