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 D03E3C433F5 for ; Wed, 2 Mar 2022 13:08:26 +0000 (UTC) Received: from localhost ([::1]:33194 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1nPOiP-0006FC-DP for qemu-devel@archiver.kernel.org; Wed, 02 Mar 2022 08:08:25 -0500 Received: from eggs.gnu.org ([209.51.188.92]:45050) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1nPNuh-0000ci-Uu for qemu-devel@nongnu.org; Wed, 02 Mar 2022 07:17:04 -0500 Received: from [2a00:1450:4864:20::62a] (port=43750 helo=mail-ej1-x62a.google.com) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1nPNuf-0001Rh-R3 for qemu-devel@nongnu.org; Wed, 02 Mar 2022 07:17:03 -0500 Received: by mail-ej1-x62a.google.com with SMTP id d10so3291631eje.10 for ; Wed, 02 Mar 2022 04:16:59 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=references:user-agent:from:to:cc:subject:date:in-reply-to :message-id:mime-version:content-transfer-encoding; bh=/84AvN/V83Oq1qZvODm1Fitth6dVROGE3KJULt/rHIU=; b=HpEBHuANEXVPI3QwoIH+rLLe9O/rvn9WzHl4I4vxC+rAj9Q2W94G2Gwanldwr3acs3 2wXJNu0sCAnRw74sjWvqtH8YKF80XYaGLoHLdIJUV0wuKjykMlhwtP/COatoGKZUHwFh VRdCI+yqVLQfw138Oyw3txw9xdT9XbyHFgWNYa4qn2Bhd9jJQO4eIObT6nOoMn6aaSkT ehC9+yrjWwQ7y21PK7JWPhcirx6qxe5fY4o+WZGj3oSWQ9N1KoVoQBFzIlhLF8L56P3p wm25ouCm13LvgVoXRJ5JntvsiPxL1p9UPY4qDe3gkpGeWezjgojkfVN+fv09DEBTIw9a P1Dg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:references:user-agent:from:to:cc:subject:date :in-reply-to:message-id:mime-version:content-transfer-encoding; bh=/84AvN/V83Oq1qZvODm1Fitth6dVROGE3KJULt/rHIU=; b=WmtOZ6AS3AZ+22Nuu/is1APx6xNbFOkkBZWuyWFhPhAT9ydidN9BDUU/S+2oYhUIfJ zdGn0qX0HDk1H30yYyMpmEArXRsUe1WYna7XeW+hPMMHCA8ssS38zTp2oGFbms92tqib SBDj+sn2X+2DIq1/agHiMQ9NMmL9OW16ioklYJqoLAl7OLRXiNjZs51UUcoIG+BAA8N4 voYN8xr/s1DCHTphwnK6/oQ1XPWPaucBwlZI4Onbb7LtWCiSIHnU8NRRwqtK02t78UM6 NHn8vAjxlqX61d60tnrLrR7VwUlHKAwSwIEhRXXHMiwyuk0xyyq24KCde7L0w2wPkAUj +sVw== X-Gm-Message-State: AOAM532QlHytyDoSul3aQbMz3vZaQ9yW0XdcUuKwMqAPW9x6B/aS0y0H aRykhYJ+dqhz5J0F1WoOdKv5MQ== X-Google-Smtp-Source: ABdhPJzyb8qNK78797w/gXMaIuX6BOJSFa4o0M//VStsYBxdVWN024aMfnRXfLONMHXVf78ZmKwyDQ== X-Received: by 2002:a17:907:9898:b0:6cd:ed45:1123 with SMTP id ja24-20020a170907989800b006cded451123mr23613605ejc.155.1646223417953; Wed, 02 Mar 2022 04:16:57 -0800 (PST) Received: from zen.linaroharston ([51.148.130.216]) by smtp.gmail.com with ESMTPSA id f5-20020a1709067f8500b006da68bfdfc7sm399202ejr.12.2022.03.02.04.16.56 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 02 Mar 2022 04:16:56 -0800 (PST) Received: from zen (localhost [127.0.0.1]) by zen.linaroharston (Postfix) with ESMTP id E9D481FFB7; Wed, 2 Mar 2022 12:16:55 +0000 (GMT) References: <20220211120747.3074-1-Jonathan.Cameron@huawei.com> <20220211120747.3074-26-Jonathan.Cameron@huawei.com> User-agent: mu4e 1.7.9; emacs 28.0.91 From: Alex =?utf-8?Q?Benn=C3=A9e?