Re: [Qemu-devel] [PATCH v2] vl.c: disallow command line fw cfg without opt/

[Markus Armbruster <armbru@redhat.com>]

"Michael S. Tsirkin" <mst@redhat.com> writes:

> Allowing arbitary file names on command line is setting us up for
> failure: future guests will look for a specific QEMU-specified name and
> will get confused finding a user file there.
>
> We do warn but people are conditioned to ignore warnings by now,
> so at best that will help users debug problem, not avoid it.
>
> Disable this by default, so distros don't get to deal with it,
> but leave an option for developers to configure this in,
> with scary warnings so people only do it if they know
> what they are doing.
>
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

I'm having a hard time to see the point.  There are *countless* ways
users can mess up their guests from the command line or the monitor.
Yet we get so hung up on this rather obscure one to attempt to catch
some (but far from all) misuses that may trigger it, and then, because
that interferes with debugging, add a *configure* option to suppress it
again.

Misuse of -fw_cfg isn't even a molehill, but adding a configure option
*is* making a mountain out of it.

If you know what "fw cfg" is (few users do), and know how to put the
user-specified fw cfg files feature to use (even fewer), you're damn
well expected to know to stick to /opt or else.  We already print a
reminder.  That's as far as I'd want us to go.