Re: [libvirt] New QEMU daemon for persistent reservations
On Tue, Oct 03, 2017 at 06:07:53PM +0200, Paolo Bonzini wrote:
On 03/10/2017 17:59, Michal Privoznik wrote:
> Ah, this breaks my design. I guess
>
> <disk>
> <pr>
> <source type='unix' path='/path/to/qemu-pr-helper'
mode='server'/>
> </pr>
> </disk>
>
> is pure madness, isn't it?
Yes, but OTOH if libvirtd starts the daemon, nobody cares about the
source type, so perhaps
<pr driver='helper' mode='shared'>
<source ... />
</pr>
(mandatory source) vs.
<pr driver='helper' mode='private'>
<path>/path/to/qemu-pr-helper</path>
</pr>
(optional path, default from global configuration) vs.
<pr driver='passthrough'/>
(no helper)?
I tend to think we should not expose the concept of a 'helper' at all in
the XML. The fact that QEMU has a separate binary to do this is really an
internal implementation detail due to the need for privilege separation/
elevation.
Libvirt should just do the right thing running the helper with a suitable
configuration when needed, just like we run the TAP device helper when
needed.
IOW, just be as simple as an attribute "reservations=on|off" and we'll
decide the UNIX socket path, daemon forking, etc ourselves
Regards,
Daniel
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