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Re: [Xen-devel] XEN on R-CAR H3

Hi Oleksandr,

Hi, Julien

There is a question which worries me and likely other people as well. Which is "reserved memory area support in Xen". Some SoCs except application processors have some IPs (co-processors, dsps, codecs, whatever) which rely on a specific predefined memory regions, or even can work with these memory regions only...

This discussion came-up time to time on the ML. I would love to see patches we can discuss :)

Without this feature being supported, we won't be able to use IPs, whose firmware requires a predefined memory region to talk to an application processor, I am afraid. One option comes to mind... I presume, the use of "iomem" property in domain config could allow us to assign 1:1 mapped region to that guest domain. Would it be a correct option? What needs to be implementing it Xen, for example, to have a possibility to assign a particular reserved memory region(s) to a particular guest domain?

Well, for a first you need to deal with Xen and Dom0. For instance, Xen allocator should not be able to use that memory for a normal RAM page.

I understand.

There was some discussions on the ML a long time ago with Andrii (see [1]). Maybe he has some patches ready for it.


[1] https://lists.xenproject.org/archives/html/xen-devel/2017-07/msg02674.html

Thank you for the pointer. I will read it.


Oleksandr Tyshchenko

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