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    SubjectRe: vsyscall=emulate regression
    Hi,

    On (Fri) 03 Feb 2012 [07:30:55], Andy Lutomirski wrote:
    > On Fri, Feb 3, 2012 at 12:27 AM, Amit Shah <amit.shah@redhat.com> wrote:
    > > Hello,
    > >
    > > I'm booting some latest kernels on a Fedora 11 (released June 2009)
    > > guest.  After the recent change of default to vsyscall=emulate, the
    > > guest fails to boot (init segfaults).
    >
    > Which kernel is the host running

    Host is a RHEL6 kernel, 2.6.32-217.el6.x86_64

    > and which kernel is the guest
    > running? And which kernel has the vsyscall=emulate parameter?

    The host stays the same; I'm only using the x86-64 F11 guest with
    newer kernel versions. I compile the kernels on the host, and use
    qemu's -kernel parameter so the guest boots off that kernel.

    Only the guest gets the vsyscall= parameters.

    > If
    > vsyscall=emulate is a problem on a pre-3.3 kernel, can you try
    > something containing commit 4fc3490114bb159bd4fff1b3c96f4320fe6fb08f?
    > (UML, for example, is known to have serious issues without that fix.)

    I've tried all kernels v3.0 to v3.3-git. From the commit that
    introduced the vsyscall=emulate parameter, using 'emulate' has failed
    to boot this guest. I only noticed it recently when it was made the
    default.

    > Otherwise, can you tell me what hypervisor you're using

    Sorry, I'm using kvm. qemu is also from RHEL6,
    qemu-kvm-0.12.1.2-2.209.el6.x86_64, but even upstream qemu.git makes
    init fail similarly.

    > and what init
    > version (i.e. the rpm) so I can try to reproduce it?

    upstart-0.6.5-10.el6.x86_64

    > A pointer to an
    > actual image would work, too.

    It's mostly a stock F11 install, so fetching the iso and installing it
    locally, and using a command line similar to:

    qemu-kvm -snapshot -kernel ~/src/linux/arch/x86/boot/bzImage
    /guests/f11-auto.qcow2 -serial stdio -append 'console=tty0
    console=ttyS0 root=/dev/sda2 vsyscall=emulate'

    will work.

    > A copy of the oops would also be nice.

    There's not much, but here it is anyway:

    EXT4-fs (sda2): couldn't mount as ext3 due to feature incompatibilities
    EXT4-fs (sda2): couldn't mount as ext2 due to feature incompatibilities
    EXT4-fs (sda2): mounted filesystem with ordered data mode. Opts: (null)
    VFS: Mounted root (ext4 filesystem) readonly on device 8:2.
    debug: unmapping init memory ffffffff8167f000..ffffffff818e1000
    Write protecting the kernel read-only data: 6144k
    debug: unmapping init memory ffff8800012fe000..ffff880001400000
    debug: unmapping init memory ffff880001584000..ffff880001600000
    init[1]: segfault at ffffffffff600400 ip ffffffffff600400 sp 00007fff103d72f8 error 5
    Kernel panic - not syncing: Attempted to kill init!


    That's with current git snapshot. With the commit that introduced
    vsyscal= I had gotten this:

    EXT4-fs (sda2): couldn't mount as ext3 due to feature incompatibilities
    EXT4-fs (sda2): couldn't mount as ext2 due to feature incompatibilities
    EXT4-fs (sda2): mounted filesystem with ordered data mode. Opts: (null)
    VFS: Mounted root (ext4 filesystem) readonly on device 8:2.
    debug: unmapping init memory ffffffff81679000..ffffffff818db000
    Write protecting the kernel read-only data: 6144k
    debug: unmapping init memory ffff8800012e6000..ffff880001400000
    debug: unmapping init memory ffff880001579000..ffff880001600000
    init[1]: segfault at ffffffffff600400 ip ffffffffff600400 sp 00007fff9c8ba098 error 5
    Kernel panic - not syncing: Attempted to kill init!
    Pid: 1, comm: init Not tainted 3.0.0+ #189
    Call Trace:
    [<ffffffff812de4e9>] panic+0x9b/0x1a2
    [<ffffffff8102ba99>] ? get_parent_ip+0x11/0x41
    [<ffffffff81039ff6>] do_exit+0xb0/0x6f0
    [<ffffffff8103a6bf>] do_group_exit+0x89/0xb7
    [<ffffffff81048ffa>] get_signal_to_deliver+0x419/0x438
    [<ffffffff810016dd>] do_signal+0x72/0x5e4
    [<ffffffff8101e827>] ? do_page_fault+0x177/0x338
    [<ffffffff812de631>] ? printk+0x41/0x48
    [<ffffffff810dd93d>] ? discard_slab+0x3e/0x40
    [<ffffffff810dea12>] ? __slab_free+0x13a/0x145
    [<ffffffff810ef4fd>] ? putname+0x32/0x3b
    [<ffffffff810ef4fd>] ? putname+0x32/0x3b
    [<ffffffff810df179>] ? kmem_cache_free+0x7d/0xce
    [<ffffffff812e1adf>] ? retint_signal+0x11/0x92
    [<ffffffff81001c69>] do_notify_resume+0x1a/0x37
    [<ffffffff812e1b1b>] retint_signal+0x4d/0x92


    Amit
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