Re: [PATCH v2 1/1] Fix the coredump when memory backend id conflicts with default_ram_id

[Igor Mammedov <imammedo@redhat.com>]

On Fri, 20 May 2022 11:56:02 +0200
Li Zhang <lizhang@suse.de> wrote:

> When no memory backend is specified in machine options,
> a default memory device will be added with default_ram_id.
> However, if a memory backend object is added in QEMU options
> and id is the same as default_ram_id, a coredump happens.
> 
> Command line:
> qemu-system-x86_64 -name guest=vmtest,debug-threads=on \
> -machine pc-q35-6.0,accel=kvm,usb=off,vmport=off \
> -smp 16,sockets=16,cores=1,threads=1 \
> -m 4G \
> -object memory-backend-ram,id=pc.ram,size=4G \
> -no-user-config -nodefaults -nographic
> 
> Stack trace of thread 16903:
>     #0  0x00007fb109a9318b raise (libc.so.6 + 0x3a18b)
>     #1  0x00007fb109a94585 abort (libc.so.6 + 0x3b585)
>     #2  0x0000558c34bc89be error_handle_fatal (qemu-system-x86_64 + 0x9c89be)
>     #3  0x0000558c34bc8aee error_setv (qemu-system-x86_64 + 0x9c8aee)
>     #4  0x0000558c34bc8ccf error_setg_internal (qemu-system-x86_64 + 0x9c8ccf)
>     #5  0x0000558c349f6899 object_property_try_add (qemu-system-x86_64 + 0x7f6899)
>     #6  0x0000558c349f7df8 object_property_try_add_child (qemu-system-x86_64 + 0x7f7df8)
>     #7  0x0000558c349f7e91 object_property_add_child (qemu-system-x86_64 + 0x7f7e91)
>     #8  0x0000558c3454686d create_default_memdev (qemu-system-x86_64 + 0x34686d)
>     #9  0x0000558c34546f58 qemu_init_board (qemu-system-x86_64 + 0x346f58)
>     #10 0x0000558c345471b9 qmp_x_exit_preconfig (qemu-system-x86_64 + 0x3471b9)
>     #11 0x0000558c345497d9 qemu_init (qemu-system-x86_64 + 0x3497d9)
>     #12 0x0000558c344e54c2 main (qemu-system-x86_64 + 0x2e54c2)
>     #13 0x00007fb109a7e34d __libc_start_main (libc.so.6 + 0x2534d)
>     #14 0x0000558c344e53ba _start (qemu-system-x86_64 + 0x2e53ba)
> 
> Signed-off-by: Li Zhang <lizhang@suse.de>
> ---
>  hw/core/machine.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/hw/core/machine.c b/hw/core/machine.c
> index b03d9192ba..3867af7a8a 100644
> --- a/hw/core/machine.c
> +++ b/hw/core/machine.c
> @@ -1290,9 +1290,17 @@ MemoryRegion *machine_consume_memdev(MachineState *machine,
>  static bool create_default_memdev(MachineState *ms, const char *path, Error **errp)
>  {
>      Object *obj;
> +    ObjectProperty *prop;
>      MachineClass *mc = MACHINE_GET_CLASS(ms);
>      bool r = false;
>  
> +    prop = object_property_find(object_get_objects_root(), mc->default_ram_id);
> +    if (prop) {
> +        error_report("Memory backend id conflicts with default_ram_id %s",
> +                     mc->default_ram_id);

maybe something like this would be better:
 A memory backend with id '%s' already exists, cannot create default RAM backend with the same id.
 Either change id of the offending backend or provide system RAM backend explicitly using
 '-machine memory-backend' option.
 

> +        exit(EXIT_FAILURE);
> +    }
> +
>      obj = object_new(path ? TYPE_MEMORY_BACKEND_FILE : TYPE_MEMORY_BACKEND_RAM);
>      if (path) {
>          if (!object_property_set_str(obj, "mem-path", path, errp)) {