Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753941AbaLAOPA (ORCPT ); Mon, 1 Dec 2014 09:15:00 -0500 Received: from smtp.citrix.com ([66.165.176.89]:51593 "EHLO SMTP.CITRIX.COM" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753491AbaLAOO7 (ORCPT ); Mon, 1 Dec 2014 09:14:59 -0500 X-IronPort-AV: E=Sophos;i="5.07,494,1413244800"; d="scan'208";a="198075466" Message-ID: <547C77E0.5060607@citrix.com> Date: Mon, 1 Dec 2014 14:14:56 +0000 From: David Vrabel User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Icedove/31.2.0 MIME-Version: 1.0 To: Konrad Rzeszutek Wilk , , , , , Subject: Re: [Xen-devel] [PATCH v4 7/7] xen/pciback: Restore configuration space when detaching from a guest. References: <1416608271-18931-1-git-send-email-konrad.wilk@oracle.com> <1416608271-18931-8-git-send-email-konrad.wilk@oracle.com> In-Reply-To: <1416608271-18931-8-git-send-email-konrad.wilk@oracle.com> Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 8bit X-DLP: MIA1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 21/11/14 22:17, Konrad Rzeszutek Wilk wrote: > 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"); Why dev_info when... > @@ -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"); ... this one is dev_warn? > + else { > + __pci_reset_function_locked(dev); I think the reset should always be attempted regardless of whether the correct state was loaded or not. David -- 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/