Re: [Xen-devel] Duplicated memory node in the Device-Tree (WAS [XEN] Re: Duplicated memory nodes cause the BUG())

[Andrii Anisov <andrii_anisov@xxxxxxxx>]

Hello Julien,


On 25.07.17 17:23, Julien Grall wrote:
> I think this is by chance rather than by design. The first question to 
> answer is why a Firmware would specify twice the same memory banks? Is 
> it valid from the specification?
Yep, that is the question.

> Regardless that, it looks like to me that the device-tree you give to 
> the board should not contain the memory nodes.
The device-tree is provided by vendor in that form, and u-boot is 
theirs. It seems to me that they do not really care since the kernel 
tolerates duplication.
> >  ps. Linux kernel does tolerate duplicated memory nodes by merging 
> > memory blocks. I.e. memblock_add_range() function is commented as 
> > following:
> > /**
> >      * memblock_add_range - add new memblock region
> >      * @type: memblock type to add new region into
> >      * @base: base address of the new region
> >      * @size: size of the new region
> >      * @nid: nid of the new region
> >      * @flags: flags of the new region
> >      *
> >      * Add new memblock region [@base,@base+@size) into @type. The new
> > region
> >      * is allowed to overlap with existing ones - overlaps don't affect
> > already
> >      * existing regions.  @type is guaranteed to be minimal (all
> > neighbouring
> >      * compatible regions are merged) after the addition.
> >      *
> >      * RETURNS:
> >      * 0 on success, -errno on failure.
> >      */
IMO the function description is pretty straight-forward.
But let us wait for device tree guys feedback.

--

*Andrii Anisov*



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