From mboxrd@z Thu Jan 1 00:00:00 1970 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 lists.gnu.org (lists.gnu.org [209.51.188.17]) (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 9FDD0C64EC7 for ; Tue, 28 Feb 2023 17:57:24 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1pX4DV-0005SK-6T; Tue, 28 Feb 2023 12:56:45 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1pX4DO-0005Qk-PE for qemu-devel@nongnu.org; Tue, 28 Feb 2023 12:56:38 -0500 Received: from mail-wm1-x32b.google.com ([2a00:1450:4864:20::32b]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1pX4DM-0004k2-H6 for qemu-devel@nongnu.org; Tue, 28 Feb 2023 12:56:38 -0500 Received: by mail-wm1-x32b.google.com with SMTP id k37so7046006wms.0 for ; Tue, 28 Feb 2023 09:56:36 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=content-transfer-encoding:mime-version:message-id:in-reply-to:date :subject:cc:to:from:user-agent:references:from:to:cc:subject:date :message-id:reply-to; bh=Skk49i/shedgc81y2UM/JeyxDXNyTjq+cP9YqmQExiU=; b=z1EMO5YJpaz+ATxWetuC9e2BC06HKrnjBFRT/W2N9ZJypRNIQZf/yWByQ6xQd/hALe XcH65oLYDaBNq47x88aY9wWZOY9MmI3MuzaTt6KDJ2hkPhlEuZn6PxkHyIynEGs0dymV pGdAh9rQwRvwlYQRAoyphojrwnNXrlfa79SY7cH71fuHUFrwXugkjya3A3pZJjWe27LW am3DoCWSet33YemU6ij2W4vlanSfu25JCtpLeUrUEmW3FFio3ErTW58azLU8hwFA66o6 +u/SKgWoh5cvFsUA/Y154TJyhvx/s8bJRp8cm9eFuJ8akLBZmMtVUykoxTwJNm4EqutA 0uzQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:mime-version:message-id:in-reply-to:date :subject:cc:to:from:user-agent:references:x-gm-message-state:from:to :cc:subject:date:message-id:reply-to; bh=Skk49i/shedgc81y2UM/JeyxDXNyTjq+cP9YqmQExiU=; b=iT0zL8gtoeHHeSJFHcabP8yrqB2yF5aWBLr8Mr2Uo9X7XiNPlzkc5k5WVq+s9vWMCP J3c2QYJDt5DRedwO/VaIybNCP81JcWoNir8PwFnZPD52WDXkcDZN5+kzQJk44Gllj/KW Cim6WKRbmW6T1C03FpeBeMFoZez3Ht3rAKOYNjztP/VcjMdYWxjVs2FLPKLX5wEjYFwv i2rH6u5DlCHwA4A7R7FTmnhj458iqo9uRXoJFa8hqNd5HIKOaCVtzlgv1BSuYHwHX6XK rux92DgR2zRUIuvmf5YlTE36YpWkm3SpkSdBxYQfk8a2oeAicWB4r7cMig9CxmmOKJb6 HKxA== X-Gm-Message-State: AO0yUKXBZ1C25+oQmOrwwNYCS+WD5+WWSR7DyZKRNeCpx3JXGVqqyckW h5hNcciEtaqXEVzSuH6Nx9eo7w== X-Google-Smtp-Source: AK7set/Day3TBlpgqBslBbiThPWhmDDbVzmNMzNOAr1tvXfuPAnrGrbevgqstBebIr26pfrV9tupgA== X-Received: by 2002:a05:600c:4b1e:b0:3e7:cee4:f8a with SMTP id i30-20020a05600c4b1e00b003e7cee40f8amr2937351wmp.29.1677606994592; Tue, 28 Feb 2023 09:56:34 -0800 (PST) Received: from zen.linaroharston ([85.9.250.243]) by smtp.gmail.com with ESMTPSA id m4-20020a05600c4f4400b003e209b45f6bsm18041074wmq.29.2023.02.28.09.56.34 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 28 Feb 2023 09:56:34 -0800 (PST) Received: from zen (localhost [127.0.0.1]) by zen.linaroharston (Postfix) with ESMTP id CBE471FFB7; Tue, 28 Feb 2023 17:56:33 +0000 (GMT) References: <20230216025739.1211680-1-richard.henderson@linaro.org> <20230216025739.1211680-3-richard.henderson@linaro.org> User-agent: mu4e 1.9.21; emacs 29.0.60 From: Alex =?utf-8?Q?Benn=C3=A9e?= To: Richard Henderson Cc: qemu-devel@nongnu.org Subject: Re: [PATCH v2 02/30] include/exec/memop: Add bits describing atomicity Date: Tue, 28 Feb 2023 17:56:28 +0000 In-reply-to: <20230216025739.1211680-3-richard.henderson@linaro.org> Message-ID: <87v8jlekry.fsf@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Received-SPF: pass client-ip=2a00:1450:4864:20::32b; envelope-from=alex.bennee@linaro.org; helo=mail-wm1-x32b.google.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Richard Henderson writes: > These bits may be used to describe the precise atomicity > requirements of the guest, which may then be used to > constrain the methods by which it may be emulated by the host. > > For instance, the AArch64 LDP (32-bit) instruction changes > semantics with ARMv8.4 LSE2, from > > MO_64 | MO_ATMAX_4 | MO_ATOM_IFALIGN > (64-bits, single-copy atomic only on 4 byte units, > nonatomic if not aligned by 4), > > to > > MO_64 | MO_ATMAX_SIZE | MO_ATOM_WITHIN16 > (64-bits, single-copy atomic within a 16 byte block) > > The former may be implemented with two 4 byte loads, or > a single 8 byte load if that happens to be efficient on > the host. The latter may not, and may also require a > helper when misaligned. > > Signed-off-by: Richard Henderson Reviewed-by: Alex Benn=C3=A9e --=20 Alex Benn=C3=A9e Virtualisation Tech Lead @ Linaro