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[2003:d8:2f27:6d00:7b96:afc9:83d0:5bd]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-45f3211e8c7sm40537455e9.3.2025.09.17.08.18.51 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 17 Sep 2025 08:18:52 -0700 (PDT) Message-ID: <7f4aa4c6-7b77-422b-9f7a-d01530c54bff@redhat.com> Date: Wed, 17 Sep 2025 17:18:50 +0200 Precedence: bulk X-Mailing-List: devicetree@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC][PATCH v3 09/16] genirq/irqdesc: Have nr_irqs as non-static To: Eugen Hristev , Thomas Gleixner , linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, andersson@kernel.org, pmladek@suse.com, rdunlap@infradead.org, corbet@lwn.net, mhocko@suse.com Cc: tudor.ambarus@linaro.org, mukesh.ojha@oss.qualcomm.com, linux-arm-kernel@lists.infradead.org, linux-hardening@vger.kernel.org, jonechou@google.com, rostedt@goodmis.org, linux-doc@vger.kernel.org, devicetree@vger.kernel.org References: <20250912150855.2901211-1-eugen.hristev@linaro.org> <20250912150855.2901211-10-eugen.hristev@linaro.org> <87cy7q9k8y.ffs@tglx> <87a52u9jyl.ffs@tglx> <8df2cf28-c15e-4692-a127-6a5c966a965e@linaro.org> <2bd45749-e483-45ea-9c55-74c5ba15b012@redhat.com> <87v7lh891c.ffs@tglx> <95ff36c2-284a-46ba-984b-a3286402ebf8@redhat.com> <24d6a51d-f5f8-44d7-94cb-58b71ebf473a@linaro.org> From: David Hildenbrand Content-Language: en-US Autocrypt: addr=david@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 17.09.25 17:02, Eugen Hristev wrote: > > > On 9/17/25 17:46, David Hildenbrand wrote: >> On 17.09.25 16:10, Thomas Gleixner wrote: >>> On Wed, Sep 17 2025 at 09:16, David Hildenbrand wrote: >>>> On 17.09.25 07:43, Eugen Hristev wrote: >>>>> On 9/17/25 00:16, Thomas Gleixner wrote: >>>>>> I pointed you to a solution for that and just because David does not >>>>>> like it means that it's acceptable to fiddle in subsystems and expose >>>>>> their carefully localized variables. >>>> >>>> It would have been great if we could have had that discussion in the >>>> previous thread. >>> >>> Sorry. I was busy with other stuff and did not pay attention to that >>> discussion. >> >> I understand, I'm busy with too much stuff such that sometimes it might >> be good to interrupt me earlier: "David, nooo, you're all wrong" >> >>> >>>> Some other subsystem wants to have access to this information. I agree >>>> that exposing these variables as r/w globally is not ideal. >>> >>> It's a nono in this case. We had bugs (long ago) where people fiddled >>> with this stuff (I assume accidentally for my mental sanity sake) and >>> caused really nasty to debug issues. C is a horrible language to >>> encapsulate stuff properly as we all know. >> >> Yeah, there is this ACCESS_PRIVATE stuff but it only works with structs >> and relies on sparse IIRC. >> >>> >>>> I raised the alternative of exposing areas or other information through >>>> simple helper functions that kmemdump can just use to compose whatever >>>> it needs to compose. >>>> >>>> Do we really need that .section thingy? >>> >>> The section thing is simple and straight forward as it just puts the >>> annotated stuff into the section along with size and id and I definitely >>> find that more palatable, than sprinkling random functions all over the >>> place to register stuff. >>> >>> Sure, you can achieve the same thing with an accessor function. In case >>> of nr_irqs there is already one: irq_get_nr_irqs(), but for places which >> >> Right, the challenge really is that we want the memory range covered by >> that address, otherwise it would be easy. >> >>> do not expose the information already for real functional reasons adding >>> such helpers just for this coredump muck is really worse than having a >>> clearly descriptive and obvious annotation which results in the section >>> build. >> >> Yeah, I'm mostly unhappy about the "#include " stuff. >> >> Guess it would all feel less "kmemdump" specific if we would just have a >> generic way to tag/describe certain physical memory areas and kmemdump >> would simply make use of that. > > The idea was to make "kmemdump" exactly this generic way to tag/describe > the memory. That's probably where I got lost, after reading the cover letter assuming that this is primarily to program kmemdump backends, which I understood to just special hw/firmware areas, whereby kinfo acts as a filter. > If we would call it differently , simply dump , would it be better ? > e.g. include linux/dump.h > and then DUMP(var, size) ? > > could we call it maybe MARK ? or TAG ? > TAG_MEM(area, size) I'm wondering whether there could be any other user for this kind of information. Like R/O access in a debug kernel to these areas, exporting the ranges/names + easy read access to content through debugfs or something. Guess that partially falls under the "dump" category. Including that information in a vmcore info would probably allow to quickly extract some information even without the debug symbols around (I run into that every now and then). > > this would go to a separate section called .tagged_memory. > Maybe just "tagged_memory.h" or sth. like that? I'm bad at naming, so I would let others make better suggestions. > Then anyone can walk through the section and collect the data. > > I am just coming up with ideas here. > Could it be even part of mm.h instead of having a new header perhaps ? > Then we won't need to include one more. I don't really have something against a new include, just not one that sounded like a very specific subsystem, not something more generic. -- Cheers David / dhildenb