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    SubjectRe: perf hw in kexeced kernel broken in tip
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    On Wed, 2010-12-08 at 11:05 -0800, Yinghai Lu wrote:
    > On 12/08/2010 11:01 AM, Don Zickus wrote:
    > > On Wed, Dec 08, 2010 at 10:43:14AM -0800, Yinghai Lu wrote:
    > >>
    > >> can you add sth force_... in command line to take over ownership of perf from BIOS or previous kernel ?
    > >>
    > >> then still can use perf etc after we kexec from RHEL or SLES kernel to later kernel ( from 2.6.37)
    > >
    > > My understand is that you can't because the BIOS is actively using it
    > > behind the scenes of the kernel (well during an SMI). I have a machine
    > > where I tried to force take it but it still stopped triggering interrupts.
    >
    > how about second case: kexec from RHEL 6 stock kernel to upstream kernel ?

    Its impossible to distinguish between a BIOS having claimed a counter
    and a previous kernel not having shut things down properly.

    The best we can do is allow a force parameter and let the user keep all
    pieces when he uses it.


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