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

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
     * is allowed to overlap with existing ones - overlaps don't affect
     * existing regions.  @type is guaranteed to be minimal (all
     * 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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