Am 13.06.2018 um 18:41 hat Max Reitz geschrieben: > On 2018-06-13 18:02, Eric Blake wrote: > > On 06/13/2018 10:47 AM, Denis Plotnikov wrote: > >> The command enables/disables copy-on-read mode for VM's disk while > >> VM is running. > >> > >> This is needed when using external disk readers to shape access pattern > >> to the disk backend. > >> > >> Signed-off-by: Denis Plotnikov <dplotni...@virtuozzo.com> > >> --- > > > > Deferring thoughts on the actual design for later; > > But why? ;-) > > This patch would definitely be superseded by a block reconfiguration > command (i.e. presumably one that makes reopen accessible over QMP). > With such a command, you could insert or remove a copy-on-read filter > node at any point in time. > > Since we definitely want block graph configuration, I don't think we > want to add special commands now.
I agree, and it seems that we get more and more use cases for a block reconfiguration commands. Only yesterday we talked about the "true" blockdev way for libvirt to implement I/O throttling. The result was that without reopen, we still need to use the old QMP command to set BlockBackend-based I/O throttling instead of using a filter node. So I'm eagerly awaiting Berto's promised patches for it. Kevin
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