My setup:
I see in VBox.log:
00:00:08.192929 HM: HMR3Init: Attempting fall back to NEM: VT-x is not available
What could cause this issue?
My diagnosis so far:
Background: NEM stands for Native Execution Mode. It is a fallback mode used by VirtualBox when VT-x (Intel Virtualization Technology) or AMD-V (AMD Virtualization) cannot be enabled due to system restrictions.
The issue is typically due to Hyper-V or some Windows security features.
I did these steps partly based on this virtualbox.org post:
Disabled that Hyper-V service:
Ran in cmd as admin:
bcdedit /set hypervisorlaunchtype off
Disabled that policy:
Disables all core isolation features:
Rebooted the laptop.
Then it worked: VBox.log show it's using VT-x now instead of NEM.
00:00:06.534552 HM: HMR3Init: VT-x w/ nested paging and unrestricted guest execution hw support
00:00:07.822064 HM: Using VT-x implementation 3.0
00:00:07.822121 HM: VT-x/AMD-V init method: Local
[...]
00:00:07.822532 *********************** VT-x features ***********************
00:00:07.822533 Nested hardware virtualization - VMX features
00:00:07.822534 Mnemonic - Description = guest (host)
00:00:07.822534 VMX - Virtual-Machine Extensions = 1 (1)
00:00:07.822534 InsOutInfo - INS/OUTS instruction info. = 1 (1)
00:00:07.822535 ExtIntExit - External interrupt exiting = 1 (1)
00:00:07.822535 NmiExit - NMI exiting = 1 (1)
00:00:07.822535 VirtNmi - Virtual NMIs = 1 (1)
00:00:07.822535 PreemptTimer - VMX preemption timer = 0 (1)
00:00:07.822536 PostedInt - Posted interrupts = 0 (1)
00:00:07.822536 IntWindowExit - Interrupt-window exiting = 1 (1)
00:00:07.822536 TscOffsetting - TSC offsetting = 1 (1)
00:00:07.822537 HltExit - HLT exiting = 1 (1)
00:00:07.822537 InvlpgExit - INVLPG exiting = 1 (1)
00:00:07.822537 MwaitExit - MWAIT exiting = 1 (1)
00:00:07.822537 RdpmcExit - RDPMC exiting = 1 (1)
00:00:07.822538 RdtscExit - RDTSC exiting = 1 (1)
00:00:07.822538 Cr3LoadExit - CR3-load exiting = 1 (1)
00:00:07.822538 Cr3StoreExit - CR3-store exiting = 1 (1)
00:00:07.822538 TertiaryExecCtls - Activate tertiary controls = 0 (1)
00:00:07.822539 Cr8LoadExit - CR8-load exiting = 1 (1)
00:00:07.822539 Cr8StoreExit - CR8-store exiting = 1 (1)
00:00:07.822539 UseTprShadow - Use TPR shadow = 1 (1)
00:00:07.822540 NmiWindowExit - NMI-window exiting = 1 (1)
00:00:07.822540 MovDRxExit - Mov-DR exiting = 1 (1)
00:00:07.822540 UncondIoExit - Unconditional I/O exiting = 1 (1)
00:00:07.822540 UseIoBitmaps - Use I/O bitmaps = 1 (1)
00:00:07.822541 MonitorTrapFlag - Monitor Trap Flag = 0 (1)
00:00:07.822541 UseMsrBitmaps - MSR bitmaps = 1 (1)
00:00:07.822541 MonitorExit - MONITOR exiting = 1 (1)
00:00:07.822541 PauseExit - PAUSE exiting = 1 (1)
00:00:07.822542 SecondaryExecCtl - Activate secondary controls = 1 (1)
00:00:07.822542 VirtApic - Virtualize-APIC accesses = 1 (1)
00:00:07.822542 Ept - Extended Page Tables = 1 (1)
00:00:07.822542 DescTableExit - Descriptor-table exiting = 1 (1)
00:00:07.822543 Rdtscp - Enable RDTSCP = 1 (1)
00:00:07.822543 VirtX2ApicMode - Virtualize-x2APIC mode = 0 (1)
00:00:07.822543 Vpid - Enable VPID = 1 (1)
00:00:07.822544 WbinvdExit - WBINVD exiting = 1 (1)
