From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from fout-a1-smtp.messagingengine.com (fout-a1-smtp.messagingengine.com [103.168.172.144]) (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 90CDC303C91; Tue, 18 Nov 2025 14:08:31 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=103.168.172.144 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763474913; cv=none; b=Dj9Ri+lyQA2DtbGPel8qsa8n+iLyY+iyhMCCPR+9ZqfWXo3V+/cj3fb7KEzX2a3+p/NYvLKgM2o1cNyRZJ2aborzhcm+iNwog0p2xnBgxrfyfCugzFuj1DqaJK1CUW3TmjZ5DjmbE2y3TSxEZUHp+jbcLs1NtsbpDU4Zlj8FXWA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763474913; c=relaxed/simple; bh=AFhvFdKp8cfviH/VE/ujKO75Ktut5W9gP4pzr0hI7OM=; h=MIME-Version:Date:From:To:Cc:Message-Id:In-Reply-To:References: Subject:Content-Type; b=SjfcsjmIGjbKNgJ8U4mtggvfnT6p5ezPc6tgtKS7wCCh2soeW2gmfl8LPs1dPxc2BAYCyrPG8mf8XGiFqZsPYNhNCIOSA07iZUHgVzZNyq50PVhDGgSC8qu+b4wBwtsmXPtkez01GKI2bwbi8fQ8jGKnJZoQytFyMuRtbsC2RHM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arndb.de; spf=pass smtp.mailfrom=arndb.de; dkim=pass (2048-bit key) header.d=arndb.de header.i=@arndb.de header.b=bLodE3qc; dkim=pass (2048-bit key) header.d=messagingengine.com header.i=@messagingengine.com header.b=O6S6Jjfw; arc=none smtp.client-ip=103.168.172.144 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arndb.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arndb.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=arndb.de header.i=@arndb.de header.b="bLodE3qc"; dkim=pass (2048-bit key) header.d=messagingengine.com header.i=@messagingengine.com header.b="O6S6Jjfw" Received: from phl-compute-04.internal (phl-compute-04.internal [10.202.2.44]) by mailfout.phl.internal (Postfix) with ESMTP id C4216EC0387; Tue, 18 Nov 2025 09:08:30 -0500 (EST) Received: from phl-imap-02 ([10.202.2.81]) by phl-compute-04.internal (MEProxy); Tue, 18 Nov 2025 09:08:30 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=arndb.de; h=cc :cc:content-transfer-encoding:content-type:content-type:date :date:from:from:in-reply-to:in-reply-to:message-id:mime-version :references:reply-to:subject:subject:to:to; s=fm3; t=1763474910; x=1763561310; bh=mGrPjlDKcSRS8SFdifciDeDEyPLLdWcog8pI3LOst04=; b= bLodE3qcYA8cW6ETmFBpP1bjiHBvPPdw8nZHpaNtgu8rZOP5P4h+0XBZqD4IA24v 4Gk675cJ+OuJnfmKeWsuZWDZyfCOc8GmWIu16HTtbx2vhPMzSkls6NXLzNZkp05N 8NSpQrVSxlpU97MKHos2ozDsMH3knhGyN5A9tDzpAaIFL8/hf+wbvAaB9hL2vF9F 6geZj29v8actZFibYwwS/4uoJBtSUl8EJj/nqAx58jg/yml2IfkUyoEH/Gj/KQJn 4IW/lwiai4HrHAzlUGsaOb7ZTBr3Pi/Dy02E/upSmoq8ut4HDEOPa5BdJKuh3DuY On6dpDJd+SJt8AFtyThZTw== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=cc:cc:content-transfer-encoding :content-type:content-type:date:date:feedback-id:feedback-id :from:from:in-reply-to:in-reply-to:message-id:mime-version :references:reply-to:subject:subject:to:to:x-me-proxy :x-me-sender:x-me-sender:x-sasl-enc; s=fm3; t=1763474910; x= 1763561310; bh=mGrPjlDKcSRS8SFdifciDeDEyPLLdWcog8pI3LOst04=; b=O 6S6Jjfw/Sx834SqiUMlwToFMSKNX5HiVCfvCmHKC/e4KK6fWueGialkEW7yAcOGm 4OnEVr/EUnhIcYuVj/bFdYSUYff7Tf7nkD00mE+W9x15PyvvrGt/RQKYCdPBShpM jRJZm3V8q/00NRUv9DtfdpyiN63E6OChJ41p+odFC9Q6CagJ0H7TtnoIDVb7aChl pbCOGeWEnAhzbPRjqcEcE9cJ3cHMzNfCHL1uxjiv1kaKVDBtsChHlyhK8d83ywZV gdjw2h4TkQ4foB92oqb/HaS3pAXMmXV0xldliCrwjjDQ2RXmPUW38sGtMxvBlsdF MUTacIYvFj/+tYlA/Vxvw== X-ME-Sender: X-ME-Proxy-Cause: gggruggvucftvghtrhhoucdtuddrgeeffedrtdeggddvvdduhedvucetufdoteggodetrf dotffvucfrrhhofhhilhgvmecuhfgrshhtofgrihhlpdfurfetoffkrfgpnffqhgenuceu rghilhhouhhtmecufedttdenucesvcftvggtihhpihgvnhhtshculddquddttddmnecujf