Re: [patch] VMX Unrestricted mode support

Anthony Liguori
2009-05-31T15:23:10Z

Nitin A Kamble wrote:
> Avi,
>
> A new VMX feature "Unrestricted Guest" feature is added in the VMX
> specification. You can look at the latest Intel processor manual for
> details of the feature here:
>
> http://www.intel.com/products/processor/manuals
>
> It allows kvm guests to run real mode and unpaged mode
> code natively in the VMX mode when EPT is turned on. With the
> unrestricted guest there is no need to emulate the guest real mode code
> in the vm86 container or in the emulator. Also the guest big real mode
> code works like native.
>
> The attached patch enhances KVM to use the unrestricted guest feature
> if available on the processor. It also adds a new kernel/module
> parameter to disable the unrestricted guest feature at the boot time.
>
> Signed-Off-By: Nitin A Kamble <nitin.a.kamble@intel.com>
>
> Thanks & Regards,
> Nitin
>

It may make sense to expose this as a CAP down to userspace.

We could possibly make better error messages in userspace when we get an
unknown vmexit failure on pre-wsm hardware.

Regards,

Anthony Liguori