linux-kernel - Re: [RFC][PATCH v2 22/29] mm/numa: Register information into Kmemdump

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Message-ID: <7e1f4f64-dfc4-4366-8e01-0891b2d4d2b4@redhat.com>
Date: Mon, 1 Sep 2025 12:01:58 +0200
From: David Hildenbrand <david@...hat.com>
To: Eugen Hristev <eugen.hristev@...aro.org>, Michal Hocko <mhocko@...e.com>
Cc: linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
 linux-arch@...r.kernel.org, linux-mm@...ck.org, tglx@...utronix.de,
 andersson@...nel.org, pmladek@...e.com,
 linux-arm-kernel@...ts.infradead.org, linux-hardening@...r.kernel.org,
 corbet@....net, mojha@....qualcomm.com, rostedt@...dmis.org,
 jonechou@...gle.com, tudor.ambarus@...aro.org,
 Christoph Hellwig <hch@...radead.org>,
 Sergey Senozhatsky <senozhatsky@...omium.org>
Subject: Re: [RFC][PATCH v2 22/29] mm/numa: Register information into Kmemdump

>>> What do you think ?
>>
>> Looks a bit over-engineered, and will require us to import a header
>> (likely kmemdump.h) in these files, which I don't really enjoy.
>>
>> I would start simple, without any such macro-magic. It's a very simple
>> function after all, and likely you won't end up having many of these?
>>
> 
> Thanks David, I will do it as you suggested and see what comes out of it.
> 
> I have one side question you might know much better to answer:
> As we have a start and a size for each region, this start is a virtual
> address. The firmware/coprocessor that reads the memory and dumps it,
> requires physical addresses.

Right. I was asking myself the same question while reviewing: should we 
directly export physical ranges here instead of virtual ones. I guess 
virtual ones is ok.

What do you suggest to use to retrieve that
> address ? virt_to_phys might be problematic, __pa or __pa_symbol? or
> better lm_alias ?

All areas should either come from memblock or be global variables, right?

IIRC, virt_to_phys() should work for these. Did you run into any 
problems with them or why do you think virt_to_phys could be problematic?

-- 
Cheers

David / dhildenb