Re: [RFC PATCH v2 3/3] tools, libxl: handle the iomem parameter with the memory_mapping hcall

[Julien Grall <julien.grall@linaro.org>]

Hi Ian,

On 03/14/2014 09:46 AM, Ian Campbell wrote:
>> In Arianna's case, it think it would be more than fine to implement it
>> that way, and call it from within the OS, isn't this the case, Arianna?
> 
> It's certainly an option, and it would make a lot of the toolstack side
> issues moot but I'm not at all sure it is the right answer. In
> particular although it might be easy to bodge a mapping into many OSes I
> can imagine getting such a think into something generic like Linux might
> be more tricky -- in which case perhaps the toolstack should be taking
> care of it, and that does have a certain appeal from the simplicity of
> the guest interface side of things.

The generic way for Linux (and other oses) is to use device tree
passthrough.
I still think the "iomem" is a hackish way to passthrough the hardware
to guest. People who will use this solution are aware of there kernel
should map itself the region.

>> Also, just trying to recap, for Arianna's sake, moving the
>> implementation of the DOMCTL in common code (and implementing the
>> missing bits to make it works properly, of course) is still something we
>> want, right?
> 
> *If* we go the route of having the kernel make the mapping then there is
> no need, is there?

How the kernel will map the region?

Regards,

-- 
Julien Grall