Re: [Qemu-devel] Design of the blobstore

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

On Wed, Sep 14, 2011 at 05:12:48PM -0400, Stefan Berger wrote:
> On 09/14/2011 01:56 PM, Michael S. Tsirkin wrote:
> >On Wed, Sep 14, 2011 at 01:49:50PM -0400, Stefan Berger wrote:
> >>On 09/14/2011 01:40 PM, Michael S. Tsirkin wrote:
> >>>On Wed, Sep 14, 2011 at 01:05:44PM -0400, Stefan Berger wrote:
> >>>>qemu ... \
> >>>>     -blobstore name=my-blobstore,drive=tpm-bs,showsize \
> >>>>     -drive if=none,id=tpm-bs \
> >>>>     -tpmdev libtpms,blobstore=my-blobstore,id=tpm0 \
> >>>>     -device tpm-tis,tpmdev=tpm0
> >>>>
> >>>>which would result in QEMU printing to stdout:
> >>>>
> >>>>Blobstore tpm-store on drive with ID tpm-bs requires 83kb.
> >>>So you envision tools parsing this freetext then?
> >>>Seems like a step back, we are trying to move to QMP ...
> >>I extended it first for the way I typically interact with QEMU. I do
> >>not use the monitor much.
> >It will work even better if there's a tool to do the job instead of cut
> >and pasting stuff, won't it? And for that, we need monitor commands.
> >
> I am not so sure about the design of the QMP commands and how to
> break things up into individual calls. So does this sequence here
> and the 'query-blobstore' output look ok?
> 
> { "execute": "qmp_capabilities" }
> {"return": {}}
> { "execute": "query-blobstore" }
> {"return": [{"size": 84480, "id": "tpm-bs"}]}

I'll let some QMP experts to comment.

We don't strictly need the id here, right?
It is passed to the command.

BTW is it [] or {}? It's the total size, right? Should it be
{"return": {"size": 84480}}
?


> 
> Corresponding command line parameters are:
> 
>     -tpmdev libtpms,blobstore=tpm-bs,id=tpm0 \
>     -drive if=none,id=tpm-bs,file=$TPMSTATE \
> 
> Regards,
>     Stefan
> 
> 
> >>>So with above, the raw case which we don't expect to be used often
> >>>is easy to use, but qcow which we expect to be the main case
> >>>is close to imposible, involving manual cut and paste
> >>>of image size.
> >>>
> >>>Formatting images seems a rare enough occasion,
> >>>that I think only using monitor command for that
> >>>would be a better idea than a ton of new command
> >>>line options. On top of that, let's write a
> >>>script that run qemu, queries image size,
> >>>creates a qcow2 file, run qemu again to format,
> >>>all this using QMP.
> >>Creates the qcow2 using 'qemu-img' I suppose.
> >>
> >>    Stefan
> >Sure.
> >
> >>>WRT 'format and run in one go' I strongly disagree with it.
> >>>It's just too easy to shoot oneself in the foot.