Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752791AbaKUWSm (ORCPT ); Fri, 21 Nov 2014 17:18:42 -0500 Received: from aserp1040.oracle.com ([141.146.126.69]:34047 "EHLO aserp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752437AbaKUWSD (ORCPT ); Fri, 21 Nov 2014 17:18:03 -0500 From: Konrad Rzeszutek Wilk To: xen-devel@lists.xenproject.org, linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org, bhelgaas@google.com, linux@eikelenboom.it Cc: Konrad Rzeszutek Wilk Subject: [PATCH v4 7/7] xen/pciback: Restore configuration space when detaching from a guest. Date: Fri, 21 Nov 2014 17:17:51 -0500 Message-Id: <1416608271-18931-8-git-send-email-konrad.wilk@oracle.com> X-Mailer: git-send-email 1.9.3 In-Reply-To: <1416608271-18931-1-git-send-email-konrad.wilk@oracle.com> References: <1416608271-18931-1-git-send-email-konrad.wilk@oracle.com> X-Source-IP: acsinet22.oracle.com [141.146.126.238] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The commit "xen/pciback: Don't deadlock when unbinding." was using the version of pci_reset_function which would lock the device lock. That is no good as we can dead-lock. As such we swapped to using the lock-less version and requiring that the callers of 'pcistub_put_pci_dev' take the device lock. And as such this bug got exposed. Using the lock-less version is OK, except that we tried to use 'pci_restore_state' after the lock-less version of __pci_reset_function_locked - which won't work as 'state_saved' is set to false. Said 'state_saved' is a toggle boolean that is to be used by the sequence of a) pci_save_state/pci_restore_state or b) pci_load_and_free_saved_state/pci_restore_state. We don't want to use a) as the guest might have messed up the PCI configuration space and we want it to revert to the state when the PCI device was binded to us. Therefore we pick b) to restore the configuration space. We restore from our 'golden' version of PCI configuration space, when an: - Device is unbinded from pciback - Device is detached from a guest. Reported-by: Sander Eikelenboom Signed-off-by: Konrad Rzeszutek Wilk --- drivers/xen/xen-pciback/pci_stub.c | 20 ++++++++++++++++---- 1 file changed, 16 insertions(+), 4 deletions(-) diff --git a/drivers/xen/xen-pciback/pci_stub.c b/drivers/xen/xen-pciback/pci_stub.c index 843a2ba..eb8b58e 100644 --- a/drivers/xen/xen-pciback/pci_stub.c +++ b/drivers/xen/xen-pciback/pci_stub.c @@ -105,7 +105,7 @@ static void pcistub_device_release(struct kref *kref) */ __pci_reset_function_locked(dev); if (pci_load_and_free_saved_state(dev, &dev_data->pci_saved_state)) - dev_dbg(&dev->dev, "Could not reload PCI state\n"); + dev_info(&dev->dev, "Could not reload PCI state\n"); else pci_restore_state(dev); @@ -257,6 +257,8 @@ void pcistub_put_pci_dev(struct pci_dev *dev) { struct pcistub_device *psdev, *found_psdev = NULL; unsigned long flags; + struct xen_pcibk_dev_data *dev_data; + int ret; spin_lock_irqsave(&pcistub_devices_lock, flags); @@ -279,9 +281,19 @@ void pcistub_put_pci_dev(struct pci_dev *dev) * (so it's ready for the next domain) */ device_lock_assert(&dev->dev); - __pci_reset_function_locked(dev); - pci_restore_state(dev); - + dev_data = pci_get_drvdata(dev); + ret = pci_load_saved_state(dev, dev_data->pci_saved_state); + if (ret < 0) + dev_warn(&dev->dev, "Could not reload PCI state\n"); + else { + __pci_reset_function_locked(dev); + /* + * The usual sequence is pci_save_state & pci_restore_state + * but the guest might have messed the configuration space up. + * Use the initial version (when device was bound to us). + */ + pci_restore_state(dev); + } /* This disables the device. */ xen_pcibk_reset_device(dev); -- 1.9.3 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/