Re: [Qemu-devel] [PATCH V4 4/4] fw_cfg: insert fw_cfg file blobs via qemu cmdline

["Michael S. Tsirkin" <mst@redhat.com>]

On Mon, Jun 01, 2015 at 01:26:53PM +0200, Laszlo Ersek wrote:
> On 06/01/15 12:48, Michael S. Tsirkin wrote:
> > On Mon, Jun 01, 2015 at 12:43:35PM +0200, Paolo Bonzini wrote:
> >>
> >>
> >> On 01/06/2015 12:23, Michael S. Tsirkin wrote:
> >>> Still, reserving part of the namespace for QEMU internal use
> >>> is *not* policy, it's just good engineering.
> >>>
> >>> How about we forbid adding files under "etc/" ?
> >>>
> >>> That would be enough to avoid conflicts.
> >>
> >> I do not understand.  What we're doing is free-beer.  We can always say
> >> no.  What's your worry?
> > 
> > Someone writes a tool using a specific path.
> > We then add same path upstream, script breaks.
> > 
> >> One usecase of this feature is to avoid recompiling QEMU while playing
> >> with firmware.  If you cannot mimic QEMU's behavior (which is to add
> >> "etc/" files), the feature is pointless, or at least I totally cannot
> >> understand its purpose and I'm against merging it.
> >>
> >> Paolo
> > 
> > Confused.  Why does it produce the warning then?
> > 
> > If it's just for playing games, add a configure
> > switch to enable it, and disable by default.
> > Don't set traps for users.
> 
> The site specific feature can be long-term for a given site. It might
> live across several QEMU upgrades. New version of QEMU introdces a new
> fw_cfg file, might conflict with user's file from earlier. Unless the
> user places it under opt/. For that reason we emit a warning, but do not
> forcefully prevent the user from shooting his foot off.
> 
> Laszlo

I'm sorry - I don't understand. It's easy to do the right thing.  Just
add the opt prefix. Why insist on user doing the right thing, and punish
violations with failing at random?

If it's useful for developers somehow, add a config flag for that.

-- 
MST