Re: [Qemu-devel] 32-bit “qemu-system-i386 -enable-kvm” segfaults on x86_64

[Daniel P . Berrangé]

On Wed, Jul 04, 2018 at 02:34:07PM +0200, Ludovic Courtès wrote:
> Hello,
> 
> (I’m reporting the issue here because for some reason the launchpad.net
> login page redirects me to an “oops” page and fails to log me in.)
> 
> On a Linux 4.17 x86_64 host, “qemu-system-i386 -enable-kvm”, where
> qemu-system-i386 is a 32-bit binary, crashes (it works fine without
> ‘-enable-kvm’):
> 
> --8<---------------cut here---------------start------------->8---
> $ uname -rm
> 4.17.3-gnu x86_64
> $ file 
> /gnu/store/h22dc67wzkv0w2l3775f0xqkyr318x5j-qemu-minimal-2.12.0/bin/qemu-system-i386
>  
> /gnu/store/h22dc67wzkv0w2l3775f0xqkyr318x5j-qemu-minimal-2.12.0/bin/qemu-system-i386:
>  ELF 32-bit LSB shared object, Intel 80386, version 1 (SYSV), dynamically 
> linked, interpreter 
> /gnu/store/4aka3nwppxf3z072l6vr8cxvwj3x5h9s-glibc-2.27/lib/ld-linux.so.2, for 
> GNU/Linux 2.6.32, stripped

It appears that not only are you using qemu-system-i386 on x86_64
host, but this has actually also been built as a 32-bit ELF binary,
so will be using the 32-bit compat syscalls. This is quite possibly
relevant to any crash, so it would be useful to know if qemu-system-i386,
when built as a 64-bit ELF binary works or fails.

It appears you are using 2.12.0 release, so it is also helpful if
you would try using current git master to see if it still reproduces.


> $ 
> /gnu/store/h22dc67wzkv0w2l3775f0xqkyr318x5j-qemu-minimal-2.12.0/bin/qemu-system-i386
>  -enable-kvm /dev/null
> WARNING: Image format was not specified for '/dev/null' and probing guessed 
> raw.
>          Automatically detecting the format is dangerous for raw images, 
> write operations on block 0 will be restricted.
>          Specify the 'raw' format explicitly to remove the restrictions.
> VNC server running on 127.0.0.1:5900
> Adres-eraro(nekropsio elŝutita)
> --8<---------------cut here---------------start------------->8---
> 
> I’d need debugging symbols to provide a useful backtrace, but perhaps
> the strace gives useful hints:

strace's are fairly unhelpful I'm afraid, so collecting a stack trace
would be best next step.

Regards,
Daniel
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