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=-6.7 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 855A3C3A5A3 for ; Tue, 27 Aug 2019 15:39:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 66E4C2184D for ; Tue, 27 Aug 2019 15:39:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727306AbfH0Pjn (ORCPT ); Tue, 27 Aug 2019 11:39:43 -0400 Received: from mx1.redhat.com ([209.132.183.28]:19773 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726190AbfH0Pjn (ORCPT ); Tue, 27 Aug 2019 11:39:43 -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 0EB2418C890F; Tue, 27 Aug 2019 15:39:43 +0000 (UTC) Received: from gondolin (dhcp-192-222.str.redhat.com [10.33.192.222]) by smtp.corp.redhat.com (Postfix) with ESMTP id 947C95D6B0; Tue, 27 Aug 2019 15:39:39 +0000 (UTC) Date: Tue, 27 Aug 2019 17:39:37 +0200 From: Cornelia Huck To: Alex Williamson Cc: Parav Pandit , Jiri Pirko , "kwankhede@nvidia.com" , "davem@davemloft.net" , "kvm@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "netdev@vger.kernel.org" Subject: Re: [PATCH 2/4] mdev: Make mdev alias unique among all mdevs Message-ID: <20190827173937.3e39f578.cohuck@redhat.com> In-Reply-To: <20190827092855.29702347@x1.home> References: <20190826204119.54386-1-parav@mellanox.com> <20190826204119.54386-3-parav@mellanox.com> <20190827122928.752e763b.cohuck@redhat.com> <20190827132946.0b92d259.cohuck@redhat.com> <20190827092855.29702347@x1.home> Organization: Red Hat GmbH 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-4.6.2 (mx1.redhat.com [10.5.110.70]); Tue, 27 Aug 2019 15:39:43 +0000 (UTC) Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Tue, 27 Aug 2019 09:28:55 -0600 Alex Williamson wrote: > On Tue, 27 Aug 2019 13:29:46 +0200 > Cornelia Huck wrote: > > > On Tue, 27 Aug 2019 11:08:59 +0000 > > Parav Pandit wrote: > > > > > > -----Original Message----- > > > > From: Cornelia Huck > > > > Sent: Tuesday, August 27, 2019 3:59 PM > > > > To: Parav Pandit > > > > Cc: alex.williamson@redhat.com; Jiri Pirko ; > > > > kwankhede@nvidia.com; davem@davemloft.net; kvm@vger.kernel.org; linux- > > > > kernel@vger.kernel.org; netdev@vger.kernel.org > > > > Subject: Re: [PATCH 2/4] mdev: Make mdev alias unique among all mdevs > > > > > > > > On Mon, 26 Aug 2019 15:41:17 -0500 > > > > Parav Pandit wrote: > > > > > > > > > Mdev alias should be unique among all the mdevs, so that when such > > > > > alias is used by the mdev users to derive other objects, there is no > > > > > collision in a given system. > > > > > > > > > > Signed-off-by: Parav Pandit > > > > > --- > > > > > drivers/vfio/mdev/mdev_core.c | 5 +++++ > > > > > 1 file changed, 5 insertions(+) > > > > > > > > > > diff --git a/drivers/vfio/mdev/mdev_core.c > > > > > b/drivers/vfio/mdev/mdev_core.c index e825ff38b037..6eb37f0c6369 > > > > > 100644 > > > > > --- a/drivers/vfio/mdev/mdev_core.c > > > > > +++ b/drivers/vfio/mdev/mdev_core.c > > > > > @@ -375,6 +375,11 @@ int mdev_device_create(struct kobject *kobj, struct > > > > device *dev, > > > > > ret = -EEXIST; > > > > > goto mdev_fail; > > > > > } > > > > > + if (tmp->alias && strcmp(tmp->alias, alias) == 0) { > > > > > > > > Any way we can relay to the caller that the uuid was fine, but that we had a > > > > hash collision? Duplicate uuids are much more obvious than a collision here. > > > > > > > How do you want to relay this rare event? > > > Netlink interface has way to return the error message back, but sysfs is limited due to its error code based interface. > > > > I don't know, that's why I asked :) > > > > The problem is that "uuid already used" and "hash collision" are > > indistinguishable. While "use a different uuid" will probably work in > > both cases, "increase alias length" might be a good alternative in some > > cases. > > > > But if there is no good way to relay the problem, we can live with it. > > It's a rare event, maybe just dev_dbg(dev, "Hash collision creating alias \"%s\" for mdev device %pUl\n",... Sounds good to me.