From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 486011FCFDA; Tue, 4 Mar 2025 09:42:50 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.50.34 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741081373; cv=none; b=CEX0z2xoDl2Yxq6EnJgWdEJanYF0noaiarHx7CUDhQg6WMVUAywLN9dHevVscYPzsGsJQxdBPCB4mzcmBCHCUp0wCOtvM73rhLk8Y//NHWADrEyXHJ/IKuJITAQ9XugzzJ6vzseGKJmOwANZwUAsxbrRF4YN3ZFT9KxMxm0trqQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741081373; c=relaxed/simple; bh=XwmCxjrXcMahsJEKEkslTcjHfUp6QZXWnoexz7Mrfjs=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=FDfqLcRouFy9MPPQA5EvRbrh9AhyOjuHj3JQ97JuAMuYqw2rnDQoWWJaySugKAX29mu2+HHNysbqaihRqQTshwfcS06jyuZx8dMSfQYLoGuwloCVgoDJ18kMnbJsQ7syPmD+0Ln8YlGjuspwCQyhiSB/DH/g0YM4YHMRiTecsxc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=sAD73dR4; arc=none smtp.client-ip=90.155.50.34 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="sAD73dR4" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=JV3pZtApgs6TqusViUPy5JRin7FrjXxYFUIaUJ+B9XQ=; b=sAD73dR4uuNhAcshhcuRcesBx+ eJ/C3bmv3pIIe/mG1mLKwsxL767vF9XoYK+XuLoxcB4ZcWd01zg+ESguKuTlE8fSe3DBCudwCK4QH tUYunxwMMarMT59PtDZe7o+MBlfFzUHHgWTAWR/HFTAFBcE2XGKUZOY9ifY73IjijaOidM6spsxSE TFf3w0Ou4GRQUfvuK5g12RRqcEKAkz1yfN6u5AVhvvF8TmSgpmxj7ZOfmMqoCfnW2dmEM2XmvjPlQ vWR3ZzKEgCa2Xwz1NeUER743p8ylHJVVYcWFyw0T6x121cHcZEOlLl6WIzyfEXcfnVEJRzfC1fAmf rCLuWuRQ==; Received: from 77-249-17-252.cable.dynamic.v4.ziggo.nl ([77.249.17.252] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.98 #2 (Red Hat Linux)) id 1tpOn8-00000000YOw-0yQv; Tue, 04 Mar 2025 09:42:22 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id 5C1F230049D; Tue, 4 Mar 2025 10:42:20 +0100 (CET) Date: Tue, 4 Mar 2025 10:42:20 +0100 From: Peter Zijlstra To: Menglong Dong Cc: rostedt@goodmis.org, mark.rutland@arm.com, alexei.starovoitov@gmail.com, catalin.marinas@arm.com, will@kernel.org, mhiramat@kernel.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, martin.lau@linux.dev, eddyz87@gmail.com, yonghong.song@linux.dev, john.fastabend@gmail.com, kpsingh@kernel.org, sdf@fomichev.me, jolsa@kernel.org, davem@davemloft.net, dsahern@kernel.org, mathieu.desnoyers@efficios.com, nathan@kernel.org, nick.desaulniers+lkml@gmail.com, morbo@google.com, samitolvanen@google.com, kees@kernel.org, dongml2@chinatelecom.cn, akpm@linux-foundation.org, riel@surriel.com, rppt@kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, bpf@vger.kernel.org, netdev@vger.kernel.org, llvm@lists.linux.dev Subject: Re: [PATCH v4 1/4] x86/ibt: factor out cfi and fineibt offset Message-ID: <20250304094220.GC11590@noisy.programming.kicks-ass.net> References: <20250303132837.498938-1-dongml2@chinatelecom.cn> <20250303132837.498938-2-dongml2@chinatelecom.cn> <20250303165454.GB11590@noisy.programming.kicks-ass.net> <20250304053853.GA7099@noisy.programming.kicks-ass.net> <20250304061635.GA29480@noisy.programming.kicks-ass.net> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Tue, Mar 04, 2025 at 03:47:45PM +0800, Menglong Dong wrote: > We don't have to select FUNCTION_ALIGNMENT_32B, so the > worst case is to increase ~2.2%. > > What do you think? Well, since I don't understand what you need this for at all, I'm firmly on the side of not doing this. What actual problem is being solved with this meta data nonsense? Why is it worth blowing up our I$ footprint over. Also note, that if you're going to be explaining this, start from scratch, as I have absolutely 0 clues about BPF and such.