Debian KVM Virtualization – Enabling Virtualization on Supermicro Board

I'm trying to setup a virtualization server on an old Supermicro board (mainly for experimenting a bit), using qemu/kvm (running on Debian/jessie, with a 3.16.0-4-amd64 kernel)

The board is equipped with Intel Xeon CPUs, and as I understand it they should support virtualisation:

$ egrep '^flags.*(vmx|svm)' /proc/cpuinfo
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 lm constant_tsc pebs bts nopl pni dtes64 monitor ds_cpl vmx est cid cx16 xtpr pdcm lahf_lm tpr_shadow
$

Regardless of the vmx flag being present, KVM refuses to initialize:

$ dmesg | grep kvm
[    8.721594] kvm: disabled by bios
$

The kvm-intel module cannot be loaded, and qemu falls back to emulation mode (which is really slow…)

So I rebooted the host, entered the BIOS and turned on virtualization in advanced CPU settings (it was indeed turned off).

Unfortunately, this didn't change a ι, and KVM still complains about being disabled in the BIOS.

Here's some details about my hardware (CPU/motherboard):

root:~# dmidecode -t2
# dmidecode 2.12
SMBIOS 2.4 present.

Handle 0x0002, DMI type 2, 8 bytes
Base Board Information
    Manufacturer: Supermicro
    Product Name: X7DB8
    Version: PCB Version
    Serial Number: 0123456789

root:~# lscpu 
Architecture:          x86_64
CPU op-mode(s):        32-bit, 64-bit
Byte Order:            Little Endian
CPU(s):                8
On-line CPU(s) list:   0-7
Thread(s) per core:    2
Core(s) per socket:    2
Socket(s):             2
NUMA node(s):          1
Vendor ID:             GenuineIntel
CPU family:            15
Model:                 6
Model name:            Intel(R) Xeon(TM) CPU 3.00GHz
Stepping:              4
CPU MHz:               3000.146
BogoMIPS:              6000.62
Virtualization:        VT-x
L1d cache:             16K
L2 cache:              2048K
NUMA node0 CPU(s):     0-7
root:~# cpuid -1
CPU:
   vendor_id = "GenuineIntel"
   version information (1/eax):
      processor type  = primary processor (0)
      family          = Intel Pentium 4/Pentium D/Pentium Extreme Edition/Celeron/Xeon/Xeon MP/Itanium2, AMD Athlon 64/Athlon XP-M/Opteron/Sempron/Turion (15)
      model           = 0x6 (6)
      stepping id     = 0x4 (4)
      extended family = 0x0 (0)
      extended model  = 0x0 (0)
      (simple synth)  = Intel Pentium 4 Processor 6x1 (Cedar Mill C1) / Pentium Extreme Edition Processor 955 (Presler C1) / Pentium D Processor 9xx (Presler C1) / Xeon Processor 5000 (Dempsey C1) / Celeron D Processor 3xx (Cedar Mill C1), 65nm
   miscellaneous (1/ebx):
      process local APIC physical ID = 0x1 (1)
      cpu count                      = 0x4 (4)
      CLFLUSH line size              = 0x8 (8)
      brand index                    = 0x0 (0)
   brand id = 0x00 (0): unknown
   feature information (1/edx):
      x87 FPU on chip                        = true
      virtual-8086 mode enhancement          = true
      debugging extensions                   = true
      page size extensions                   = true
      time stamp counter                     = true
      RDMSR and WRMSR support                = true
      physical address extensions            = true
      machine check exception                = true
      CMPXCHG8B inst.                        = true
      APIC on chip                           = true
      SYSENTER and SYSEXIT                   = true
      memory type range registers            = true
      PTE global bit                         = true
      machine check architecture             = true
      conditional move/compare instruction   = true
      page attribute table                   = true
      page size extension                    = true
      processor serial number                = false
      CLFLUSH instruction                    = true
      debug store                            = true
      thermal monitor and clock ctrl         = true
      MMX Technology                         = true
      FXSAVE/FXRSTOR                         = true
      SSE extensions                         = true
      SSE2 extensions                        = true
      self snoop                             = true
      hyper-threading / multi-core supported = true
      therm. monitor                         = true
      IA64                                   = false
      pending break event                    = true
   feature information (1/ecx):
      PNI/SSE3: Prescott New Instructions     = true
      PCLMULDQ instruction                    = false
      64-bit debug store                      = true
      MONITOR/MWAIT                           = true
      CPL-qualified debug store               = true
      VMX: virtual machine extensions         = true
      SMX: safer mode extensions              = false
      Enhanced Intel SpeedStep Technology     = true
      thermal monitor 2                       = false
      SSSE3 extensions                        = false
      context ID: adaptive or shared L1 data  = true
      FMA instruction                         = false
      CMPXCHG16B instruction                  = true
      xTPR disable                            = true
      perfmon and debug                       = true
      process context identifiers             = false
      direct cache access                     = false
      SSE4.1 extensions                       = false
      SSE4.2 extensions                       = false
      extended xAPIC support                  = false
      MOVBE instruction                       = false
      POPCNT instruction                      = false
      time stamp counter deadline             = false
      AES instruction                         = false
      XSAVE/XSTOR states                      = false
      OS-enabled XSAVE/XSTOR                  = false
      AVX: advanced vector extensions         = false
      F16C half-precision convert instruction = false
      RDRAND instruction                      = false
      hypervisor guest status                 = false
[...]
#

So my question is: does anybody know how to enable virtualization on that CPU/motherboard, or am I simply out of luck?