[Qemu-devel] [Bug 682360] [NEW] Unaccessible memory

[JKB]

Public bug reported:

Hello,

I'm trying to develop a OS over L4/X2 microkernel and I use Linux debian
and qemu 0.13 in 64 bits mode. When I start qemu with qemu-system-x86_64
-hdc freevms.img -smp 1 -serial stdio -m 128M -k fr, my kernel boots
fine. If I modify this command line with -m 384M (for example), my
kernel is loaded but enter in a deadlock. I have found a bug in my code
until I have tried to use the _same_ disk image under virtualbox and it
works without any trouble. I runs fine on a real PC also.

I have bissected my code and qemu stops (maybe in a deadlock) when I try to 
access to memory :
%MEM-I-VM_ALLOC, adding $0000000000045000 - $0000000000108FFF to VM allocator
%MEM-I-VM_ALLOC, adding $000000000010B000 - $00000000003F2FFF to VM allocator
%MEM-I-VM_ALLOC, adding $000000000040C000 - $0000000000FFFFFF to VM allocator
%MEM-I-VM_ALLOC, adding $000000000100F000 - $FFFFFEFFFFFFFFFF to VM allocator
%MEM-I-ACCMAP, accepting mapping
%MEM-I-ACCMAP, virtual  $FFFF000000000000 - $FFFF000000000FFF
%MEM-I-ACCMAP, physical $000000000009E000 - $000000000009EFFF

Note that qemu doesn't crash. It only stops. My virtual memory subsystem
maps $FFFF000000000000 in physical memory ($9E000). And when I try to
initialize this memory, qemu enters in deadlock.

A disk image to reproduce this bug is available at
http://www.systella.fr/~bertrand/freevms.img.bz2

Regards,

JKB

** Affects: qemu
     Importance: Undecided
         Status: New

-- 
Unaccessible memory
https://bugs.launchpad.net/bugs/682360
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Status in QEMU: New

Bug description:
Hello,

I'm trying to develop a OS over L4/X2 microkernel and I use Linux debian and 
qemu 0.13 in 64 bits mode. When I start qemu with qemu-system-x86_64 -hdc 
freevms.img -smp 1 -serial stdio -m 128M -k fr, my kernel boots fine. If I 
modify this command line with -m 384M (for example), my kernel is loaded but 
enter in a deadlock. I have found a bug in my code until I have tried to use 
the _same_ disk image under virtualbox and it works without any trouble. I runs 
fine on a real PC also.

I have bissected my code and qemu stops (maybe in a deadlock) when I try to 
access to memory :
%MEM-I-VM_ALLOC, adding $0000000000045000 - $0000000000108FFF to VM allocator
%MEM-I-VM_ALLOC, adding $000000000010B000 - $00000000003F2FFF to VM allocator
%MEM-I-VM_ALLOC, adding $000000000040C000 - $0000000000FFFFFF to VM allocator
%MEM-I-VM_ALLOC, adding $000000000100F000 - $FFFFFEFFFFFFFFFF to VM allocator
%MEM-I-ACCMAP, accepting mapping
%MEM-I-ACCMAP, virtual  $FFFF000000000000 - $FFFF000000000FFF
%MEM-I-ACCMAP, physical $000000000009E000 - $000000000009EFFF

Note that qemu doesn't crash. It only stops. My virtual memory subsystem maps 
$FFFF000000000000 in physical memory ($9E000). And when I try to initialize 
this memory, qemu enters in deadlock.

A disk image to reproduce this bug is available at 
http://www.systella.fr/~bertrand/freevms.img.bz2

Regards,

JKB