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 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id CD276C352A1 for ; Tue, 6 Dec 2022 16:55:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=W2Wu/VqSKp43h5x2rSzuMUJjgQaWCLtIuyJyNNcr5pk=; b=KgoW7mWqVWWM2D19dyhO5fv0ld RtTXU5EY8VvGOgjBX0gBM/9TreA0iew/zERDQ5XpldtyIkf0ziXVZVEbKjvEaykPEd+VOs9qV5UCW h3l0vQTEleDaOxFRQHzfJMUCaWXqZK4xc6FlenS5jt278mDk5qIfDAku6edjAn7/58wYnBSqOBE24 3ge0a5AuJ+19V/TkZOfoJaj4Cg0EzFujiQ0k7K3dPe7q4njTBOuOt6w3S8+dhzhQvg5u1fO2YAzVe YWjHjyk3M+gD1zcQEYTkcWRyuYOcn5oBTLh/+REvblvMMVuc5BnryJCaWqe07ZWmC7YtmHoCzFms6 vS57npHw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1p2bDx-00FUzd-Ox; Tue, 06 Dec 2022 16:55:17 +0000 Received: from verein.lst.de ([213.95.11.211]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1p2bDu-00FUoq-IG for linux-nvme@lists.infradead.org; Tue, 06 Dec 2022 16:55:16 +0000 Received: by verein.lst.de (Postfix, from userid 2407) id B56DF68B05; Tue, 6 Dec 2022 17:55:03 +0100 (CET) Date: Tue, 6 Dec 2022 17:55:03 +0100 From: Christoph Hellwig To: Jason Gunthorpe Cc: Christoph Hellwig , Lei Rao , kbusch@kernel.org, axboe@fb.com, kch@nvidia.com, sagi@grimberg.me, alex.williamson@redhat.com, cohuck@redhat.com, yishaih@nvidia.com, shameerali.kolothum.thodi@huawei.com, kevin.tian@intel.com, mjrosato@linux.ibm.com, linux-kernel@vger.kernel.org, linux-nvme@lists.infradead.org, kvm@vger.kernel.org, eddie.dong@intel.com, yadong.li@intel.com, yi.l.liu@intel.com, Konrad.wilk@oracle.com, stephen@eideticom.com, hang.yuan@intel.com Subject: Re: [RFC PATCH 1/5] nvme-pci: add function nvme_submit_vf_cmd to issue admin commands for VF driver. Message-ID: <20221206165503.GA8677@lst.de> References: <20221206055816.292304-1-lei.rao@intel.com> <20221206055816.292304-2-lei.rao@intel.com> <20221206061940.GA6595@lst.de> <20221206135810.GA27689@lst.de> <20221206153811.GB2266@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.17 (2007-11-01) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20221206_085514_768548_E2A74869 X-CRM114-Status: GOOD ( 13.45 ) X-BeenThere: linux-nvme@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "Linux-nvme" Errors-To: linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org On Tue, Dec 06, 2022 at 11:51:23AM -0400, Jason Gunthorpe wrote: > That is a big deviation from where VFIO is right now, the controlled > function is the one with the VFIO driver, it should be the one that > drives the migration uAPI components. Well, that is one way to see it, but I think the more natural way to deal with it is to drive everyting from the controlling function, because that is by definition much more in control. More importantly any sane design will have easy ways to list and manipulate all the controlled functions from the controlling functions, while getting from the controlled function to the controlling one is extremely awkward, as anything that can be used for that is by definition and information leak. It seems mlx5 just gets away with that by saying controlled functions are always VFs, and the controlling function is a PF, but that will break down very easily, especially once you want to nest the controlling scheme (and yes, I'm not making this up, as the nesting scheme is being proposed for nvme privately).