From patchwork Thu Mar 7 23:04:32 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Dave Jiang X-Patchwork-Id: 13586329 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 90F873D0D2 for ; Thu, 7 Mar 2024 23:04:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1709852694; cv=none; b=NzhB3Wk8K8XzP/rLmGFuCPeZil3FMEtGsAttSmJWcTmCAdYAmBlH6/iUJtAg5H0EosUyvuZNbmr/7hV8lL6M/iz/1/cBRnfB8gNFkxd65Rv1d/DK+ULJC9TAIAAhUWh0qPjUtfq5TWK5s/4CxZeGl7VSLnPwh5Mgw0LfC8pjg2M= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1709852694; c=relaxed/simple; bh=MVTgmyzFIA855qrUQe3+aKzN1feXA7Luq0yDtxFqTBQ=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=c9j1FnmHOI0GvHfR2+jJrKJzatYIAmt5t8iW5iwFdhSTDJ2qhVrTwU6td8KSfxAYDWm0W0pJJkVkH2cJyKTNIrCl0NbYgnRHEC65ucMMUfSa4Op0UkKZzuc4pLkZXhTGchhEittK/fmHHY9nAyWZ+MmkGeJsJ+ttwPoVw2oLBpE= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1ADBCC433F1; Thu, 7 Mar 2024 23:04:52 +0000 (UTC) From: Dave Jiang To: linux-cxl@vger.kernel.org Cc: dan.j.williams@intel.com, ira.weiny@intel.com, vishal.l.verma@intel.com, alison.schofield@intel.com, Jonathan.Cameron@huawei.com, dave@stgolabs.net Subject: [PATCH v4 3/3] cxl: Add checks to access_coordinate calculation to fail missing data Date: Thu, 7 Mar 2024 16:04:32 -0700 Message-ID: <20240307230432.2006490-3-dave.jiang@intel.com> X-Mailer: git-send-email 2.44.0 In-Reply-To: <20240307230432.2006490-1-dave.jiang@intel.com> References: <20240307230432.2006490-1-dave.jiang@intel.com> Precedence: bulk X-Mailing-List: linux-cxl@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Jonathan noted that when the coordinates for host bridge and switches can be 0s if no actual data are retrieved and the calculation continues. The resulting number would be inaccurate. Add checks to ensure that the calculation would complete only if the numbers are valid. While not seen in the wild, issue may show up with a BIOS that reported CXL root ports via Generic Ports (via a PCI handle in the SRAT entry). Fixes: 14a6960b3e92 ("cxl: Add helper function that calculate performance data for downstream ports") Reported-by: Jonathan Cameron Reviewed-by: Jonathan Cameron Signed-off-by: Dave Jiang --- v4: - Flip coordinates_invalid() to coordinates_valid(). (Jonathan) --- drivers/cxl/core/port.c | 30 ++++++++++++++++++++---------- 1 file changed, 20 insertions(+), 10 deletions(-) diff --git a/drivers/cxl/core/port.c b/drivers/cxl/core/port.c index 6fa273677963..c3f3d153ee23 100644 --- a/drivers/cxl/core/port.c +++ b/drivers/cxl/core/port.c @@ -2110,6 +2110,17 @@ static void combine_coordinates(struct access_coordinate *c1, c1->read_latency += c2->read_latency; } +static bool coordinates_valid(struct access_coordinate *c) +{ + return c->read_bandwidth && c->write_bandwidth && + c->read_latency && c->write_latency; +} + +static bool parent_port_is_cxl_root(struct cxl_port *port) +{ + return is_cxl_root(to_cxl_port(port->dev.parent)); +} + /** * cxl_endpoint_get_perf_coordinates - Retrieve performance numbers stored in dports * of CXL path @@ -2133,23 +2144,22 @@ int cxl_endpoint_get_perf_coordinates(struct cxl_port *port, if (!is_cxl_endpoint(port)) return -EINVAL; - dport = iter->parent_dport; - /* - * Exit the loop when the parent port of the current port is cxl root. - * The iterative loop starts at the endpoint and gathers the - * latency of the CXL link from the current iter to the next downstream - * port each iteration. If the parent is cxl root then there is - * nothing to gather. + * Exit the loop when the parent port of the current iter port is cxl + * root. The iterative loop starts at the endpoint and gathers the + * latency of the CXL link from the current device/port to the connected + * downstream port each iteration. */ - while (!is_cxl_root(to_cxl_port(iter->dev.parent))) { + do { + dport = iter->parent_dport; + if (!coordinates_valid(&dport->coord)) + return -EINVAL; combine_coordinates(&c, &dport->coord); c.write_latency += dport->link_latency; c.read_latency += dport->link_latency; iter = to_cxl_port(iter->dev.parent); - dport = iter->parent_dport; - } + } while (!parent_port_is_cxl_root(iter)); /* Get the calculated PCI paths bandwidth */ pdev = to_pci_dev(port->uport_dev->parent);