From patchwork Mon Dec 16 22:16:54 2013 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Alex Williamson X-Patchwork-Id: 3357221 X-Patchwork-Delegate: bhelgaas@google.com Return-Path: X-Original-To: patchwork-linux-pci@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork1.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.19.201]) by patchwork1.web.kernel.org (Postfix) with ESMTP id 5FAFC9F380 for ; Mon, 16 Dec 2013 22:16:59 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 7FCA920257 for ; Mon, 16 Dec 2013 22:16:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 95B6720255 for ; Mon, 16 Dec 2013 22:16:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751088Ab3LPWQ4 (ORCPT ); Mon, 16 Dec 2013 17:16:56 -0500 Received: from mx1.redhat.com ([209.132.183.28]:44168 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751019Ab3LPWQz (ORCPT ); Mon, 16 Dec 2013 17:16:55 -0500 Received: from int-mx09.intmail.prod.int.phx2.redhat.com (int-mx09.intmail.prod.int.phx2.redhat.com [10.5.11.22]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id rBGMGthO009677 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK); Mon, 16 Dec 2013 17:16:55 -0500 Received: from bling.home (ovpn-113-110.phx2.redhat.com [10.3.113.110]) by int-mx09.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id rBGMGs62011483; Mon, 16 Dec 2013 17:16:55 -0500 Subject: [PATCH] vfio-pci: Use pci "try" reset interface To: alex.williamson@redhat.com From: Alex Williamson Cc: linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org Date: Mon, 16 Dec 2013 15:16:54 -0700 Message-ID: <20131216221615.3539.78656.stgit@bling.home> User-Agent: StGit/0.16 MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.68 on 10.5.11.22 Sender: linux-pci-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org X-Spam-Status: No, score=-7.4 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP PCI resets will attempt to take the device_lock for any device to be reset. This is a problem if that lock is already held, for instance in the device remove path. It's not sufficient to simply kill the user process or skip the reset if called after .remove as a race could result in the same deadlock. Instead, we handle all resets as "best effort" using the PCI "try" reset interfaces. This prevents the user from being able to induce a deadlock by triggering a reset. Signed-off-by: Alex Williamson --- This depends on the proposed pci "try" function/slot/bus reset patch. drivers/vfio/pci/vfio_pci.c | 29 +++++++++-------------------- 1 file changed, 9 insertions(+), 20 deletions(-) -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c index 6ab71b9..576e34e 100644 --- a/drivers/vfio/pci/vfio_pci.c +++ b/drivers/vfio/pci/vfio_pci.c @@ -139,25 +139,14 @@ static void vfio_pci_disable(struct vfio_pci_device *vdev) pci_write_config_word(pdev, PCI_COMMAND, PCI_COMMAND_INTX_DISABLE); /* - * Careful, device_lock may already be held. This is the case if - * a driver unbind is blocked. Try to get the locks ourselves to - * prevent a deadlock. + * Try to reset the device. The success of this is dependent on + * being able to lock the device, which is not always possible. */ if (vdev->reset_works) { - bool reset_done = false; - - if (pci_cfg_access_trylock(pdev)) { - if (device_trylock(&pdev->dev)) { - __pci_reset_function_locked(pdev); - reset_done = true; - device_unlock(&pdev->dev); - } - pci_cfg_access_unlock(pdev); - } - - if (!reset_done) - pr_warn("%s: Unable to acquire locks for reset of %s\n", - __func__, dev_name(&pdev->dev)); + int ret = pci_try_reset_function(pdev); + if (ret) + pr_debug("%s: reset of device %s = %d\n", + __func__, dev_name(&pdev->dev), ret); } pci_restore_state(pdev); @@ -514,7 +503,7 @@ static long vfio_pci_ioctl(void *device_data, } else if (cmd == VFIO_DEVICE_RESET) { return vdev->reset_works ? - pci_reset_function(vdev->pdev) : -EINVAL; + pci_try_reset_function(vdev->pdev) : -EINVAL; } else if (cmd == VFIO_DEVICE_GET_PCI_HOT_RESET_INFO) { struct vfio_pci_hot_reset_info hdr; @@ -684,8 +673,8 @@ reset_info_exit: &info, slot); if (!ret) /* User has access, do the reset */ - ret = slot ? pci_reset_slot(vdev->pdev->slot) : - pci_reset_bus(vdev->pdev->bus); + ret = slot ? pci_try_reset_slot(vdev->pdev->slot) : + pci_try_reset_bus(vdev->pdev->bus); hot_reset_release: for (i--; i >= 0; i--)