Re: [Qemu-devel] [V5 Patch 3/4]Qemu: Command "block_set" for dynamic block params change

[Supriya Kannery]

On 08/01/2011 09:14 PM, Anthony Liguori wrote:
> On 08/01/2011 10:44 AM, Kevin Wolf wrote:
> > Am 01.08.2011 17:28, schrieb Anthony Liguori:
> > > > 2. Top-level command for each parameter (e.g. block_set_hostcache).
> > > > Supported parameters are easily discoverable via query-commands. If
> > > > individual block devices support different sets of parameters then
> > > > they may have to return -ENOTSUPP.
> > > >
> > > > I like the block_set approach.
> > > >
> > > > Anthony, Kevin, Supriya: Any thoughts?
> > >
> > > For the sake of overall QMP sanity, I think block_set_hostcache is
> > > really our only option.
> >
> > Ideally we should have blockdev_add, and blockdev_set would just take
> > the same arguments and update the given driver.
>
> Ideally we'd have a backend_add, backend_set, etc.
>
> But in the absence of that, we should provide the best interface we can
> with the current tools we have.
>
> For now, using high level commands is the best we can do.

Will be modifying code to have 'block_set_hostcache' command 
implemented. Along with that, planning to implement 
'query-block_set_hostcache', that returns current hostcache setting
for all the applicable block devices.

I am not able to find how "query-commands" is helping out
to programmatically find out all the supported parameters
of a specific command. When I tried out, "query-commands"
is listing all the supported command names. "query-xx" is
returning current settings related to command 'xx',
but not any information related to supported parameters
of 'xx'.
Am I missing something?

> Regards,
>
> Anthony Liguori
>
> > But we don't have blockdev_add today, so whatever works for your as a
> > temporary solution...
> >
> > Kevin