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, URIBL_BLOCKED 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 B95D4C3A59E for ; Wed, 21 Aug 2019 16:39:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8B8D42339E for ; Wed, 21 Aug 2019 16:39:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729358AbfHUQjT convert rfc822-to-8bit (ORCPT ); Wed, 21 Aug 2019 12:39:19 -0400 Received: from mx1.redhat.com ([209.132.183.28]:33608 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727037AbfHUQjT (ORCPT ); Wed, 21 Aug 2019 12:39:19 -0400 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 63935315C007; Wed, 21 Aug 2019 16:39:18 +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 B0A6810016E9; Wed, 21 Aug 2019 16:39:17 +0000 (UTC) Date: Wed, 21 Aug 2019 10:39:17 -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: <20190821103917.43487a1d@x1.home> In-Reply-To: References: <1566042663-16694-1-git-send-email-hexin15@baidu.com> <20190819135318.72f64e0d@x1.home> Organization: Red Hat MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.41]); Wed, 21 Aug 2019 16:39:18 +0000 (UTC) Sender: linux-pci-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org On Wed, 21 Aug 2019 23:13:08 +0800 hexin wrote: > Alex Williamson 于2019年8月20日周二 上午3:53写道： > > > > 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 > > > > > > Thanks for your update, the updated commit log is clearer than before. > At the same time, when I use checkpatch.pl to detect the patch, there > will be the > following error: > > ERROR: Please use git commit description style 'commit <12+ chars of > sha1> ("")' > - ie: 'commit 890ed578df82 ("vfio-pci: Use pci "try" reset interface")' > > Line 2785 ~ 2801 in checkpatch.pl, the script can't handle the commit message > which contains double quotes because of the expression `([^"]+)`. Like > the "try" above. > Maybe checkpatch.pl needs to be modified. I think we're following the intention of the rule, and as you've identified it's the implementation of the rule checker that's unable to handle a commit title with internal quotes. We can ignore it, and maybe follow up with a checkpatch.pl patch, or we could just avoid it 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, the commit referenced in Fixes: below 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. Reinstate 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: > >