gurhepofggfffhvfevkfgjfhfutgfgsehtjeertdertddtnecuhfhrohhmpedftehrnhgu uceuvghrghhmrghnnhdfuceorghrnhgusegrrhhnuggsrdguvgeqnecuggftrfgrthhtvg hrnhepfeffleeludehheeljedthfehgedtffehtdffieelheekteffvedtgeehudfhiedu necuffhomhgrihhnpehkvghrnhgvlhdrohhrghdpghhithhhuhgsrdgtohhmnecuvehluh hsthgvrhfuihiivgeptdenucfrrghrrghmpehmrghilhhfrhhomheprghrnhgusegrrhhn uggsrdguvgdpnhgspghrtghpthhtohepuddtpdhmohguvgepshhmthhpohhuthdprhgtph htthhopehjihgrgihunhdrhigrnhhgsehflhihghhorghtrdgtohhmpdhrtghpthhtohep tghhvghnhhhurggtrghisehkvghrnhgvlhdrohhrghdprhgtphhtthhopehguhhorhgvnh eskhgvrhhnvghlrdhorhhgpdhrtghpthhtoheplhhoohhnghgrrhgthheslhhishhtshdr lhhinhhugidruggvvhdprhgtphhtthhopegthhgvnhhhuhgrtggriheslhhoohhnghhsoh hnrdgtnhdprhgtphhtthhopehlihiguhgvfhgvnhhgsehlohhonhhgshhonhdrtghnpdhr tghpthhtoheplhhihigrfigviheslhhoohhnghhsohhnrdgtnhdprhgtphhtthhopehlih hnuhigqdgrrhgthhesvhhgvghrrdhkvghrnhgvlhdrohhrghdprhgtphhtthhopehlihhn uhigqdhkvghrnhgvlhesvhhgvghrrdhkvghrnhgvlhdrohhrgh X-ME-Proxy: Feedback-ID: i56a14606:Fastmail Received: by mailuser.phl.internal (Postfix, from userid 501) id E20E1700063; Tue, 18 Nov 2025 09:08:29 -0500 (EST) X-Mailer: MessagingEngine.com Webmail Interface Precedence: bulk X-Mailing-List: linux-arch@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-ThreadId: Amcp8um3uPZB Date: Tue, 18 Nov 2025 15:07:59 +0100 From: "Arnd Bergmann" To: "Huacai Chen" , "Huacai Chen" Cc: loongarch@lists.linux.dev, Linux-Arch , "Xuefeng Li" , guoren , "WANG Xuerui" , "Jiaxun Yang" , linux-kernel@vger.kernel.org, "Yawei Li" Message-Id: <29e20a47-3752-49a6-8e3d-ae4ce9ffce5b@app.fastmail.com> In-Reply-To: <20251118112728.571869-1-chenhuacai@loongson.cn> References: <20251118112728.571869-1-chenhuacai@loongson.cn> Subject: Re: [PATCH V2 00/14] LoongArch: Add basic LoongArch32 support Content-Type: text/plain Content-Transfer-Encoding: 7bit On Tue, Nov 18, 2025, at 12:27, Huacai Chen wrote: > LoongArch includes a reduced 32-bit version (LA32R), a standard 32-bit > version (LA32S) and a 64-bit version (LA64). LoongArch32 use FDT as its > boot protocol which is already supported in LoongArch64. LoongArch32's > ILP32 ABI use the same calling convention as LoongArch64. > > This patchset is adding basic LoongArch32 support in mainline kernel, it > is the successor of Jiaxun Yang's previous work (V1): > https://lore.kernel.org/loongarch/20250102-la32-uapi-v1-0-db32aa769b88@flygoat.com/ > > We can see a complete snapshot here: > https://github.com/chenhuacai/linux/tree/loongarch-next I looked through all the patches, and this seems completely fine implementation-wise. I replied with a few minor comments, but found no show-stoppers. Reviewed-by: Arnd Bergmann I'm still skeptical about the usefulness overall and would warn you that you may regret merging this in a few years: 32-bit Linux is clearly in decline, and the amount of work in bringing up and maintaining another ABI (or two if you count LA32R/S separately) is substantial. In your cover letter, I'm missing information about running LA32 code on LA64 hardware. Specifically, do you plan to add CONFIG_COMPAT support later, and do you plan to support LA32 kernels running on LA64-capable hardware? I would suggest supporting COMPAT 32-bit userspace here, but not 32-bit kernels: based on the experience with x86, arm, powerpc and mips platforms that allow both, the compat mode usually results in a much better experience overall. Compat support should probably be a follow-up and not part of the initial submission though, so what you have here is fine. Arnd