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Subject: Re: [PATCH v3 04/11] arm64/mm: Add set_memory_device() and
 set_memory_normal()
To: Mike Rapoport <rppt@kernel.org>
Cc: Will Deacon <will@kernel.org>, Thierry Reding
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From: Robin Murphy <robin.murphy@arm.com>
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On 07/07/2026 2:36 pm, Mike Rapoport wrote:
> On Tue, Jul 07, 2026 at 02:17:29PM +0100, Robin Murphy wrote:
>>
>> Given the precedent of memblock_mark_nomap(), as long as the reusable
>> reserved-memory regions also get split into distinct memblocks, then it
>> seems like in principle we ought to be able to give them a new
>> MEMBLOCK_PTEMAP (or whatever) flag which could then be picked up in
>> map_mem() without needing to override force_pte_mapping() globally?
> 
> Please don't. _nomap() caused enough pain.

Indeed I was there for pretty much the whole pfn_valid() saga :)

Bad example maybe - in this case the only actual similarity to nomap 
would be the fact that it would also be set by the of_reserved_mem code 
based on what it finds in DT; in all other aspects it should be 
functionally closer to something like MEMBLOCK_RSRV_NOINIT, i.e. just 
carrying information through the mm init phase, then ceasing to matter 
at all once the linear mapping is done.

Cheers,
Robin.