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=-3.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=no 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 A85D2C433DB for ; Mon, 8 Mar 2021 17:43:09 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 5F0CE652A6 for ; Mon, 8 Mar 2021 17:43:09 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5F0CE652A6 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linuxfoundation.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:42890 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1lJJuO-00029t-Fa for qemu-devel@archiver.kernel.org; Mon, 08 Mar 2021 12:43:08 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:51868) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lJJci-0004RS-5t for qemu-devel@nongnu.org; Mon, 08 Mar 2021 12:24:52 -0500 Received: from mail.kernel.org ([198.145.29.99]:47462) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lJJcf-0003SS-8o for qemu-devel@nongnu.org; Mon, 08 Mar 2021 12:24:51 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id A52356520F; Mon, 8 Mar 2021 17:24:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1615224287; bh=mM7ct2vgRlQeJ6mmmYx4ShAL1KKFFLg9U+ZCmnf0rDA=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=ox8FtV0m2DJVYbt3iY5k+JsCuBCZYeAax/5KG5HDdHKEeeI8sCl3nSGWG3yxIemTQ zo57Q6vcHbPtuQ3m++iZxB3o17ukYqBu+NyjDs2esBwc2yzujLL0srdvXbrkEFBJBk TuOz/byGz6rgCi4wOlsohTDSEYC+AgfW5dtmIhnk= Date: Mon, 8 Mar 2021 18:24:44 +0100 From: Greg KH To: Alexander Graf Subject: Re: [PATCH v8] drivers/misc: sysgenid: add system generation id driver Message-ID: References: <1615213083-29869-1-git-send-email-acatan@amazon.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Received-SPF: pass client-ip=198.145.29.99; envelope-from=gregkh@linuxfoundation.org; helo=mail.kernel.org X-Spam_score_int: -73 X-Spam_score: -7.4 X-Spam_bar: ------- X-Spam_report: (-7.4 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.251, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_HI=-5, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=unavailable autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Jason@zx2c4.com, areber@redhat.com, kvm@vger.kernel.org, linux-doc@vger.kernel.org, ghammer@redhat.com, vijaysun@ca.ibm.com, 0x7f454c46@gmail.com, qemu-devel@nongnu.org, mhocko@kernel.org, dgunigun@redhat.com, avagin@gmail.com, pavel@ucw.cz, ptikhomirov@virtuozzo.com, linux-s390@vger.kernel.org, corbet@lwn.net, mpe@ellerman.id.au, mst@redhat.com, ebiggers@kernel.org, borntraeger@de.ibm.com, sblbir@amazon.com, bonzini@gnu.org, arnd@arndb.de, jannh@google.com, raduweis@amazon.com, asmehra@redhat.com, Adrian Catangiu , rppt@kernel.org, luto@kernel.org, gil@azul.com, oridgar@gmail.com, colmmacc@amazon.com, tytso@mit.edu, ovzxemul@gmail.com, rdunlap@infradead.org, linux-kernel@vger.kernel.org, ebiederm@xmission.com, rafael@kernel.org, w@1wt.eu, dwmw@amazon.co.uk Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Mon, Mar 08, 2021 at 05:03:58PM +0100, Alexander Graf wrote: > > > On 08.03.21 15:36, Greg KH wrote: > > > > On Mon, Mar 08, 2021 at 04:18:03PM +0200, Adrian Catangiu wrote: > > > +static struct miscdevice sysgenid_misc = { > > > + .minor = MISC_DYNAMIC_MINOR, > > > + .name = "sysgenid", > > > + .fops = &fops, > > > +}; > > > > Much cleaner, but: > > > > > +static int __init sysgenid_init(void) > > > +{ > > > + int ret; > > > + > > > + sysgenid_data.map_buf = get_zeroed_page(GFP_KERNEL); > > > + if (!sysgenid_data.map_buf) > > > + return -ENOMEM; > > > + > > > + atomic_set(&sysgenid_data.generation_counter, 0); > > > + atomic_set(&sysgenid_data.outdated_watchers, 0); > > > + init_waitqueue_head(&sysgenid_data.read_waitq); > > > + init_waitqueue_head(&sysgenid_data.outdated_waitq); > > > + spin_lock_init(&sysgenid_data.lock); > > > + > > > + ret = misc_register(&sysgenid_misc); > > > + if (ret < 0) { > > > + pr_err("misc_register() failed for sysgenid\n"); > > > + goto err; > > > + } > > > + > > > + return 0; > > > + > > > +err: > > > + free_pages(sysgenid_data.map_buf, 0); > > > + sysgenid_data.map_buf = 0; > > > + > > > + return ret; > > > +} > > > + > > > +static void __exit sysgenid_exit(void) > > > +{ > > > + misc_deregister(&sysgenid_misc); > > > + free_pages(sysgenid_data.map_buf, 0); > > > + sysgenid_data.map_buf = 0; > > > +} > > > + > > > +module_init(sysgenid_init); > > > +module_exit(sysgenid_exit); > > > > So you do this for any bit of hardware that happens to be out there? > > Will that really work? You do not have any hwid to trigger off of to > > know that this is a valid device you can handle? > > The interface is already useful in a pure container context where the > generation change request is triggered by software. > > And yes, there are hardware triggers, but Michael was quite unhappy about > potential races between VMGenID change and SysGenID change and thus wanted > to ideally separate the interfaces. So we went ahead and isolated the > SysGenID one, as it's already useful as is. > > Hardware drivers to inject change events into SysGenID can then follow > later, for all different hardware platforms. But SysGenID as in this patch > is a completely hardware agnostic concept. Ok, so what is going to cause this driver to be automatically loaded? How will userspace "know" they want this and know to load it? This really is just a shared memory "driver", it's gotten so small now, so why can't this just be a userspace program/server now? :) thanks, greg k-h