Re: [PATCH 00/10] Add support for nested SVM (kernel) v4

[Avi Kivity <avi@redhat.com>]

Alexander Graf wrote:
> The current generation of virtualization extensions only supports one VM layer.
> While we can't change that, it is pretty easy to emulate the CPU's behavior
> and implement the virtualization opcodes ourselves.
>
> This patchset does exactly this for SVM. Using it, KVM can run within a VM.
> Since we're emulating the real CPU's behavior, this should also enable other
> VMMs to run within KVM.
> So far I've only tested to run KVM inside the VM though.
>
> As always, comments and suggestions are highly welcome.
>
> v2 takes most comments from Avi into account.
>
> v3 addresses Joergs comments, including
>
> - V_INTR_MASKING support
> - a generic permission checking helper
>
> v4 addresses even more comments from Joerg, including
>
> - don't use the guest's hsave to store the guest's vmcb in
> - add nested=<int> flag for kvm-amd.ko, defaults to 0 (off)
> - include Joerg's VM_CR MSR patch
>
> To be usable, this patchset requires the two simple changes in the userspace
> part, that I sent to the list with the first version.
>
> Known issues:
>
> - TODO: #VMEXIT on save/restore
> - SMP l2 guests break with in-kernel-apic
>   

Looks ready to apply, though it would be good to get smp working.  
Defaulting to off relaxes some of the worries.

I assume the move to host-backed hsave fixes the security hole Joerg 
spotted?

-- 
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