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

["Tian, Kevin" <kevin.tian@xxxxxxxxx>]

> From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
> Sent: Monday, January 12, 2015 8:03 PM
> 
> >>> On 12.01.15 at 12:41, <kevin.tian@xxxxxxxxx> wrote:
> >>  From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
> >> Sent: Monday, January 12, 2015 7:37 PM
> >>
> >> >>> On 12.01.15 at 12:22, <kevin.tian@xxxxxxxxx> wrote:
> >> >>  From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
> >> >> Sent: Monday, January 12, 2015 6:23 PM
> >> >> One of my main problems with all you recent argumentation here
> >> >> is the arbitrary use of the 1Gb boundary - there's nothing special
> >> >> in this discussion with where the boundary is. Everything revolves
> >> >> around the (undue) effect of report-all on domains not needing all
> >> >> of the ranges found on the host.
> >> >>
> >> >
> >> > I'm not sure which part of my argument is not clear here. report-all
> >> > would be a problem here only if we want to fix all the conflictions
> >> > (then pulling unnecessary devices increases the confliction possibility)
> >> > in the domain builder. but if we only fix reasonable ones (e.g. >3GB)
> >> > while warn other conflictions (e.g. <3G) in domain builder (let later
> >> > assignment path to actually fail if confliction does matter),
> >>
> >> And have no way for the user to (securely) avoid that failure. Plus
> >> the definition of "reasonable" here is of course going to be arbitrary.
> >
> > actually here I didn't get your point then. It's your proposal to make
> > reasonable assumption like below:
> >
> > ---
> > d) Move down the lowmem RAM/MMIO boundary so that a single,
> > contiguous chunk of lowmem results, with all other RAM moving up
> > beyond 4Gb. Of course RMRRs below the 1Mb boundary must not be
> > considered here, and I think we can reasonably safely assume that
> > no RMRRs will ever report ranges above 1Mb but below the host
> > lowmem RAM/MMIO boundary (i.e. we can presumably rest assured
> > that the lowmem chunk will always be reasonably big).
> 
> Correct - but my point is that this won't work well with your report-all
> mechanism, only with the report-sel one.
> 

I've explained this several times. If there's a violation on above assumption 
from required devices, same for report-all and report-sel. If the violation is 
caused by unnecessary devices, please note I'm proposing 'warn' here so
report-all at most just adds more warnings in domain builder. the conflict
will be caught later if it becomes relevant to be assigned (e.g. thru hotplug).

Thanks
Kevin

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