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Fri, 13 Nov 2026 11:58:11 -0800 (PST) Received: from [172.22.0.2] ([50.175.87.158]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2ee0f7e5055sm14868305ad.39.2026.11.13.11.58.10 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 13 Nov 2026 11:58:11 -0800 (PST) Date: Fri, 13 Nov 2026 11:58:08 -0800 From: Chris Down To: Vineet Gupta 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 Subject: Re: [RFC PATCH 1/2] percpu: do not put btf_type_tag on per-cpu variable declarations In-Reply-To: <20261110012235.1024461-2-vineet.gupta@linux.dev> References: <20261110012235.1024461-1-vineet.gupta@linux.dev> <20261110012235.1024461-2-vineet.gupta@linux.dev> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Disposition: inline Message-ID: <20261113115808.87a52a7c74e293ce@chrisdown.name> User-Agent: Mutt/2.4.3 (cc9e3943) (2026-10-09) 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? 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. Once the commit message nits are fixed, please feel free to add: Reviewed-by: Chris Down Tested-by: Chris Down Thanks! Chris