Re: [Xen-devel] Reserved-memory node handling in XEN ( WAS Re: [ARM] Handling CMA pool device nodes in Dom0)

[Julien Grall <julien.grall@xxxxxxx>]

On 26/07/17 16:04, Andrii Anisov wrote:
> Dear All,
Hi,

> I would like to revive this thread within the R-Car Gen3 support nits
> cleanup work.
>
>
> On 01.12.16 02:12, Stefano Stabellini wrote:
> > > Before answering about possible implementation in Xen, I would like to
> > > understand what are the constraints on these reserved memory regions.
> > >
> > > I understand that when "reg" property is specified, it is a static
> > > allocation
> > > and we need to be able to map those regions at the same address in DOM0.
> Yes, this should be like that.
>
> > > However, do these regions need to be included in memory node?
> I guess this regions should be included into the memory node. But from
> this point of view, it is not clear if the size of the reserved region
> should be accounted during RAM space allocation for the domain.
If you use the memory allocator for those reserved region, then they 
should be accounted in the domain memory. If not, then they are entirely 
separated and then no need to account them. Just add a separate memory 
node for it.
> > Another question: what caching attributes do they need in the stage2
> > mapping?
> I guess Write-Back Cacheable should be sufficient.
write-back cacheable is quite weak attribute for stage-2. Is that safe?

Cheers,

--
Julien Grall

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