Re: [PATCH v3 4/4] libxl: add support for vscsi

[Olaf Hering <olaf@aepfle.de>]

On Fri, Mar 13, Ian Campbell wrote:

> > > > > On Fri, 2015-03-06 at 10:45 +0100, Olaf Hering wrote:
> > > > > > +    ("feature_host",     bool),
> > > > > What is this feature thing? What does !host imply?
> > > > This enables raw SCSI command passthrough in xenlinux. If the flag is
> > > > off then each command is checked. The check allows many commands to
> > > > passthrough, one command needs emulation and unhandled commands are
> > > > rejected. The flag is a noop in pvops because it doesnt look at such
> > > > flag. I was told its not required, dont know the details.
> > > Sounds like it at the very least needs a better name.
> > Ok, will rename it to feature_noemul or feature_xenlinux_raw_scsicmd or
> > whatever.
> Neither of those appear to be a good description of what you say quoted
> above.

Ian, after some thought its not clear to me why the name "feature_host"
should be changed. The config option is "feature-host", the backend
expects a property named "feature-host". So it seems natural to also
name the variable that way. In the end it just passes a boolean from the
config to xenstore, nothing else is done with it.

> Also, should this be a defbool or not?

This is a good idea. I remmeber xend had code to make sure that all
devices within a vhost had the same value for "feature-host". I think
the intention was that whole physical hosts are passed to a domU. A
defbool makes it easier to preserve the initial value based on the first
config item.

Olaf