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=-8.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,URIBL_BLOCKED,USER_AGENT_MUTT 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 75FAFC282CE for ; Fri, 5 Apr 2019 22:33:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3480321855 for ; Fri, 5 Apr 2019 22:33:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1554503587; bh=7ewTkUrqrMaQHlGYWysY7oJ/SHY7xljwl2B1977CleM=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=hYPhvvU6yqPbmdQ/lgoG7NlloRM6KYzgOuIXo+awuE2jvOi9YAbdz7KUSvpy5SS4t 1TPD2srYJIsf/6Oj3N/EYv0SyWcMZxBSLsYWoUx/Pr7goOX/BpUy4BG1vWy+PdTMda XejfTMOTeHI7002K+7LuknJ4gwqEHUxkMJaH29Xo= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726218AbfDEWdG (ORCPT ); Fri, 5 Apr 2019 18:33:06 -0400 Received: from mail.kernel.org ([198.145.29.99]:43956 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726124AbfDEWdG (ORCPT ); Fri, 5 Apr 2019 18:33:06 -0400 Received: from localhost (unknown [69.71.4.100]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 2A50E206BA; Fri, 5 Apr 2019 22:33:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1554503585; bh=7ewTkUrqrMaQHlGYWysY7oJ/SHY7xljwl2B1977CleM=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=Wfb9xaK30k1/3jfyuQBOTjYOhImWlvC5UntBiFIzFp5MzsyZ1fn8X89vb4D6zkIKI DXHZ3Ka+W3iEf9w+9saGyJOZKv0XIbRLeXKkyEg5koIrppqBaP7dpAGgZmM8TjRcXA 0d1+0P4smvLp2DSjMoGBVKjwDFqs8AlPHFEbuT6o= Date: Fri, 5 Apr 2019 17:33:00 -0500 From: Bjorn Helgaas To: Pierre =?iso-8859-1?Q?Cr=E9gut?= Cc: linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] PCI/IOV: update num_VFs earlier Message-ID: <20190405223300.GD159318@google.com> References: <20190329080058.21736-1-pierre.cregut@orange.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20190329080058.21736-1-pierre.cregut@orange.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-pci-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org On Fri, Mar 29, 2019 at 09:00:58AM +0100, Pierre Crégut wrote: > Ensure that iov->num_VFs is set before a netlink message is sent > when the number of VFs is changed. Only the path for num_VFs > 0 > is affected. The path for num_VFs = 0 is already correct. > > Monitoring programs can relie on netlink messages to track interface > change and query their state in /sys. But when sriov_numvfs is set to a > positive value, the netlink message is sent before the value is available > in sysfs. The value read after the message is received is always zero. Thanks, Pierre! Can you clue me in on where exactly the connection from sriov_enable() to netlink is? I see one side of the race is with sriov_numvfs_show(), but I don't know where the netlink message is sent. Is that connected with the kobject_uevent(KOBJ_CHANGE)? One thing this would help with is figuring out exactly how *much* earlier we need to set iov->num_VFs. It looks like the current patch sets it before we actually enable the VFs, so a user could read /sys/.../sriov_numvfs and get the wrong value. Of course, that's unavoidable; the question is whether it's OK to get the new value *before* it actually takes effect, or whether we want to return a stale value until after it takes effect. > Link: https://bugzilla.kernel.org/show_bug.cgi?id=202991 > Signed-off-by: Pierre Crégut > --- > note: the behaviour can be tested with the following shell script also > available on the bugzilla (d being the phy device name): > > ip monitor dev $d | grep --line-buffered "^[0-9]*:" | \ > while read line; do cat /sys/class/net/$d/device/sriov_numvfs; done > > drivers/pci/iov.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c > index 3aa115ed3a65..a9655c10e87f 100644 > --- a/drivers/pci/iov.c > +++ b/drivers/pci/iov.c > @@ -351,6 +351,7 @@ static int sriov_enable(struct pci_dev *dev, int nr_virtfn) > goto err_pcibios; > } > > + iov->num_VFs = nr_virtfn; > pci_iov_set_numvfs(dev, nr_virtfn); > iov->ctrl |= PCI_SRIOV_CTRL_VFE | PCI_SRIOV_CTRL_MSE; > pci_cfg_access_lock(dev); > @@ -363,7 +364,6 @@ static int sriov_enable(struct pci_dev *dev, int nr_virtfn) > goto err_pcibios; > > kobject_uevent(&dev->dev.kobj, KOBJ_CHANGE); > - iov->num_VFs = nr_virtfn; > > return 0; > > @@ -379,6 +379,7 @@ static int sriov_enable(struct pci_dev *dev, int nr_virtfn) > if (iov->link != dev->devfn) > sysfs_remove_link(&dev->dev.kobj, "dep_link"); > > + iov->num_VFs = 0; > pci_iov_set_numvfs(dev, 0); > return rc; > } > -- > 2.17.1 >