00:00:07.822544 UnrestrictedGuest - Unrestricted guest = 1 (1)
00:00:07.822544 ApicRegVirt - APIC-register virtualization = 0 (1)
00:00:07.822544 VirtIntDelivery - Virtual-interrupt delivery = 0 (1)
00:00:07.822545 PauseLoopExit - PAUSE-loop exiting = 1 (1)
00:00:07.822545 RdrandExit - RDRAND exiting = 1 (1)
00:00:07.822545 Invpcid - Enable INVPCID = 1 (1)
00:00:07.822545 VmFuncs - Enable VM Functions = 0 (1)
00:00:07.822546 VmcsShadowing - VMCS shadowing = 0 (0)
00:00:07.822546 RdseedExiting - RDSEED exiting = 1 (1)
00:00:07.822546 PML - Page-Modification Log = 0 (1)
00:00:07.822546 EptVe - EPT violations can cause #VE = 0 (1)
00:00:07.822547 ConcealVmxFromPt - Conceal VMX from Processor Trace = 0 (1)
00:00:07.822547 XsavesXRstors - Enable XSAVES/XRSTORS = 0 (1)
00:00:07.822547 PasidTranslate - PASID translation = 0 (0)
00:00:07.822548 ModeBasedExecuteEpt - Mode-based execute permissions = 0 (1)
00:00:07.822548 SppEpt - Sub-page page write permissions for EPT = 0 (0)
00:00:07.822548 PtEpt - Processor Trace address' translatable by EPT = 0 (1)
00:00:07.822548 UseTscScaling - Use TSC scaling = 0 (1)
00:00:07.822549 UserWaitPause - Enable TPAUSE, UMONITOR and UMWAIT = 0 (0)
00:00:07.822549 Pconfig - Enable PCONFIG = 0 (0)
00:00:07.822549 EnclvExit - ENCLV exiting = 0 (0)
00:00:07.822550 BusLockDetect - VMM Bus-Lock detection = 0 (0)
00:00:07.822551 InstrTimeout - Instruction timeout = 0 (0)
00:00:07.822551 LoadIwKeyExit - LOADIWKEY exiting = 0 (1)
00:00:07.822551 HLAT - Hypervisor-managed linear-address translation = 0 (0)
00:00:07.822552 EptPagingWrite - EPT paging-write = 0 (0)
00:00:07.822552 GstPagingVerify - Guest-paging verification = 0 (0)
00:00:07.822552 IpiVirt - IPI virtualization = 0 (0)
00:00:07.822552 VirtSpecCtrl - Virtualize IA32_SPEC_CTRL = 0 (0)
00:00:07.822553 EntryLoadDebugCtls - Load debug controls on VM-entry = 1 (1)
00:00:07.822553 Ia32eModeGuest - IA-32e mode guest = 1 (1)
00:00:07.822553 EntryLoadEferMsr - Load IA32_EFER MSR on VM-entry = 1 (1)
00:00:07.822553 EntryLoadPatMsr - Load IA32_PAT MSR on VM-entry = 1 (1)
00:00:07.822554 ExitSaveDebugCtls - Save debug controls on VM-exit = 1 (1)
00:00:07.822554 HostAddrSpaceSize - Host address-space size = 1 (1)
00:00:07.822554 ExitAckExtInt - Acknowledge interrupt on VM-exit = 1 (1)
00:00:07.822555 ExitSavePatMsr - Save IA32_PAT MSR on VM-exit = 1 (1)
00:00:07.822555 ExitLoadPatMsr - Load IA32_PAT MSR on VM-exit = 1 (1)
00:00:07.822555 ExitSaveEferMsr - Save IA32_EFER MSR on VM-exit = 1 (1)
00:00:07.822555 ExitLoadEferMsr - Load IA32_EFER MSR on VM-exit = 1 (1)
00:00:07.822556 SavePreemptTimer - Save VMX-preemption timer = 0 (1)
00:00:07.822556 SecondaryExitCtls - Secondary VM-exit controls = 0 (0)
00:00:07.822556 ExitSaveEferLma - Save IA32_EFER.LMA on VM-exit = 1 (1)
00:00:07.822556 IntelPt - Intel Processor Trace in VMX operation = 0 (1)
00:00:07.822557 VmwriteAll - VMWRITE to any supported VMCS field = 0 (1)
00:00:07.822557 EntryInjectSoftInt - Inject softint. with 0-len instr. = 1 (1)
00:00:07.822557
00:00:07.822557 ******************* End of VT-x features ********************
Note that it's likely that a subset of these instructions suffices to make it work.