Re: [RFC PATCH-for-6.2 v3] qdev-monitor: Only allow full --global <driver>.<property>=<val> option

[Daniel P . Berrangé]

On Sat, Nov 20, 2021 at 07:53:20AM +0100, Markus Armbruster wrote:
> Philippe Mathieu-Daudé <philmd@redhat.com> writes:
> 
> > When not all fields of the --global option are provided,
> > QEMU might crash:
> >
> >   $ qemu-system-x86_64 -global driver=isa-fdc
> >   qemu-system-x86_64: ../../devel/qemu/qapi/string-input-visitor.c:394:
> >   string_input_visitor_new: Assertion `str' failed.
> >   Aborted (core dumped)
> >
> > Fix by only allowing --global with all 3 fields:
> >
> >   $ qemu-system-x86_64 -global driver=isa-fdc
> >   Invalid 'global' option format. It must be provided as:
> >     --global <driver>.<property>=<value>
> >
> > Reported-by: Thomas Huth <thuth@redhat.com>
> > Suggested-by: Markus Armbruster <armbru@redhat.com>
> > Resolves: https://gitlab.com/qemu-project/qemu/-/issues/604
> > Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
> > ---
> > v3: Change qemu_global_option (Markus)
> >
> > Supersedes: <20211119122911.365036-1-philmd@redhat.com>
> > ---
> >  softmmu/qdev-monitor.c | 9 +++------
> >  1 file changed, 3 insertions(+), 6 deletions(-)
> >
> > diff --git a/softmmu/qdev-monitor.c b/softmmu/qdev-monitor.c
> > index 01f3834db57..558272b147c 100644
> > --- a/softmmu/qdev-monitor.c
> > +++ b/softmmu/qdev-monitor.c
> > @@ -1029,13 +1029,10 @@ int qemu_global_option(const char *str)
> >          qemu_opt_set(opts, "value", str + offset + 1, &error_abort);
> >          return 0;
> >      }
> > +    printf("Invalid 'global' option format. It must be provided as:\n");
> > +    printf("  --global <driver>.<property>=<value>\n");
> >  
> > -    opts = qemu_opts_parse_noisily(&qemu_global_opts, str, false);
> > -    if (!opts) {
> > -        return -1;
> > -    }
> > -
> > -    return 0;
> > +    return -1;
> >  }
> >  
> >  bool qmp_command_available(const QmpCommand *cmd, Error **errp)
> 
> This drops a documented part of the external interface:
> 
>     $ qemu-system-x86_64 -help | grep -C 1 global
>                     i.e. -set drive.$id.file=/path/to/image
>     -global driver.property=value
> --> -global driver=driver,property=property,value=value
>                     set a global default for a driver property

This doc makes it look like the two syntaxes are functionally
equivalent, but it seems that's not quite the case.

libvirt uses the driver.propert=value syntax for everything
except one case

  -global driver=cfi.pflash01,property=secure,value=on

for that one if we try to use

  -global cfi.pflash01.secure=on

it complains

  qemu-system-x86_64: warning: global cfi.pflash01.secure has invalid class name

what's going on here ?

>     -boot [order=drives][,once=drives][,menu=on|off]
> 
> It goes back to commit 3751d7c43f "vl: allow full-blown QemuOpts syntax
> for -global", v2.4.0.
> 
> The appropriate fix is to check @opts for presence of all three
> parameters.
> 

Regards,
Daniel
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