[libvirt] [PATCH RFC 00/39] qemu: Add support for -blockdev

[Kevin Wolf]

Am 27.07.2018 um 10:01 hat Peter Krempa geschrieben:
> On Thu, Jul 26, 2018 at 17:04:19 +0800, Fam Zheng wrote:
> > On Thu, 07/26 10:44, Kevin Wolf wrote:
> > > Am 25.07.2018 um 17:57 hat Peter Krempa geschrieben:
> > > > This series adds support for starting and hotplug of disks with
> > > > -blockdev/blockdev-add.
> > > > 
> > > > Blockjobs are not supported and thus the last patch should not be
> > > > applied yet as some refactoring of the jobs is required.
> > > > 
> > > > At the beginning of the series there are a few cleanup patches which may
> > > > be pushed even at this point.
> > > > 
> > > > The main reason this is in RFC state is that block stats reporting does
> > > > not work.
> > > > 
> > > > The following command:
> > > > 
> > > > {"execute":"query-blockstats","arguments":{"query-nodes":true}}
> > > 
> > > query-nodes was added in commit f71eaa74c0b by Fam and Max, CCed. I'm
> > > not sure what it was needed for at all and the commit message doesn't
> > > help with that, but I suppose the addition was related to
> > > wr_highest_offset (see below).
> > 
> > Yes, this was part of RHBZ 1158094. Sorry about the poor commit message.
> 
> Well the problem is that when using -blockdev with 'query-nodes' false/not present you get a
> even more useless output:
> 
> virsh qemu-monitor-command --pretty upstream '{"execute":"query-blockstats","arguments":{"query-nodes":false}}'
> {
>   "return": [
> 
>   ],
>   "id": "libvirt-20"
> }

That's a problem. Apparently it ignores anonymous BlockBackends, which
it shouldn't do. I'll look into that.

> 'query-named-block-nodes' don't provide the 'stats' section either:
> (other drives snipped)
[...]
> Thus libvirt can't provide the stats it used to with -drive. Since we
> need to special-case the code for gathering stats for -blockdev it
> should not be a problem if e.g. query-named-block-nodes reported the
> stats section along. (perhaps with a boolean flag to do so which also
> could disable the nesting)

The only one it could theoretically provide is wr_highest_offset, the
other ones simply don't exist at the node level. And this is probably
not the only one you're interested in.

> In either case we need the stats in the same extent as we had before
> with -drive and query-blockstats.

Yes, that's clear.

Kevin
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