Re: [Qemu-devel] [PATCH v2] dump-guest-memory.py: fix "You can't do that without a process to debug"

[Laszlo Ersek <lersek@redhat.com>]

On 12/12/17 18:22, Marc-André Lureau wrote:
> If the script is run with a core (no running process), it produces an
> error:
> 
> (gdb)  dump-guest-memory /tmp/vmcore X86_64
> guest RAM blocks:
> target_start     target_end       host_addr        message count
> ---------------- ---------------- ---------------- ------- -----
> 0000000000000000 00000000000a0000 00007f7935800000 added       1
> 00000000000a0000 00000000000b0000 00007f7934200000 added       2
> 00000000000c0000 00000000000ca000 00007f79358c0000 added       3
> 00000000000ca000 00000000000cd000 00007f79358ca000 joined      3
> 00000000000cd000 00000000000e8000 00007f79358cd000 joined      3
> 00000000000e8000 00000000000f0000 00007f79358e8000 joined      3
> 00000000000f0000 0000000000100000 00007f79358f0000 joined      3
> 0000000000100000 0000000080000000 00007f7935900000 joined      3
> 00000000fd000000 00000000fe000000 00007f7934200000 added       4
> 00000000fffc0000 0000000100000000 00007f7935600000 added       5
> Python Exception <class 'gdb.error'> You can't do that without a process to debug.:
> Error occurred in Python command: You can't do that without a process
> to debug.
> 
> Replace the object_resolve_path_type() function call call with a
> local volatile variable.

Patch looks great and the above is fine with me too -- I just note we
have "call call", which could be improved. But, I don't insist.

Reviewed-by: Laszlo Ersek <lersek@redhat.com>

Thanks!
Laszlo

> 
> Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
> ---
> 
> v2:
>  - use a vmcoreinfo_realize() local volatile variable
>  - tweak commit message
> 
> scripts/dump-guest-memory.py | 3 +--
>  hw/misc/vmcoreinfo.c         | 3 +++
>  2 files changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/scripts/dump-guest-memory.py b/scripts/dump-guest-memory.py
> index 1af26c1a45..09bec92b50 100644
> --- a/scripts/dump-guest-memory.py
> +++ b/scripts/dump-guest-memory.py
> @@ -546,8 +546,7 @@ shape and this command should mostly work."""
>          return None
>  
>      def add_vmcoreinfo(self):
> -        vmci = '(VMCoreInfoState *)' + \
> -               'object_resolve_path_type("", "vmcoreinfo", 0)'
> +        vmci = 'vmcoreinfo_realize::vmcoreinfo_state'
>          if not gdb.parse_and_eval("%s" % vmci) \
>             or not gdb.parse_and_eval("(%s)->has_vmcoreinfo" % vmci):
>              return
> diff --git a/hw/misc/vmcoreinfo.c b/hw/misc/vmcoreinfo.c
> index 31db57ab44..a2805527cb 100644
> --- a/hw/misc/vmcoreinfo.c
> +++ b/hw/misc/vmcoreinfo.c
> @@ -35,6 +35,8 @@ static void vmcoreinfo_realize(DeviceState *dev, Error **errp)
>  {
>      VMCoreInfoState *s = VMCOREINFO(dev);
>      FWCfgState *fw_cfg = fw_cfg_find();
> +    /* for gdb script dump-guest-memory.py */
> +    static VMCoreInfoState * volatile vmcoreinfo_state G_GNUC_UNUSED;
>  
>      /* Given that this function is executing, there is at least one VMCOREINFO
>       * device. Check if there are several.
> @@ -56,6 +58,7 @@ static void vmcoreinfo_realize(DeviceState *dev, Error **errp)
>                               &s->vmcoreinfo, sizeof(s->vmcoreinfo), false);
>  
>      qemu_register_reset(vmcoreinfo_reset, dev);
> +    vmcoreinfo_state = s;
>  }
>  
>  static const VMStateDescription vmstate_vmcoreinfo = {
>