Re: [PATCH] Activate Virtualization On Demand v3

[Avi Kivity <avi@redhat.com>]

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.

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.

-- 
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