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Re: [Xen-devel] [PATCH v3] docs: add PVH specification

On Tue, 23 Sep 2014 14:16:46 +0100
"Jan Beulich" <JBeulich@xxxxxxxx> wrote:

> >>> On 23.09.14 at 02:38, <mukesh.rathor@xxxxxxxxxx> wrote:
> > On Thu, 18 Sep 2014 19:19:24 +0200
> > Roger Pau Monne <roger.pau@xxxxxxxxxx> wrote:
> > 
> >> Introduce a document that describes the interfaces used on PVH.
> >> This document has been designed from a guest OS point of view
> >> (i.e.: what a guest needs to do in order to support PVH).
> > ..... 
> >> +
> >> +*TODO*: we need to figure out what to do with MMIO regions, right
> >> now Xen +sets all the holes in the native e820 to MMIO regions for
> >> Dom0 up to 4GB. We +need to decide what to do with MMIO regions
> >> above 4GB on Dom0, and what to do +for PVH DomUs with
> >> pci-passthrough.
> > 
> > My previous comment in earlier version on this:
> > 
> > "We map all non-ram regions for dom0 1:1 till the highest non-ram
> > e820 entry. If there is anything that is beyond the last e820 entry,
> > it will remain unmapped."
> But that's something that needs fixing rather than spelling out in
> the documentation. I.e. Roger having this as a TODO seems quite
> right to me.

Yes, but what Roger is saying implies we don't map above 4GB which
is incorrect. Perhaps:

We map all non-ram regions for dom0 1:1 till the last e820 entry. If the 
last entry ends below 4GB, then the remaining space is mapped 1:1 upto 4GB.
This implies that if there is any region beyond the last e820 entry above
4GB, it is not mapped.  
TODO: Map region beyond last e820 if it's above 4GB. Add support for domUs
with pci passthru.


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