Re: [Xen-devel] (v2) Design proposal for RMRR fix

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Wed, 2015-01-14 at 09:43 +0000, Tian, Kevin wrote:
> > From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
> > Sent: Wednesday, January 14, 2015 5:00 PM
> > 
> > >>> On 14.01.15 at 09:06, <kevin.tian@xxxxxxxxx> wrote:
> > > Now the open is whether we want to fail domain creation for all of above
> > > conflicts. user may choose to bear with conflicts at his own disposal, or
> > > libxl doesn't want to fail conflicts as preparation for future
> > > hotplug/migration.
> > > One possible option is to add a per-region flag to specify whether 
> > > treating
> > > relevant conflict as an error, when libxl composes the list to domain
> > > builder.
> > > and this information will be saved in a user space database accessible to
> > > all components and also waterfall to Xen hypervisor when libxl requests
> > > actual device assignment.
> > 
> > That's certainly a possibility, albeit saying (in the guest config) that
> > a region to be reserved only when possible is about the same as
> > not stating that region. If at all, I'd see the rmrr-host value be a
> > tristate (don't, try, and force) to that effect.
> > 
> 
> how about something like below with bi-state?
> 
> for statically assigned device:
>       pci = [ "00:02.0, 0/1" ]
> where '0/1' represents try/force (or use 'try/force', or have a meaningful 
> attribute like rmrr_check=try/force?)

NB the pci syntax already supports key=value style options, so this
would have to use the more meaningful foo=try/force approach if you want
to go this route (and it's also clearly preferable from a UI pov
anyway).
> 
> for other usages like hotplug/migration:
>       reserved_regions = [ 'host, 0/1', 'start, end, 0/1', 'start, end, 0/1', 
> ...]
> If 'host' is specified, it implies rmrr_host, besides user can specific 
> explicit ranges according to his detail requirement.

Please avoid opaque "0" vs "1" values here too if you go this way.

Ian.


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