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

[Laszlo Ersek]

On 06/01/15 14:38, Michael S. Tsirkin wrote:
> 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?

I'm not insisting, just trying to explain / repeat the thought process
(from more than one month ago :)) that lead up to Gabriel's v4.

Thanks
Laszlo

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