Re: VMX ideas

Alexander Graf
2008-11-03T07:32:35Z

Am 02.11.2008 um 11:28 schrieb Avi Kivity <avi@redhat.com>:

> Gerd Hoffmann wrote:
>>> 3. Create a root mode bloat framework
>>>
>>
>> 4. Enter vmx root mode when the first user opens /dev/kvm and leave
>> it
>> when nobody uses it any more?
>>
>> Also note that there has been some discussion on lkml to move vmx-
>> root
>> on/off out of the kvm module into the kernel. There are a few places
>> where it would be useful for the kernel to handle that without the
>> kvm
>> module being involved, crashdump kexec for example. With that and
>> some
>> locking in place (so only one can use vmx-root at a time) and
>> hypervisors being friendly to each other and grab vmx-root only when
>> they have a guest to run we should be set
>
> That means that although kvm is loaded it may be unable to service /
> dev/kvm... something I'd like to avoid.

This would happen even with a vmx framework in place - unless we
really always activate root mode, which would break 32-bit vmware/vbox.

The way I have it implemented atm, root mode is activated on first
usage. If kvm happens to be blocked out of using vmx due to various
reasons, create_vcpu would fail. What exactly is bad about this?

And even if we were to always activate root mode, a vmx user that
needs exclusive access (e.g. uses vpids) could still block kvm.

Alex

>
>
> --
> error compiling committee.c: too many arguments to function
>