Re: [PATCH] Activate Virtualization On Demand v2

[Alexander Graf <agraf@suse.de>]

Daniel P. Berrange wrote:
> On Wed, Nov 05, 2008 at 09:48:16AM +0100, 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.
>>     
>
> Pardon my unfamiliarity with the code, but with this change applied,
> will we still get an explicit error at time of loading kvm-intel.ko
> if VMX were disabled in the BIOS ? Or will that error reporting be 
> pushed off to time when VMX is first activated ?
>   

The BIOS and hardware support checks are in kvm_arch_init, which is
still called at load-time of the module.

Alex