[Qemu-devel] Re: RFC v2: blockdev_add & friends, brief rationale, QMP docs

[Avi Kivity]

On 06/10/2010 08:45 PM, Markus Armbruster wrote:
>     * Our config file format is in INI syntax.  QemuOpts correspond to
>       INI sections.  Sections can't be nested, so recursive QemuOpts
>       don't translate.
>    

git (and probably others) use

[a "b"]
    c = d

for

   a.b.c=d

>     Examples:
>
>     * Single protocol:
>
>       -blockdev id=blk1,format=raw,protocol=[file,file=fedora.img]
>
>       Requires suitable syntactic sugar to get the simple form (*).
>
>     * blkdebug
>
>       -blockdev id=blk2,format=qcow2,\
>       protocol=[blkdebug,config=test.blkdebug,\
>       protocol=[file,file=test.qcow2]]
>
>     * Avi's mirror:
>
>       -blockdev id=blk3,format=raw,\
>       protocol=[mirror,\
>       [file,file=local.img],\
>       [nbd,domain=unix,sockert=nbd-sock]]
>
> 2. We already have a syntax to specify trees, namely JSON, so use it
>
>     If -blockdev's argument starts with '{', it's a JSON object suitable
>     as argument of blockdev_add in QMP.
>
>     We still provide ordinary QemuOpts syntax for the cases that can be
>     expressed with it, i.e. single protocol.
>
>     I figure we'd want syntactic sugar for blkdebug, to permit its use
>     from the command line without having to resort to JSON.
>    

Might be nice as a general extension to QemuOpts.

> 3. Stack protocols through named references
>
>     The first protocol is "inlined" into -blockdev.  Any further
>     protocols need to be referenced by name.
>
>     Best explained by example:
>
>     * Single protocol:
>
>       -blockdev id=blk1,format=raw,protocol=file,file=fedora.img
>
>       To get the simple form (*), make protocol optional with a suitable
>       default.
>
>     * blkdebug
>
>       -blockdev id=blk2,format=qcow2,protocol=blkdebug,config=test.blkdebug,\
>       base=blk2-base
>       -blockproto id=blk2-base,protocol=file,file=test.qcow2
>
>     * Avi's mirror:
>
>       -blockdev id=blk3,format=raw,protocol=mirror,\
>       base=blk3-base1,base=blk3=base2
>       -blockproto id=blk3-base1,protocol=file,file=local.img
>       -blockproto id=blk3-base2,protocol=nbd,domain=unix,sockert=nbd-sock
>
>     Anything but a single protocol becomes pretty verbose.  Syntactic
>     sugar for the blkdebug case would be possible; not sure it's worth
>     it.
>
>     No QemuOpts syntax changes.  INI can handle this just fine.
>
>    

Looks like the least painful option as no new infrastructure is needed.  
I'd go with this.



--
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