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    SubjectRe: [RFC] Unify KVM kernel-space and user-space code into a single project
    Avi Kivity wrote:
    > On 03/24/2010 02:50 PM, Joerg Roedel wrote:
    >>> You can always provide the kernel and module paths as command line
    >>> parameters. It just won't be transparently usable, but if you're using
    >>> qemu from the command line, presumably you can live with that.
    >> I don't want the tool for myself only. A typical perf user expects that
    >> it works transparent.
    > A typical kvm user uses libvirt, so we can integrate it with that.
    >>>> Could be easily done using notifier chains already in the kernel.
    >>>> Probably implemented with much less than 100 lines of additional code.
    >>> And a userspace interface for that.
    >> Not necessarily. The perf event is configured to measure systemwide kvm
    >> by userspace. The kernel side of perf takes care that it stays
    >> system-wide even with added vm instances. So in this case the consumer
    >> for the notifier would be the perf kernel part. No userspace interface
    >> required.
    > Someone needs to know about the new guest to fetch its symbols. Or do
    > you want that part in the kernel too?

    How about we add a virtio "guest file system access" device? The guest
    would then expose its own file system using that device.

    On the host side this would simply be a -virtioguestfs
    unix:/tmp/guest.fs and you'd get a unix socket that gives you full
    access to the guest file system by using commands. I envision something

    SEND: GET /proc/version
    RECV: Linux version (geeko@buildhost) (gcc version
    4.3.2 [gcc-4_3-branch revision 141291] (SUSE Linux) ) #1 SMP 2009-10-15
    14:56:58 +0200

    Now all we need is integration in perf to enumerate virtual machines
    based on libvirt. If you want to run qemu-kvm directly, just go with
    --guestfs=/tmp/guest.fs and perf could fetch all required information

    This should solve all issues while staying 100% in user space, right?


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