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Fri, 13 Nov 2026 22:36:10 +0000 X-Mizu-Trace-ID: 752cf6fae846f8b5 X-Migadu-Flow: FLOW_OUT Message-ID: <55b6a4f6-46bf-4edd-9da3-e9cfd48e8a5c@linux.dev> Date: Fri, 13 Nov 2026 14:36:03 -0800 X-Archived-By: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH 1/2] percpu: do not put btf_type_tag on per-cpu variable declarations To: Chris Down Cc: dennis@kernel.org, tj@kernel.org, cl@gentwo.org, peterz@infradead.org, mingo@redhat.com, will@kernel.org, boqun@kernel.org, longman@redhat.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, bpf@vger.kernel.org, ast@kernel.org, andrii@kernel.org, daniel@iogearbox.net, acme@kernel.org, yonghong.song@linux.dev, eddyz87@gmail.com, martin.lau@linux.dev, nathan@kernel.org, ndesaulniers@google.com, morbo@google.com, justinstitt@google.com, llvm@lists.linux.dev References: <20261110012235.1024461-1-vineet.gupta@linux.dev> <20261110012235.1024461-2-vineet.gupta@linux.dev> <20261113115808.87a52a7c74e293ce@chrisdown.name> From: Vineet Gupta Content-Language: en-US In-Reply-To: <20261113115808.87a52a7c74e293ce@chrisdown.name> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Stat-Signature: jxq9jc4r97jzpgeoyosuxjadom6wws6a X-Rspamd-Queue-Id: 84DE6A000B X-Rspam-User: X-Rspamd-Server: rspam08 X-Spam-Status: No, score=-12.3 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,MAILING_LIST_MULTI,SPF_HELO_PASS,SPF_PASS, USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=4.0.1 X-HE-Tag: 1794609373-351490 X-HE-Meta: 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 qWhedyRe KKhtpMtPnnOksE8rRhn/N2ja0sX2n4UKYF4MGtvgsvZCVAqE+JgfvTk0CQN8disKHno7+ldNcjcRllyTWa3ccM+IlPx1cad4jhtdvlYEibR36ptmzcGuwXn5m7eFAlwNtxj7JorWTbVidqJlDztghxcl7UnPja/LH51o/GoX4HH63j/BxzAi5N9qs74L5rK+8g8ZzJXfyy4BoHwx1xCSgGOVopPGF+HJO26LZjceRPjjOkEh0b7Z7YBnNMCMOUVEza/MikoxY7JMsF1YG0KOmyljKHlOQHTeCfcSJFHEWkmi9hN8VrFEqF9PmlWikhiKItEIg Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 On 11/13/26 11:58 AM, Chris Down wrote: > Hi Vineet, > > Vineet Gupta writes: >> The message is confusing: this is a declaration, not a definition. But >> the compiler is right to object to a type tag on the aggregate, and the >> issue is fundamental: every variant of an aggregate shares one DIE, so >> there is nowhere to put it. clang drops it silently and GCC warns. > Not a big deal, but the definition in GCC's message is the definition of > struct cpuinfo_x86, not of cpu_info. It's saying the attribute is being > applied to the struct type after the struct was already defined, which is > accurate. So maybe just drop that first sentence? Oops, thanks for catching that. I misread which definition it meant. Dropping the first sentence in v2. > I've tested this with clang 23 and GCC 16. With clang, the same 280 types > and 3360 bytes of BTF go away. Likewise, with GCC, the per-cpu > declarations no longer warn, and the non-enclosed address space errors > are gone. Thanks for verifying, with both the compilers. > Once the commit message nits are fixed, please feel free to add: > > Reviewed-by: Chris Down > Tested-by: Chris Down Awesome, I'll add these in v2 Thx, -Vineet