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    SubjectRe: [RFC] Unify KVM kernel-space and user-space code into a single project

    * Avi Kivity <> wrote:

    > On 03/21/2010 10:08 PM, Olivier Galibert wrote:
    > >On Sun, Mar 21, 2010 at 10:01:51PM +0200, Avi Kivity wrote:
    > >>On 03/21/2010 09:17 PM, Ingo Molnar wrote:
    > >>>Adding any new daemon to an existing guest is a deployment and usability
    > >>>nightmare.
    > >>>
    > >>The logical conclusion of that is that everything should be built into
    > >>the kernel. Where a failure brings the system down or worse. Where you
    > >>have to bear the memory footprint whether you ever use the functionality
    > >>or not. Where to update the functionality you need to deploy a new
    > >>kernel (possibly introducing unrelated bugs) and reboot.
    > >>
    > >>If userspace daemons are such a deployment and usability nightmare,
    > >>maybe we should fix that instead.
    > >Which userspace? Deploying *anything* in the guest can be a
    > >nightmare, including paravirt drivers if you don't have a natively
    > >supported in the OS virtual hardware backoff.
    > That includes the guest kernel. If you can deploy a new kernel in the
    > guest, presumably you can deploy a userspace package.

    Note that with perf we can instrument the guest with zero guest-kernel
    modifications as well.

    We try to reduce the guest impact to a bare minimum, as the difficulties in
    deployment are function of the cross section surface to the guest.

    Also, note that the kernel is special with regards to instrumentation: since
    this is the kernel project, we are doing kernel space changes, as we are doing
    them _anyway_. So adding symbol resolution capabilities would be a minimal
    addition to that - while adding a while new guest package for the demon would
    significantly increase the cross section surface.


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