Footnotes and Experimental Spectre / Meltdown Defenses
Please press on expand on the right.
Testers only! For more information please press on expand on the right.
These experimental Spectre/Meltdown defenses are related to issues outlined in Firmware Security and Updates. Due to the huge performance penalty and unclear security benefits of applying these changes, it may not be worth the effort. The reason is VirtualBox is still likely vulnerable, even after:
- A host microcode upgrade.
- A host kernel upgrade.
- A VM kernel upgrade.
- A "not vulnerable" result from spectre-meltdown-checker run on the host.
- Installation of the latest VirtualBox version. 
- All Spectre/Meltdown-related VirtualBox settings are tuned for better security as documented below.
To learn more, see: VirtualBox 5.2.18 vulnerable to spectre/meltdown despite microcode being installed and the associated VirtualBox forum discussion.  Users must patiently wait for VirtualBox developers to fix this bug.
VBoxManage modifyvm "Whonix-Gateway" --ibpb-on-vm-entry on
VBoxManage modifyvm "Whonix-Workstation" --ibpb-on-vm-entry on
VBoxManage modifyvm "Whonix-Gateway" --ibpb-on-vm-exit on
VBoxManage modifyvm "Whonix-Workstation" --ibpb-on-vm-exit on
VBoxManage modifyvm "Whonix-Gateway" --l1d-flush-on-vm-entry on
VBoxManage modifyvm "Whonix-Workstation" --l1d-flush-on-vm-entry on
VBoxManage modifyvm "Whonix-Gateway" --l1d-flush-on-sched on
VBoxManage modifyvm "Whonix-Workstation" --l1d-flush-on-sched on
VBoxManage modifyvm "Whonix-Gateway" --spec-ctrl on
VBoxManage modifyvm "Whonix-Workstation" --spec-ctrl on
VBoxManage modifyvm "Whonix-Gateway" --nestedpaging off
VBoxManage modifyvm "Whonix-Workstation" --nestedpaging off
The above instructions only apply to the default VM names Whonix-Gateway ™ and Whonix-Workstation ™. Therefore, if Multiple Whonix-Workstation ™s and/or Multiple Whonix-Gateway ™s are configured, then repeat these instructions using the relevant name/s.
5.2.18or above is required since only that version comes with Spectre/Meltdown defenses. See https://forums.whonix.org/t/whonix-vulerable-due-to-missing-processor-microcode-packages/5739/22.
- Also see the following Whonix forum discussion: Whonix vulerable due to missing processor microcode packages? spectre / meltdown / retpoline / L1 Terminal Fault (L1TF)
--ibpb-on-vm-[enter|exit] on|off: Enables flushing of the indirect branch prediction buffers on every VM enter or exit respectively. This could be enabled by users overly worried about possible spectre attacks by the VM. Please note that these options may have sever impact on performance.
There is a mistake in the VirtualBox manual stating
enterwhich does not work. It is actually
--l1d-flush-on-vm-enter on|off: Enables flushing of the level 1 data cache on VM enter. See Section 13.4.1, “CVE-2018-3646”.
For users not concerned by this security issue, the default mitigation can be disabled using
VBoxManage modifyvm name --l1d-flush-on-sched off
Since we want to enable the security feature we set
--spec-ctrl on|off: This setting enables/disables exposing speculation control interfaces to the guest, provided they are available on the host. Depending on the host CPU and workload, enabling speculation control may significantly reduce performance.
According to this VirtualBox ticket
--spec-ctrlshould be set to
--nestedpaging on|off: If hardware virtualization is enabled, this additional setting enables or disables the use of the nested paging feature in the processor of your host system; see Section 10.7, “Nested paging and VPIDs” and Section 13.4.1, “CVE-2018-3646”.
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