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

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

> From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
> Sent: Friday, January 09, 2015 5:24 PM
> 
> >>> On 09.01.15 at 03:29, <kevin.tian@xxxxxxxxx> wrote:
> >>  From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
> >> Sent: Thursday, January 08, 2015 8:59 PM
> >>
> >> >>> On 08.01.15 at 13:49, <George.Dunlap@xxxxxxxxxxxxx> wrote:
> >> > One question: where are these RMRRs typically located in memory?
> Are
> >> > they normally up in the MMIO region?  Or can they occur anywhere
> (even
> >> > in really low areas, say, under 1GiB)?
> >>
> >> They would typically sit in the MMIO hole or below 1Mb; that latter case
> >> is particularly problematic as it might conflict with what we want to put
> >> there (BIOS etc).
> >>
> >
> > and later case is not solvable, which is then related to other discussion
> > whether
> > we want to fail such case
> 
> That latter case is partially solvable: The BIOS put below 1Mb has a
> permanent and a transient part. Dealing with the transient part
> overlapping an RMRR ought to be possible (e.g. by delaying the
> actual device assignment until the point where hvmloader knows it
> is safe to do). An overlap of the permanent part with an RMRR is of
> course fatal.
> 

yes, but that type of changes are tricky, and since it's only partial so not
worthy of doing so. :-)

Thanks
Kevin

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