From patchwork Fri Dec 18 17:39:46 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sergei Miroshnichenko X-Patchwork-Id: 11982637 X-Patchwork-Delegate: bhelgaas@google.com 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=-18.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_GIT autolearn=ham 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 E8960C2BBD5 for ; Fri, 18 Dec 2020 17:42:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B2ABD23B7D for ; Fri, 18 Dec 2020 17:42:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731636AbgLRRlv (ORCPT ); Fri, 18 Dec 2020 12:41:51 -0500 Received: from mta-02.yadro.com ([89.207.88.252]:37876 "EHLO mta-01.yadro.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726057AbgLRRlv (ORCPT ); Fri, 18 Dec 2020 12:41:51 -0500 Received: from localhost (unknown [127.0.0.1]) by mta-01.yadro.com (Postfix) with ESMTP id 05733413C8; Fri, 18 Dec 2020 17:41:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=yadro.com; h= content-type:content-type:content-transfer-encoding:mime-version :references:in-reply-to:x-mailer:message-id:date:date:subject :subject:from:from:received:received:received; s=mta-01; t= 1608313267; x=1610127668; bh=vlhDGWs84jnDn9lker3XX/X6kdDT1STUvKr Mzdw7AQ0=; b=U2inflNqwtIgmlPeeDSyU5RoTBZUcUjrVs540Tuc2ntT6K25n4a X92sRuCyjJBeO5OwqC59Bg4iBMwxIkCab36FcGRDTwXNaTnkHF6wh/8+UZsegkx4 i6YzxyjVbzlRiZZMqTh2Q9P6kog+Z9+vaNqCntABo9zmwql7zWy2a7Ng= X-Virus-Scanned: amavisd-new at yadro.com Received: from mta-01.yadro.com ([127.0.0.1]) by localhost (mta-01.yadro.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id t1wUiKuRBgiS; Fri, 18 Dec 2020 20:41:07 +0300 (MSK) Received: from T-EXCH-03.corp.yadro.com (t-exch-03.corp.yadro.com [172.17.100.103]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-SHA384 (256/256 bits)) (No client certificate requested) by mta-01.yadro.com (Postfix) with ESMTPS id 6D9F34137C; Fri, 18 Dec 2020 20:41:06 +0300 (MSK) Received: from NB-148.yadro.com (172.17.15.136) by T-EXCH-03.corp.yadro.com (172.17.100.103) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384_P384) id 15.1.669.32; Fri, 18 Dec 2020 20:41:05 +0300 From: Sergei Miroshnichenko To: CC: Bjorn Helgaas , Lukas Wunner , Stefan Roese , Andy Lavr , =?utf-8?q?Chris?= =?utf-8?q?tian_K=C3=B6nig?= , David Laight , Rajat Jain , , Sergei Miroshnichenko , Srinath Mannam , Marta Rybczynska Subject: [PATCH v9 01/26] PCI: Fix race condition in pci_enable/disable_device() Date: Fri, 18 Dec 2020 20:39:46 +0300 Message-ID: <20201218174011.340514-2-s.miroshnichenko@yadro.com> X-Mailer: git-send-email 2.24.1 In-Reply-To: <20201218174011.340514-1-s.miroshnichenko@yadro.com> References: <20201218174011.340514-1-s.miroshnichenko@yadro.com> MIME-Version: 1.0 X-Originating-IP: [172.17.15.136] X-ClientProxiedBy: T-EXCH-01.corp.yadro.com (172.17.10.101) To T-EXCH-03.corp.yadro.com (172.17.100.103) Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org This is a yet another approach to fix an old [1-2] concurrency issue, when: - two or more devices are being hot-added into a bridge which was initially empty; - a bridge with two or more devices is being hot-added; - the BIOS/bootloader/firmware doesn't pre-enable bridges during boot; The problem is that a bridge is reported as enabled before the MEM/IO bits are actually