From mboxrd@z Thu Jan 1 00:00:00 1970 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=-6.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS 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 A64BAC3A5A0 for ; Mon, 19 Aug 2019 19:53:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 816E02087E for ; Mon, 19 Aug 2019 19:53:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728145AbfHSTxT (ORCPT ); Mon, 19 Aug 2019 15:53:19 -0400 Received: from mx1.redhat.com ([209.132.183.28]:58766 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727925AbfHSTxT (ORCPT ); Mon, 19 Aug 2019 15:53:19 -0400 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 63739308449A; Mon, 19 Aug 2019 19:53:19 +0000 (UTC) Received: from x1.home (ovpn-116-99.phx2.redhat.com [10.3.116.99]) by smtp.corp.redhat.com (Postfix) with ESMTP id C9F6C1CB; Mon, 19 Aug 2019 19:53:18 +0000 (UTC) Date: Mon, 19 Aug 2019 13:53:18 -0600 From: Alex Williamson To: hexin Cc: kvm@vger.kernel.org, linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, hexin , Liu Qi , Zhang Yu Subject: Re: [PATCH v2] vfio_pci: Replace pci_try_reset_function() with __pci_reset_function_locked() to ensure that the pci device configuration space is restored to its original state Message-ID: <20190819135318.72f64e0d@x1.home> In-Reply-To: <1566042663-16694-1-git-send-email-hexin15@baidu.com> References: <1566042663-16694-1-git-send-email-hexin15@baidu.com> Organization: Red Hat MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.40]); Mon, 19 Aug 2019 19:53:19 +0000 (UTC) Sender: linux-pci-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org On Sat, 17 Aug 2019 19:51:03 +0800 hexin wrote: > In vfio_pci_enable(), save the device's initial configuration information > and then restore the configuration in vfio_pci_disable(). However, the > execution result is not the same. Since the pci_try_reset_function() > function saves the current state before resetting, the configuration > information restored by pci_load_and_free_saved_state() will be > overwritten. The __pci_reset_function_locked() function can be used > to prevent the configuration space from being overwritten. > > Fixes: 890ed578df82 ("vfio-pci: Use pci "try" reset interface") > Signed-off-by: hexin > Signed-off-by: Liu Qi > Signed-off-by: Zhang Yu > --- > drivers/vfio/pci/vfio_pci.c | 17 +++++++++++++---- > 1 file changed, 13 insertions(+), 4 deletions(-) This looks good, but the subject is too long and I find the commit log somewhat confusing. May I update these as follows? vfio_pci: Restore original state on release vfio_pci_enable() saves the device's initial configuration information with the intent that it is restored in vfio_pci_disable(). However, commit 890ed578df82 ("vfio-pci: Use pci "try" reset interface") replaced the call to __pci_reset_function_locked(), which is not wrapped in a state save and restore, with pci_try_reset_function(), which overwrites the restored device state with the current state before applying it to the device. Restore use of __pci_reset_function_locked() to return to the desired behavior. Thanks, Alex > diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c > index 703948c..0220616 100644 > --- a/drivers/vfio/pci/vfio_pci.c > +++ b/drivers/vfio/pci/vfio_pci.c > @@ -438,11 +438,20 @@ static void vfio_pci_disable(struct vfio_pci_device *vdev) > pci_write_config_word(pdev, PCI_COMMAND, PCI_COMMAND_INTX_DISABLE); > > /* > - * Try to reset the device. The success of this is dependent on > - * being able to lock the device, which is not always possible. > + * Try to get the locks ourselves to prevent a deadlock. The > + * success of this is dependent on being able to lock the device, > + * which is not always possible. > + * We can not use the "try" reset interface here, which will > + * overwrite the previously restored configuration information. > */ > - if (vdev->reset_works && !pci_try_reset_function(pdev)) > - vdev->needs_reset = false; > + if (vdev->reset_works && pci_cfg_access_trylock(pdev)) { > + if (device_trylock(&pdev->dev)) { > + if (!__pci_reset_function_locked(pdev)) > + vdev->needs_reset = false; > + device_unlock(&pdev->dev); > + } > + pci_cfg_access_unlock(pdev); > + } > > pci_restore_state(pdev); > out: