From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alex Williamson Subject: [PATCH 3/3] vfio-pci: Avoid deadlock on remove Date: Tue, 11 Jun 2013 10:01:54 -0600 Message-ID: <20130611160154.9995.5152.stgit@bling.home> References: <20130611155848.9995.41709.stgit@bling.home> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org To: alex.williamson@redhat.com Return-path: Received: from mx1.redhat.com ([209.132.183.28]:45955 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751808Ab3FKQBz (ORCPT ); Tue, 11 Jun 2013 12:01:55 -0400 In-Reply-To: <20130611155848.9995.41709.stgit@bling.home> Sender: kvm-owner@vger.kernel.org List-ID: If an attempt is made to unbind a device from vfio-pci while that device is in use, the request is blocked until the device becomes unused. Unfortunately, that unbind path still grabs the device_lock, which certain things like __pci_reset_function() also want to take. This means we need to try to acquire the locks ourselves and use the pre-locked version, __pci_reset_function_locked(). Signed-off-by: Alex Williamson --- drivers/vfio/pci/vfio_pci.c | 23 +++++++++++++++++++++-- 1 file changed, 21 insertions(+), 2 deletions(-) diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c index ac37254..41023e4 100644 --- a/drivers/vfio/pci/vfio_pci.c +++ b/drivers/vfio/pci/vfio_pci.c @@ -137,8 +137,27 @@ static void vfio_pci_disable(struct vfio_pci_device *vdev) */ pci_write_config_word(pdev, PCI_COMMAND, PCI_COMMAND_INTX_DISABLE); - if (vdev->reset_works) - __pci_reset_function(pdev); + /* + * 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. + */ + 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)); + } pci_restore_state(pdev); }