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

[Peter Wu]

On Monday 03 June 2013 10:35:28 Jordan Justen wrote:
> This should be fixed by Xiao's "fix double free the memslot in
> kvm_set_phys_mem" patch.
Confirmed, with this one-liner patch the bug is gone.

> On Mon, Jun 3, 2013 at 10:23 AM, Peter Wu <address@hidden> wrote:
> > 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 <address@hidden>
> > 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 (address@hidden
> > <address_space_memory>, address@hidden, 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 (address@hidden,
> > address@hidden, size=1, access_size_min=<optimized
> > out>, access_size_max=<optimized out>,> 
> >     address@hidden <memory_region_write_accessor>,
> >     address@hidden) 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 (address@hidden) 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