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Date: Thu, 25 Oct 2012 10:17:27 +0300
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Subject: Re: [BUG] lkvm crash on crashkernel boot
From: Pekka Enberg <penberg@kernel.org>
To: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Sasha Levin <levinsasha928@gmail.com>, Asias He <asias.hejun@gmail.com>,
        kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
        Cyrill Gorcunov <gorcunov@openvz.org>, Ingo Molnar <mingo@kernel.org>
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On Wed, Oct 24, 2012 at 6:27 PM, Kirill A. Shutemov
<kirill.shutemov@linux.intel.com> wrote:
> Hi,
>
> I've tried to play with kexec using lkvm. Unfortunately, lkvm crashes when
> I try to switch to crashkernel.
>
> I use Linus tree + penberg/kvmtool/next + one x86 mm patch[1].
>
> Kernel is defconfig + kvmconfig. I use the same kernel image for system and
> crash env.
>
> Host:
>
> % lkvm run --cpus 1 -m 1024 --params 'crashkernel=256M loglevel=8'
>
> Guest:
>
> # kexec -p bzImage --reuse-cmdline
> # echo c > /proc/sysrq-trigger
> ...
> [    0.947984] loop: module loaded
> [    0.950078] virtio-pci 0000:00:01.0: irq 40 for MSI/MSI-X
> [    0.950925] virtio-pci 0000:00:01.0: irq 41 for MSI/MSI-X
> [    0.952944] virtio-pci 0000:00:01.0: irq 42 for MSI/MSI-X
> zsh: segmentation fault (core dumped)  lkvm run --cpus 1 -m 1024 --params 'crashkernel=256M loglevel=8'

This seems to work OK on my machine.

> Guest kernel is somewhere in virtio_net initialization (for the second
> time). I'm too lazy to find exact line.
>
> Backtrace:
>
> 0  irq__add_msix_route (kvm=kvm@entry=0xbf8010, msg=0xe3d090) at x86/irq.c:210
> #1  0x000000000041b3bf in virtio_pci__specific_io_out.isra.5 (offset=<optimized out>,
>     data=<optimized out>, kvm=0xbf8010) at virtio/pci.c:150
> #2  virtio_pci__io_out.9406 (ioport=<optimized out>, kvm=0xbf8010, port=<optimized out>,
>     data=<optimized out>, size=<optimized out>) at virtio/pci.c:208
> #3  0x000000000040f8c3 in kvm__emulate_io (count=<optimized out>, size=2, direction=1,
>     data=<optimized out>, port=25108, kvm=0xbf8010) at ioport.c:165
> #4  kvm_cpu__start (cpu=<optimized out>) at x86/include/kvm/kvm-cpu-arch.h:41
> #5  0x0000000000416ca2 in kvm_cpu_thread.2824 (arg=<optimized out>) at builtin-run.c:176
> #6  0x00007f701ebd0b50 in start_thread (arg=<optimized out>) at pthread_create.c:304
> #7  0x00007f701e1fe70d in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:112
> #8  0x0000000000000000 in ?? ()

Looks like vpci->msix_table might not be initialized properly. Sasha,
Asias, care to take a look at this?

                        Pekka
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