Re: [Xen-devel] [PATCH 2/2] expert_mode: Add a new configuration option for expert users.

[George Dunlap <george.dunlap@xxxxxxxxxxxxx>]

On 17/07/13 11:56, Ian Jackson wrote:
> Ian Campbell writes ("Re: [Xen-devel] [PATCH 2/2] expert_mode: Add a new 
> configuration option for expert users."):
> > On Fri, 2013-07-12 at 14:08 -0400, Konrad Rzeszutek Wilk wrote:
> > > This could also be called 'seatbelt' option.
> > >
> > > libxl has a variety of checks where it will fail out an operation
> > > unless the user has provided an --force (or --ignore) parameter.
> > > Currently one such check is for the 'vcpu-set' command which
> > > will error out if the count of virtual cpus is greater than the
> > > physical cpus. This parameter will ignore such checks and allow
> > > the user to do the operations without the need for override flags.
> > Does this overlap  somewhat with various commands which individually
> > take a -f(orce) option?
> Clearly it should disable all of those -f's too.
>
> > > +=item B<expert_mode=BOOLEAN>
> > > +
> > > +Do not act on host performed checks that might lead to performance
> > > +degradations. Currently checks are made for following operations:
> > > + - C<vcpu-set> - if the number of VCPUs set for a guest is higher than the
> > > +   physical count the operation will error out.
> I don't think this is a very coherent specification.  Surely it should
> override "all -f options" or something similar.
I think that makes sense for some but not all.  For example, for "xl 
shutdown", -f means "send an ACPI event if no PV drivers are detected".  
I don't think we'd want to change that behavior with such a switch.  
(Arguably -f was the wrong option to use for that in the first place, 
but it's a bit late for that now.)
 -George.

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