On Fri, Mar 4, 2011 at 12:04 PM, Derek Simkowiak <der...@realloc.net> wrote:
> There are no downsides I am aware of. It just lets run VMs run much > faster than without it. > > I don't know why they made it a BIOS option, rather than 'always on'. > > The processor reports the capability to the BIOS via the CPUID instruction and it must be enabled prior to use by an OS/hypervisor. The BIOS is given the responsibility of enabling it after checking if the processor actually supports it. The on/off switch in the BIOS is just like all the other knobs and settings the BIOS has control over. If your processor supports EPT (exteneded page tables, AMD calls it NP or nested paging or similar) I suggest enabling VT in the BIOS and EPT in VirtualBox. This allows the virtual machine to handle its own paging without the need for help from the hypervisor. This addresses one of the large bottlenecks when running a virtual machine, the other being direct access to the I/O devices, which is addressed by VT-d. -- Jeff Speaking for myself, not my employer.
