Re: [Qemu-devel] [PATCH v4 2/2] vl: Deprecate auto-loading of qemu.conf

[Markus Armbruster]

Eduardo Habkost <address@hidden> writes:

> On Wed, Oct 04, 2017 at 09:23:08AM -0300, Eduardo Habkost wrote:
>> On Wed, Oct 04, 2017 at 07:42:17AM +0200, Markus Armbruster wrote:
>> > Eduardo Habkost <address@hidden> writes:
>> > 
>> > > In case there were options set in the default config file, print
>> > > a warning so users can update their scripts.
>> > >
>> > > If somebody wants to keep the config file as-is, avoid the
>> > > warning and use a command-line that will work in future QEMU
>> > > versions, they can use:
>> > >
>> > >  $QEMU -no-user-config -readconfig /etc/qemu/qemu.conf
>> > >
>> > > I was going to include the suggestion in the warning message, but
>> > > I thought it could make it more confusing.  The suggestion is
>> > > documented in qemu-doc.texi.
>> > >
>> > > Signed-off-by: Eduardo Habkost <address@hidden>
>> > > ---
>> > > Changes v3 -> v4:
>> > > * Use warn_report() instead of error_report("warning: ...")
>> > >   (Eric Blake)
>> > > * Document as a deprecated feature in qemu-doc.texi
>> > > * Update subject line
>> > >   (was: "vl: Print warning when a default config file is loaded")
>> > >
>> > > Changes v2 -> v3:
>> > > * Rebase (no code changes)
>> > > * Commit message update: suggest -no-user-config
>> > > ---
>> > >  vl.c          | 6 ++++++
>> > >  qemu-doc.texi | 8 ++++++++
>> > >  2 files changed, 14 insertions(+)
>> > >
>> > > diff --git a/vl.c b/vl.c
>> > > index 3fed457921..1b0ecdf74e 100644
>> > > --- a/vl.c
>> > > +++ b/vl.c
>> > > @@ -3066,6 +3066,12 @@ static int qemu_read_default_config_file(void)
>> > >          return ret;
>> > >      }
>> > >  
>> > > +    if (ret > 0) {
>> > > +        loc_set_none();
>> > 
>> > Sure we need this here?
>> 
>> IIRC we needed it in the original version, but I don't remember
>> why.  I will check this.
>
> This is the result if we don't clear error location state:
>
>   $ ./x86_64-softmmu/qemu-system-x86_64 -monitor stdio -display none -device 
> foobar
>   qemu-system-x86_64: -device foobar: warning: Future QEMU versions won't 
> load /usr/local/etc/qemu/qemu.conf automatically
>                       ^^^^^^^^^^^^^^
>
> However, it's probably better to do this right after the loop,
> just like we already do in the second option parsing loop:
>
> Signed-off-by: Eduardo Habkost <address@hidden>
> ---
> diff --git a/vl.c b/vl.c
> index f9acc17c01..a8fd247d71 100644
> --- a/vl.c
> +++ b/vl.c
> @@ -3067,7 +3067,6 @@ static int qemu_read_default_config_file(void)
>      }
>  
>      if (ret > 0) {
> -        loc_set_none();
>          warn_report("Future QEMU versions won't load %s automatically",
>                       CONFIG_QEMU_CONFDIR "/qemu.conf");
>      }
> @@ -3224,6 +3223,11 @@ int main(int argc, char **argv, char **envp)
>              }
>          }
>      }
> +    /*
> +     * Clear error location left behind by the loop.
> +     * Best done right after the loop.  Do not insert code here!
> +     */
> +    loc_set_none();
>  
>      if (userconfig) {
>          if (qemu_read_default_config_file() < 0) {

Hmm, could this hunk be a bug fix?  Consider before the patch:

    qemu_read_default_config_file()
        qemu_read_config_file()
            qemu_config_parse()
                error_report() or error_report_err()

I suspect this uses current location left behind by the loop
inappropriately.  If true, the hunk should be a separate bug fix patch.