written to the PCI_COMMAND register, so another driver thread starts memory requests through the not-yet-enabled bridge: CPU0 CPU1 pci_enable_device_mem() pci_enable_device_mem() pci_enable_bridge() pci_enable_bridge() pci_is_enabled() return false; atomic_inc_return(enable_cnt) Start actual enabling the bridge ... pci_is_enabled() ... return true; ... Start memory requests <-- FAIL ... Set the PCI_COMMAND_MEMORY bit <-- Must wait for this Protect the pci_enable_bridge(), similarly to the previous solution from commit 40f11adc7cd9 ("PCI: Avoid race while enabling upstream bridges"), but adding per-device mutexes. To prevent false positives from the lockdep, use a lock_nested() with a "depth" of a bridge within the PCI topology. CC: Srinath Mannam CC: Marta Rybczynska Signed-off-by: Sergei Miroshnichenko [1] https://lore.kernel.org/linux-pci/1501858648-22228-1-git-send-email-srinath.mannam@broadcom.com/T/#u [RFC PATCH v3] pci: Concurrency issue during pci enable bridge [2] https://lore.kernel.org/linux-pci/744877924.5841545.1521630049567.JavaMail.zimbra@kalray.eu/T/#u [RFC PATCH] nvme: avoid race-conditions when enabling devices --- drivers/pci/pci.c | 16 ++++++++++++++++ drivers/pci/probe.c | 1 + include/linux/pci.h | 1 + 3 files changed, 18 insertions(+) diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c index b9fecc25d213..076b908127fe 100644 --- a/drivers/pci/pci.c +++ b/drivers/pci/pci.c @@ -1844,11 +1844,25 @@ int pci_reenable_device(struct pci_dev *dev) } EXPORT_SYMBOL(pci_reenable_device); +#ifdef CONFIG_PROVE_LOCKING +static int pci_bridge_depth(struct pci_dev *dev) +{ + struct pci_dev *bridge = pci_upstream_bridge(dev); + + if (!bridge) + return 0; + + return 1 + pci_bridge_depth(bridge); +} +#endif /* CONFIG_PROVE_LOCKING */ + static void pci_enable_bridge(struct pci_dev *dev) { struct pci_dev *bridge; int retval; + mutex_lock_nested(&dev->enable_mutex, pci_bridge_depth(dev)); + bridge = pci_upstream_bridge(dev); if (bridge) pci_enable_bridge(bridge); @@ -1856,6 +1870,7 @@ static void pci_enable_bridge(struct pci_dev *dev) if (pci_is_enabled(dev)) { if (!dev->is_busmaster) pci_set_master(dev); + mutex_unlock(&dev->enable_mutex); return; } @@ -1864,6 +1879,7 @@ static void pci_enable_bridge(struct pci_dev *dev) pci_err(dev, "Error enabling bridge (%d), continuing\n", retval); pci_set_master(dev); + mutex_unlock(&dev->enable_mutex); } static int pci_enable_device_flags(struct pci_dev *dev, unsigned long flags) diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c index 953f15abc850..2f9631287719 100644 --- a/drivers/pci/probe.c +++ b/drivers/pci/probe.c @@ -2240,6 +2240,7 @@ struct pci_dev *pci_alloc_dev(struct pci_bus *bus) INIT_LIST_HEAD(&dev->bus_list); dev->dev.type = &pci_dev_type; dev->bus = pci_bus_get(bus); + mutex_init(&dev->enable_mutex); return dev; } diff --git a/include/linux/pci.h b/include/linux/pci.h index b32126d26997..81d54889bd51 100644 --- a/include/linux/pci.h +++ b/include/linux/pci.h @@ -455,6 +455,7 @@ struct pci_dev { unsigned int no_command_memory:1; /* No PCI_COMMAND_MEMORY */ pci_dev_flags_t dev_flags; atomic_t enable_cnt; /* pci_enable_device has been called */ + struct mutex enable_mutex; u32 saved_config_space[16]; /* Config space saved at suspend time */ struct hlist_head saved_cap_space;