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=unavailable 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 A7E61C3A59C for ; Fri, 16 Aug 2019 15:24:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 83E49206C1 for ; Fri, 16 Aug 2019 15:24:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727551AbfHPPYR (ORCPT ); Fri, 16 Aug 2019 11:24:17 -0400 Received: from mx1.redhat.com ([209.132.183.28]:45478 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727217AbfHPPYR (ORCPT ); Fri, 16 Aug 2019 11:24:17 -0400 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 76173300CB2B; Fri, 16 Aug 2019 15:24:17 +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 A30BA3786; Fri, 16 Aug 2019 15:24:16 +0000 (UTC) Date: Fri, 16 Aug 2019 09:24:15 -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] 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: <20190816092415.1b05aa0a@x1.home> In-Reply-To: <1565926427-21675-1-git-send-email-hexin15@baidu.com> References: <1565926427-21675-1-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 10.5.11.15 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.46]); Fri, 16 Aug 2019 15:24:17 +0000 (UTC) Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Fri, 16 Aug 2019 11:33:47 +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. > > Signed-off-by: hexin > Signed-off-by: Liu Qi > Signed-off-by: Zhang Yu > --- > drivers/vfio/pci/vfio_pci.c | 10 ++++++++-- > 1 file changed, 8 insertions(+), 2 deletions(-) > > diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c > index 703948c..3c93492 100644 > --- a/drivers/vfio/pci/vfio_pci.c > +++ b/drivers/vfio/pci/vfio_pci.c > @@ -441,8 +441,14 @@ static void vfio_pci_disable(struct vfio_pci_device *vdev) > * 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 && !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: This used to work, I think what happened is that we initially called __pci_reset_function() to avoid the saved state getting overwritten, then commit d24cdbfd28b7 ("vfio-pci: Avoid deadlock on remove") added the trylock support to avoid deadlock, then commit 890ed578df82 ("vfio-pci: Use pci "try" reset interface") assumed the trylock was the reason for the unusual calling convention and simply replaced it with pci_try_reset_function(). So, I think we need two things. First, a fixes tag: Fixes: 890ed578df82 ("vfio-pci: Use pci "try" reset interface") Second, a comment to warn us against performing a similar cleanup again in the future. Thanks, Alex