Re: [PATCH] Activate Virtualization On Demand v3

[Alexander Graf <agraf@suse.de>]

Avi Kivity wrote:
> Alexander Graf wrote:
>> X86 CPUs need to have some magic happening to enable the virtualization
>> extensions on them. This magic can result in unpleasant results for
>> users, like blocking other VMMs from working (vmx) or using invalid TLB
>> entries (svm).
>>
>> Currently KVM activates virtualization when the respective kernel module
>> is loaded. This blocks us from autoloading KVM modules without breaking
>> other VMMs.
>>
>> To circumvent this problem at least a bit, this patch introduces on
>> demand activation of virtualization. This means, that instead
>> virtualization is enabled on creation of the first virtual machine
>> and disabled on removal of the last one.
>>
>> So using this, KVM can be easily autoloaded, while keeping other
>> hypervisors usable.
>>
>> v2 adds returns to non-x86 hardware_enables and adds IA64 change
>> v3 changes:
>>   - use spin_lock instead of atomics
>>   - put locking to new functions hardware_{en,dis}able_all that get
>> called
>>     on VM creation/destruction
>>   - remove usage counter checks where not necessary
>>   - return -EINVAL for IA64 slot < 0 case
>>
>>   
>
> Is this v3 with all the latest changes?  it precedes some messages
> where you say you'll change things by about 40 minutes.

Yeah, my clock was off. Somehow I get host time drifts sometimes when
using KVM and my NTP client wasn't running. But maybe it's just me doing
something wrong.

> In any case, I'll defer applying until Eduardo's kdump/reboot changes
> go in, since they touch the same places, and Eduardo's changes are
> much harder to test.

I agree.
Apart from that, do I get an ACK for it, so I can at least put it into
our package and rest assured nothing obvious is wrong :-)?

Alex