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

[Laszlo Ersek <lersek@redhat.com>]

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