id summary reporter owner description type status component version resolution keywords cc guest host 19245 Nested virtualization greyed out with 6.1 (macOS, Broadwell) bcandler "I upgraded to Virtualbox 6.1.2 in order to try the new Nested Virtualization support. However, under Settings > System > Processor, the ""Enabled Nested VT-x/AMD-V"" button is greyed out. The machine is a retina MacBook Pro 13"", Early 2015 (MacBookPro12,1). It has a Broadwell CPU, i7-5557U. I can confirm that the VMX flag is present: {{{ $ sysctl -a | grep machdep.cpu.features machdep.cpu.features: FPU VME DE PSE TSC MSR PAE MCE CX8 APIC SEP MTRR PGE MCA CMOV PAT PSE36 CLFSH DS ACPI MMX FXSR SSE SSE2 SS HTT TM PBE SSE3 PCLMULQDQ DTES64 MON DSCPL VMX EST TM2 SSSE3 FMA CX16 TPR PDCM SSE4.1 SSE4.2 x2APIC MOVBE POPCNT AES PCID XSAVE OSXSAVE SEGLIM64 TSCTMR AVX1.0 RDRAND F16C }}} Looking in the manual: https://www.virtualbox.org/manual/ch09.html#nested-virt the following command was accepted without complaint: {{{ $ VBoxManage modifyvm ""ubuntu 18.04"" --nested-hw-virt on }}} and after this, the checkbox was both checked and not greyed. But after uncheck and save, it became greyed out again. Using the same command to enable nested-hw-virt again, I started the guest VM and /dev/kvm was present - meaning that nested virt is being presented to the guest - and I was able to run kvm successfully: {{{ $ kvm -m 512M -display vnc=0.0.0.0:0 -serial mon:stdio -cdrom TinyCore-current.iso qemu-system-x86_64: warning: host doesn't support requested feature: CPUID.80000001H:ECX.svm [bit 2] ... I was able to VNC connect to x.x.x.x:5900 to see the display ... }}} It seems that the problem is only with the greying out of the box, and not with being unable to run nested virt on this platform." defect closed GUI VirtualBox 6.1.2 invalid nested vt-x Linux Mac OS X