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

On 27/07/17 10:24, Andrii Anisov wrote:
Hello Julien,


On 26.07.17 20:06, Julien Grall wrote:
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.
I've got your point.

write-back cacheable is quite weak attribute for stage-2. Is that safe?
I guess the domain should drive the resultant cacheability because it
knows how that memory region will be used. So the weakest write-back
cacheability is the right choice. Is my understanding correct?

It really depends on the security impact here. If the reserved memory is shared with other device, what would be the impact of a domain using the wrong memory attribute?

Furthermore, using the weakest one would imply cache maintenance when the region is assigned/deassigned to/from a domain to prevent leaking data.


Julien Grall

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