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 X-Spam-Level: X-Spam-Status: No, score=-20.2 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 08672C12002 for ; Mon, 19 Jul 2021 17:11:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D0B5F6023F for ; Mon, 19 Jul 2021 17:11:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1350448AbhGSQ33 (ORCPT ); Mon, 19 Jul 2021 12:29:29 -0400 Received: from mail.kernel.org ([198.145.29.99]:56374 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1347367AbhGSPQG (ORCPT ); Mon, 19 Jul 2021 11:16:06 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id F059B60FDA; Mon, 19 Jul 2021 15:56:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1626710204; bh=qfTRyoMxz6dWPn/7RMp+HaHSUxHIEGIeUWhQntLvNrs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=XqV35ROIHVFyADay4aYTWICPaCVgUnoKDSY0bj9Amcw+beLfIrntkWooqqp9vBbL9 NOjuTR+LloOvFu5Mtnxr+awrlLqpZl0dPdegxX9O0vePX3x7MTnqvculht2YKUBnSh bejBM4Qgwq36/QbeUuDR5cfHzOPY2QvwaOcxOBH0= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Logan Gunthorpe , Bjorn Helgaas , Sasha Levin Subject: [PATCH 5.10 120/243] PCI/P2PDMA: Avoid pci_get_slot(), which may sleep Date: Mon, 19 Jul 2021 16:52:29 +0200 Message-Id: <20210719144944.788940640@linuxfoundation.org> X-Mailer: git-send-email 2.32.0 In-Reply-To: <20210719144940.904087935@linuxfoundation.org> References: <20210719144940.904087935@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Logan Gunthorpe [ Upstream commit 3ec0c3ec2d92c09465534a1ff9c6f9d9506ffef6 ] In order to use upstream_bridge_distance_warn() from a dma_map function, it must not sleep. However, pci_get_slot() takes the pci_bus_sem so it might sleep. In order to avoid this, try to get the host bridge's device from the first element in the device list. It should be impossible for the host bridge's device to go away while references are held on child devices, so the first element should not be able to change and, thus, this should be safe. Introduce a static function called pci_host_bridge_dev() to obtain the host bridge's root device. Link: https://lore.kernel.org/r/20210610160609.28447-7-logang@deltatee.com Signed-off-by: Logan Gunthorpe Signed-off-by: Bjorn Helgaas Signed-off-by: Sasha Levin --- drivers/pci/p2pdma.c | 34 ++++++++++++++++++++++++++++++++-- 1 file changed, 32 insertions(+), 2 deletions(-) diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c index de1c331dbed4..f07c5dbc94e1 100644 --- a/drivers/pci/p2pdma.c +++ b/drivers/pci/p2pdma.c @@ -308,10 +308,41 @@ static const struct pci_p2pdma_whitelist_entry { {} }; +/* + * This lookup function tries to find the PCI device corresponding to a given + * host bridge. + * + * It assumes the host bridge device is the first PCI device in the + * bus->devices list and that the devfn is 00.0. These assumptions should hold + * for all the devices in the whitelist above. + * + * This function is equivalent to pci_get_slot(host->bus, 0), however it does + * not take the pci_bus_sem lock seeing __host_bridge_whitelist() must not + * sleep. + * + * For this to be safe, the caller should hold a reference to a device on the + * bridge, which should ensure the host_bridge device will not be freed + * or removed from the head of the devices list. + */ +static struct pci_dev *pci_host_bridge_dev(struct pci_host_bridge *host) +{ + struct pci_dev *root; + + root = list_first_entry_or_null(&host->bus->devices, + struct pci_dev, bus_list); + + if (!root) + return NULL; + if (root->devfn != PCI_DEVFN(0, 0)) + return NULL; + + return root; +} + static bool __host_bridge_whitelist(struct pci_host_bridge *host, bool same_host_bridge) { - struct pci_dev *root = pci_get_slot(host->bus, PCI_DEVFN(0, 0)); + struct pci_dev *root = pci_host_bridge_dev(host); const struct pci_p2pdma_whitelist_entry *entry; unsigned short vendor, device; @@ -320,7 +351,6 @@ static bool __host_bridge_whitelist(struct pci_host_bridge *host, vendor = root->vendor; device = root->device; - pci_dev_put(root); for (entry = pci_p2pdma_whitelist; entry->vendor; entry++) { if (vendor != entry->vendor || device != entry->device) -- 2.30.2