= To: Jonathan Cameron Subject: Re: [PATCH v6 25/43] acpi/cxl: Create the CEDT (9.14.1) Date: Wed, 02 Mar 2022 12:16:48 +0000 In-reply-to: <20220211120747.3074-26-Jonathan.Cameron@huawei.com> Message-ID: <87k0dck0qw.fsf@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Host-Lookup-Failed: Reverse DNS lookup failed for 2a00:1450:4864:20::62a (failed) Received-SPF: pass client-ip=2a00:1450:4864:20::62a; envelope-from=alex.bennee@linaro.org; helo=mail-ej1-x62a.google.com X-Spam_score_int: -6 X-Spam_score: -0.7 X-Spam_bar: / X-Spam_report: (-0.7 / 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, PDS_HP_HELO_NORDNS=0.659, RCVD_IN_DNSWL_NONE=-0.0001, RDNS_NONE=0.793, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=no 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: , Cc: Peter Maydell , Ben Widawsky , "Michael S . Tsirkin" , Samarth Saxena , Chris Browy , qemu-devel@nongnu.org, linux-cxl@vger.kernel.org, linuxarm@huawei.com, Shreyas Shah , Saransh Gupta1 , Shameerali Kolothum Thodi , Marcel Apfelbaum , Igor Mammedov , Dan Williams , Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Jonathan Cameron writes: > From: Ben Widawsky > > The CXL Early Discovery Table is defined in the CXL 2.0 specification as > a way for the OS to get CXL specific information from the system > firmware. > > CXL 2.0 specification adds an _HID, ACPI0016, for CXL capable host > bridges, with a _CID of PNP0A08 (PCIe host bridge). CXL aware software > is able to use this initiate the proper _OSC method, and get the _UID > which is referenced by the CEDT. Therefore the existence of an ACPI0016 > device allows a CXL aware driver perform the necessary actions. For a > CXL capable OS, this works. For a CXL unaware OS, this works. > > CEDT awaremess requires more. The motivation for ACPI0017 is to provide > the possibility of having a Linux CXL module that can work on a legacy > Linux kernel. Linux core PCI/ACPI which won't be built as a module, > will see the _CID of PNP0A08 and bind a driver to it. If we later loaded > a driver for ACPI0016, Linux won't be able to bind it to the hardware > because it has already bound the PNP0A08 driver. The ACPI0017 device is > an opportunity to have an object to bind a driver will be used by a > Linux driver to walk the CXL topology and do everything that we would > have preferred to do with ACPI0016. > > There is another motivation for an ACPI0017 device which isn't > implemented here. An operating system needs an attach point for a > non-volatile region provider that understands cross-hostbridge > interleaving. Since QEMU emulation doesn't support interleaving yet, > this is more important on the OS side, for now. > > As of CXL 2.0 spec, only 1 sub structure is defined, the CXL Host Bridge > Structure (CHBS) which is primarily useful for telling the OS exactly > where the MMIO for the host bridge is. > > Link: https://lore.kernel.org/linux-cxl/20210115034911.nkgpzc756d6qmjpl@i= ntel.com/T/#t > Signed-off-by: Ben Widawsky > Signed-off-by: Jonathan Cameron Reviewed-by: Alex Benn=C3=A9e --=20 Alex Benn=C3=A9e