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    SubjectRe: KVM induced panic on 2.6.38[2367] & 2.6.39

    On Wed, Jun 01, 2011 at 08:37:25AM +0800, Brad Campbell wrote:
    > On 01/06/11 06:31, Hugh Dickins wrote:
    > > Brad, my suspicion is that in each case the top 16 bits of RDX have been
    > > mysteriously corrupted from ffff to 0000, causing the general protection
    > > faults. I don't understand what that has to do with KSM.
    > >
    > > But it's only a suspicion, because I can't make sense of the "Code:"
    > > lines in your traces, they have more than the expected 64 bytes, and
    > > only one of them has a ">" (with no"<") to mark faulting instruction.
    > >
    > > I did try compiling the 2.6.39 kernel from your config, but of course
    > > we have different compilers, so although I got close, it wasn't exact.
    > >
    > > Would you mind mailing me privately (it's about 73MB) the "objdump -trd"
    > > output for your original vmlinux (with KSM on)? (Those -trd options are
    > > the ones I'm used to typing, I bet not they're not all relevant.)
    > >
    > > Of course, it's only a tiny fraction of that output that I need,
    > > might be better to cut it down to remove_rmap_item_from_tree and
    > > dup_fd and ksm_scan_thread, if you have the time to do so.
    > Would you believe about 20 seconds after I pressed send the kernel oopsed.
    > oops reproduced here, but an un-munged version is in that directory
    > alongside the kernel.
    > [36542.880228] general protection fault: 0000 [#1] SMP

    Reminds me of another oops that was reported on the kvm list for with message id 4D8C6110.6090204. There the top 16 bits of
    rsi were flipped and it was a general protection too because of
    hitting on the not mappable virtual range.

    That oops happened in kvm_unmap_rmapp though, but it looked memory
    corruption (Avi suggested use after free) but it was a production
    system so we couldn't debug it further.

    I recommend next thing to reproduce again with 2.6.39 or
    3.0.0-rc1. Let's fix your scsi trouble if needed but it's better you
    test with 2.6.39.

    We'd need chmod +r vmlinux on private/003_kernel_oops/


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