linux-kernel - [BUG] lkvm crash on crashkernel boot

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Message-ID: <20121024152740.GA25303@otc-wbsnb-06>
Date:	Wed, 24 Oct 2012 18:27:40 +0300
From:	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To:	Pekka Enberg <penberg@...nel.org>,
	Sasha Levin <levinsasha928@...il.com>,
	Asias He <asias.hejun@...il.com>
Cc:	kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [BUG] lkvm crash on crashkernel boot

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'

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@...ry=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 ?? ()

[1] https://patchwork.kernel.org/patch/1608411/

-- 
 Kirill A. Shutemov

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