[Qemu-devel] QEMU aborts since "kvm: support using KVM_MEM_READONLY flag for regions"

[Peter Wu <lekensteyn@gmail.com>]

Hi,

With the current git source (f10acc8b38d65a66ffa0588a036489d7fa6a593e),
`qemu-system-x86_64 -enable-kvm` fails to run with the following error:

    kvm_set_phys_mem: error unregistering overlapping slot: Invalid argument

After this message, qemu aborts. Reverting the following commit on top of
master makes the bug go away. Removing the `-enable-kvm` option also
allows QEMU to operate, but without KVM.

commit 235e8982ad393e5611cb892df54881c872eea9e1
Author: Jordan Justen <jordan.l.justen@intel.com>
Date:   Wed May 29 01:27:26 2013 -0700

    kvm: support using KVM_MEM_READONLY flag for regions
    
    For readonly memory regions and rom devices in romd_mode,
    we make use of the KVM_MEM_READONLY. A slot that uses
    KVM_MEM_READONLY can be read from and code can execute from the
    region, but writes will exit to qemu.
    
    For rom devices with !romd_mode, we force the slot to be
    removed so reads or writes to the region will exit to qemu.
    (Note that a memory region in this state is not executable
    within kvm.)

QEMU was built using GCC 4.8.0, runs on Arch Linux 64-bit with a
custom kernel, Linux 3.9.1. CPU: i5-460M. A backtrace is provided
on the bottom of this message. If you need more details, please ask.

Regards,
Peter

#0  0x00007ffff1a251c9 in raise () from /usr/lib/libc.so.6
#1  0x00007ffff1a265c8 in abort () from /usr/lib/libc.so.6
#2  0x00005555557dd84d in kvm_set_phys_mem (section=0x7fffe6fdca00, add=false) at /tmp/qemu/kvm-all.c:715
#3  0x00005555557e132c in address_space_update_topology_pass (as=as@entry=0x5555564dae00 <address_space_memory>, adding=adding@entry=false, old_view=..., new_view=...) at /tmp/qemu/memory.c:725
#4  0x00005555557e1f13 in address_space_update_topology (as=0x5555564dae00 <address_space_memory>) at /tmp/qemu/memory.c:761
#5  memory_region_transaction_commit () at /tmp/qemu/memory.c:786
#6  0x00005555557dfa42 in access_with_adjusted_size (addr=addr@entry=2, value=value@entry=0x7fffe6fdcc18, size=1, access_size_min=<optimized out>, access_size_max=<optimized out>, 
    access=access@entry=0x5555557e0000 <memory_region_write_accessor>, opaque=opaque@entry=0x55555658c238) at /tmp/qemu/memory.c:399
#7  0x00005555557e0f77 in memory_region_iorange_write (iorange=<optimized out>, offset=2, width=1, data=51) at /tmp/qemu/memory.c:475
#8  0x00005555557de562 in kvm_handle_io (count=1, size=1, direction=1, data=<optimized out>, port=3326) at /tmp/qemu/kvm-all.c:1507
#9  kvm_cpu_exec (env=env@entry=0x55555656f750) at /tmp/qemu/kvm-all.c:1659
#10 0x000055555578da05 in qemu_kvm_cpu_thread_fn (arg=0x55555656f750) at /tmp/qemu/cpus.c:759
#11 0x00007ffff6280dd2 in start_thread () from /usr/lib/libpthread.so.0
#12 0x00007ffff1ad5cdd in clone () from /usr/lib/libc.so.6