Re: [PATCH 0/3] KVM: Make KVM_CHECK_EXTENSION a VM ioctl

[Paolo Bonzini <pbonzini@redhat.com>]

Il 14/07/2014 19:03, Alexander Graf ha scritto:
> On PowerPC we have a small problem :). We can run both HV and PR style VMs
> on the same kvm fd. While this is great, it means that anything that's
> different between the two needs to have a token in form of a VM fd to find
> out which one we're asking for.
>
> The one thing where this bites us are CAPs. We ask for them on the kvm fd,
> not the vm fd. So we can only take a random guess whether the user is asking
> for HV or PR capabilities.
>
> So far we got away with this reasonably well - most people will only load one
> of the two modules and the only thing that *really* breaks is hypercall exposure
> to user space, so a PR guest will not be able to do KVM hypercalls when HV KVM
> is loaded on the host, making the magic page unavailable to it.
>
> But this still isn't a great situation to be in. Instead, we really should just
> make the CHECK_EXTENSION ioctl available at VM level. Then we know for sure
> what user space is asking for.
>
>
> Alex
>
> Alexander Graf (3):
>   KVM: Rename and add argument to check_extension
>   KVM: Allow KVM_CHECK_EXTENSION on the vm fd
>   KVM: PPC: Book3S: Provide different CAPs based on HV or PR mode
>
>  Documentation/virtual/kvm/api.txt |  5 +++-
>  arch/arm/kvm/arm.c                |  2 +-
>  arch/ia64/kvm/kvm-ia64.c          |  2 +-
>  arch/mips/kvm/mips.c              |  2 +-
>  arch/powerpc/kvm/powerpc.c        | 14 +++++++---
>  arch/s390/kvm/kvm-s390.c          |  2 +-
>  arch/x86/kvm/x86.c                |  2 +-
>  include/linux/kvm_host.h          |  2 +-
>  virt/kvm/kvm_main.c               | 59 ++++++++++++++++++++-------------------
>  9 files changed, 51 insertions(+), 39 deletions(-)
>

Acked-by: Paolo Bonzini <pbonzini@redhat.com>

Feel free to include it in your pull request.

Paolo