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[2003:d8:2f27:6d00:7b96:afc9:83d0:5bd]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3ee073f3d68sm446010f8f.10.2025.09.17.12.03.55 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 17 Sep 2025 12:03:56 -0700 (PDT) Message-ID: Date: Wed, 17 Sep 2025 21:03:55 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC][PATCH v3 09/16] genirq/irqdesc: Have nr_irqs as non-static To: Thomas Gleixner , Eugen Hristev , 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> <7f4aa4c6-7b77-422b-9f7a-d01530c54bff@redhat.com> <87segk9az5.ffs@tglx> From: David Hildenbrand Autocrypt: addr=david@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250917_120404_257632_E4F95F50 X-CRM114-Status: GOOD ( 44.45 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org > >>> this would go to a separate section called .tagged_memory. > > That'd be confusing vs. actual memory tags, no? Yeah, I came to the conclusion just after an upstream call we just had about that topic (bi-weekly MM alignment session). I'm open for any suggestions that make it more generic. My first instinct was "named memory regions". > >> Maybe just "tagged_memory.h" or sth. like that? I'm bad at naming, so I >> would let others make better suggestions. > > inspect.h :) > > I'm going to use 'inspect' as prefix for the thoughts below, but that's > obviously subject to s/inspect/$BETTERNAME/g :) > >>> Then anyone can walk through the section and collect the data. >>> >>> I am just coming up with ideas here. >>> Could it be even part of mm.h instead of having a new header perhaps ? >>> Then we won't need to include one more. >> >> I don't really have something against a new include, just not one that >> sounded like a very specific subsystem, not something more generic. > > Right. We really don't want to have five different mechanisms for five > infrastructures which all allow to inspect kernel memory (life or > dead) in one way or the other. The difference between them is mostly: > > - Which subset of the information they expose for inspection > > - The actual exposure mechanism: crash dump, firmware storage, > run-time snapshots in a filesystem, .... > > Having one shared core infrastructure to expose data to those mechanisms > makes everyones life simpler. > > That obviously needs to collect the superset of data, but that's just a > bit more memory consumed. That's arguably significantly smaller than > supporting a zoo of mechanisms to register data for different > infrastructures. > > I'm quite sure that at least a substantial amount of the required > information can be collected at compile time in special section > tables. The rest can be collected in runtime tables, which have the same > format as the compile time section tables to avoid separate parsers. > > Let me just float some ideas here, how that might look like. It might be > completely inpractical, but then it might be at least fodder for > thoughts. Thanks a bunch for writing all that down! > > As this is specific for the compiled kernel version you can define an > extensible struct format for the table. > > struct inspect_entry { > unsigned long properties; > unsigned int type; > unsigned int id; > const char name[$MAX_NAME_LEN]; > unsigned long address; > unsigned long length; > .... > }; > > @type > refers either to a table with type information, which describes > the struct in some way or just generate a detached compile time > description. > > @id > a unique id created at compile time or via registration at > runtime. Might not be required We discussed that maybe one would want some kind of a "class" description. For example we might have to register one pgdat area per node. Giving each one a unique name might be impractical / unreasonable. Still, someone would want to select / filter out all entries of the same "class". Just a thought. > > @name: > Name of the memory region. That might go into a separate table > which is referenced by @id, but that's up for debate. Jup. > > @address: > @length: > obvious :) > > ... > Whatever a particular consumer might require > > @properties: > > A "bitfield", which allows to mark this entry as (in)valid for a > particular consumer. > > That obviously requires to modify these properties when the > requirements of a consumer change, new consumers arrive or new > producers are added, but I think it's easier to do that at the > producer side than maintaining filters on all consumer ends > forever. Question would be if that is not up to a consumer to decide ("allowlist" / filter) by class or id, stored elsewhere. > > Though I might be wrong as usual. IOW this needs some thoughts. :) > > The interesting engineering challenge with such a scheme is to come up > with a annotation mechanism which is extensible. > > Runtime is trivial as it just needs to fill in the new field in the > datastructure and all other runtime users have that zero > initialized automatically, if you get the mechanism correct in the > first place. Think in templates :) > > Compile time is a bit more effort, but that should be solvable with > key/value pairs. > > Don't even waste a thought about creating the final tables and > sections in macro magic. All the annotation macros have to do is to > emit the pairs in a structured way into discardable sections. > > Those section are then converted in post processing into the actual > section table formats and added to the kernel image. Not a > spectacular new concept. The kernel build does this already today. > > Just keep the compile time annotation macro magic simple and > stupid. It can waste 10k per entry at compile time and then let > postprocessing worry about downsizing and consolidation. Nothing to > see here :) Sounds interesting! -- Cheers David / dhildenb