From patchwork Mon Jan 23 12:17:10 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jonathan Cameron X-Patchwork-Id: 13112010 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id A2640C54E94 for ; Mon, 23 Jan 2023 12:17:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229502AbjAWMRR (ORCPT ); Mon, 23 Jan 2023 07:17:17 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54740 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231529AbjAWMRQ (ORCPT ); Mon, 23 Jan 2023 07:17:16 -0500 Received: from frasgout.his.huawei.com (frasgout.his.huawei.com [185.176.79.56]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1648023873 for ; Mon, 23 Jan 2023 04:17:14 -0800 (PST) Received: from lhrpeml500005.china.huawei.com (unknown [172.18.147.207]) by frasgout.his.huawei.com (SkyGuard) with ESMTP id 4P0pxG4ZF7z67tG2; Mon, 23 Jan 2023 20:16:34 +0800 (CST) Received: from SecurePC-101-06.china.huawei.com (10.122.247.231) by lhrpeml500005.china.huawei.com (7.191.163.240) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.34; Mon, 23 Jan 2023 12:17:12 +0000 From: Jonathan Cameron To: CC: Ben Widawsky , , , Ira Weiny , Dave Jiang , , Fan Ni Subject: [RFC PATCH 0/2] hw/cxl: Passthrough HDM decoder emulation Date: Mon, 23 Jan 2023 12:17:10 +0000 Message-ID: <20230123121712.29892-1-Jonathan.Cameron@huawei.com> X-Mailer: git-send-email 2.37.2 MIME-Version: 1.0 X-Originating-IP: [10.122.247.231] X-ClientProxiedBy: lhrpeml100002.china.huawei.com (7.191.160.241) To lhrpeml500005.china.huawei.com (7.191.163.240) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-cxl@vger.kernel.org Until now, testing using CXL has relied up always using two root ports below a host bridge, to work around a current assumption in the Linux kernel support that, in the single root port case, the implementation will use the allowed passthrough decoder implementation choice. If that choice is made all accesses are routed from the host bridge to the single root port that is present. Effectively we have a pass through decoder (it is called that in the kernel driver). This patch series implements that functionality and makes it the default See patch 2 for a discussion of why I think we can make this change without backwards compatibility issues (basically if it didn't work before who are we breaking by making it work?) Whilst this limitation has been known since the initial QEMU patch postings / kernel CXL region support, Fan Ni Ran into it recently reminding me that we should solve it. https://lore.kernel.org/linux-cxl/20230113171044.GA24788@bgt-140510-bm03/ Tree with a large set of patches before this at: https://gitlab.com/jic23/qemu/-/tree/cxl-2023-01-20 I've done some basic testing, though I did hit what appears to be a kernel race on region bring up of existing region / namespace in a 1HB 2RP 2EP test case. That is proving hard to replicate consistently but doesn't seem to have anything to do with the emulation other than perhaps we are opening up a race by responding slowly to something. Jonathan Cameron (2): hw/pci: Add pcie_count_ds_port() and pcie_find_port_first() helpers hw/pxb-cxl: Support passthrough HDM Decoders unless overridden hw/cxl/cxl-host.c | 31 +++++++++++++-------- hw/pci-bridge/pci_expander_bridge.c | 43 +++++++++++++++++++++++++---- hw/pci/pcie_port.c | 38 +++++++++++++++++++++++++ include/hw/cxl/cxl.h | 1 + include/hw/cxl/cxl_component.h | 1 + include/hw/pci/pci_bridge.h | 1 + include/hw/pci/pcie_port.h | 2 ++ 7 files changed, 100 insertions(+), 17 deletions(-)