From patchwork Wed Nov 30 23:41:26 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Conor Dooley X-Patchwork-Id: 13060823 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 37814C47089 for ; Thu, 1 Dec 2022 00:12:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To: Message-Id:Date:Subject:Cc:To:From:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=uPlJmaS2QG2scUoJEu3IbT2iN+t6kuvwIgIFcPIXD8E=; b=wjwvJy/CvlGC9A GfKBECAQNdY3vJxMPOn7WG283RvBbK0nFqoV1mcwwiaN/eL5qmmjVUYLuHIgP6m6+fMgAso2AjDGF up1WfRkRDFUJ5Oq5xuodT26j6uX8aHxRKt/8cL3LH0flhJHntw9Tyw2P26MIHysqZw8bDv0e/RYAE cA+DxGmLwsfl7Y3WlbC/j4C8BEeEM5jPQ9OeuxEpt0Tkl01HV4n3KaizsQ1az5hdzd3ia+V7l3OvF ojsaQTEy3ote/nrgHaX+NUqOCc84SVZbZkhRAvn7mbzZbbCHUmz0QLivXwVst3XaC7HrAAazxE8l0 LA4P3drfnrROIbWakjhg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1p0XBM-003X5v-6d; Thu, 01 Dec 2022 00:12:04 +0000 Received: from ams.source.kernel.org ([2604:1380:4601:e00::1]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1p0WiN-003Jpr-OL for linux-riscv@lists.infradead.org; Wed, 30 Nov 2022 23:42:09 +0000 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 63BABB81D76; Wed, 30 Nov 2022 23:42:06 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id B89BFC4347C; Wed, 30 Nov 2022 23:42:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1669851725; bh=Z7aEnVV+jWqoN52K1e+YmgnpAmHL+qz1PmK3NhAzRxQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=EnIw4/IrxANCSz/9VMiRA2KIF6h3JhMAHa/K90/tVJu+PWuZwyGcVwk6Y/zm+B+jL SlBUCNPTLbcVhrHzZob+j5KwC/UXl07hBKXLBafS0wmQjHhK9Fw9J/vp4+JR7Y94uS TBP2keeu8Tg48fv4xCCzWzvNHS7gGuGlALoUG+FhDzeU/snOwUnk+ZLnOvmNTK/YGA lnuxunckxgcjRYxr0IB9pBW+hzIHmoPtb27IEAy2PWT44dlttLMlsVwte40Y/vhbPA sVQJHXRlDzCKMWkh3ALONUhRQT9ISq2l2EOKGhVynuXRuW2SWJGFVPd6riRsdahpDe SiRZLV22KB8Hw== From: Conor Dooley To: Palmer Dabbelt , linux-riscv@lists.infradead.org Cc: Conor Dooley , ajones@ventanamicro.com, aou@eecs.berkeley.edu, conor@kernel.org, corbet@lwn.net, guoren@kernel.org, heiko@sntech.de, paul.walmsley@sifive.com, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org Subject: [PATCH v1 3/3] Documentation: riscv: add a section about ISA string ordering in /proc/cpuinfo Date: Wed, 30 Nov 2022 23:41:26 +0000 Message-Id: <20221130234125.2722364-4-conor@kernel.org> X-Mailer: git-send-email 2.38.1 In-Reply-To: <20221130234125.2722364-1-conor@kernel.org> References: <20221130234125.2722364-1-conor@kernel.org> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20221130_154208_137999_4F32A1E0 X-CRM114-Status: GOOD ( 12.75 ) X-BeenThere: linux-riscv@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-riscv" Errors-To: linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org From: Conor Dooley The RISC-V specs are permissive in what they allow as the ISA string, but how we output this to userspace in /proc/cpuinfo is quasi uAPI. Formalise this as part of the uAPI, by documenting the list of rules we use at this point in time. Signed-off-by: Conor Dooley --- I've not "tested" these docs. The NIPA-esque pwbot should go and test it AFAICT. If it doesn't, I'll go add that. --- Documentation/riscv/uabi.rst | 42 ++++++++++++++++++++++++++++++++++++ 1 file changed, 42 insertions(+) diff --git a/Documentation/riscv/uabi.rst b/Documentation/riscv/uabi.rst index 21a82cfb6c4d..bc3c8ced644b 100644 --- a/Documentation/riscv/uabi.rst +++ b/Documentation/riscv/uabi.rst @@ -3,4 +3,46 @@ RISC-V Linux User ABI ===================== +Misaligned accesses +------------------- + Misaligned accesses are supported in userspace, but they may perform poorly. + +ISA string ordering in /proc/cpuinfo +------------------------------------ + +The canonical order of ISA extension names in the ISA string is defined in +chapter 27 of the unprivileged specification. +The specification uses vague wording, such as should, when it comes to +ordering, so for our purposes the following rules apply: + +#. Single-letter extensions come first, in "canonical order", so + "IMAFDQLCBKJTPVH". + +#. All multi-letter extensions will be separated from other multi-letter + extensions by an underscore. + +#. Additional standard extensions (starting with 'Z') will be sorted after + single-letter extensions and before any higher-privileged extensions. + +#. The first letter following the 'Z' conventionally indicates the most + closely related alphabetical extension category, IMAFDQLCBKJTPVH. + If multiple 'Z' extensions are named, they should be ordered first by + category, then alphabetically within a category. + +#. Standard supervisor-level extensions (starting with 'S') will be listed + after standard unprivileged extensions. If multiple + supervisor-level extensions are listed, they will be ordered + alphabetically. + +#. Standard machine-level extensions (starting with 'Zxm') will be listed + after any lower-privileged, standard extensions. If multiple + machine-level extensions are listed, they will be ordered + alphabetically. + +#. Non-standard extensions (starts with 'X') will be listed after all + standard extensions. + +An example string following the order is: + rv64imadc_zifoo_zigoo_zafoo_sbar_scar_zxmbaz_xqux_xrux +