From mboxrd@z Thu Jan 1 00:00:00 1970 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.subspace.kernel.org (Postfix) with ESMTPS id 31E0D12C52F; Tue, 9 Jul 2024 06:09:42 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.137.202.133 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1720505383; cv=none; b=jQHj1H1NgDnjY1KZu0w6tLekzUSAEUiRQ4P2H9HmLsh0gHmRfFresdjBkYBr8EEjTITIjAnZ4R1bykvaplN4+wCjeQuCfVdeia6yUGvAstAQWWXZjDLyZzX/ouTuMOAesaiwqLvkUnv+bHuFOVtsrQ9GXUUc83L62ckBI7zy9So= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1720505383; c=relaxed/simple; bh=FO/e6sfjH8/QAUa41deJXp8jfrL365o1V/w4bikvz/s=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=LTyEwcGa6r8H3VtIbnXZEjr9q4lxklc8lY4rq1NNoUYntZXobHdUCbAmBZEHo8wIWy86XxVY1ST7cHK9pXZwYkIRQRgGKBJYxYePr1nRO//geAyUyMac5G0ReNAF/J9+2Oq9Zyq9+yos6p6fEesxHKBhtxq1aCSaUdE+KNFnyVo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=bombadil.srs.infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=aWeNn4Sv; arc=none smtp.client-ip=198.137.202.133 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=bombadil.srs.infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="aWeNn4Sv" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20210309; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=sl47jH5hsCNX2lI/FbDxlZ/pLUml99/KsZPpS5ibLgA=; b=aWeNn4SvV3oPmk3OO0U3RCNuQy KdKA+6lBgs/YY6hKVbZdnWawkd1n2WLes9tJL2ZJd8AniZgEo7tt3Yjto211xN9H8UXAGMayeGBf9 lW+PHVRBlw9Vxt01G90QqxpmJWklB4cG9lN7SDubWUy1YG9nvVit/jhyNHANCjzSEeRoHmS0maV5Y OpGrBlD2uxYX9QmRqem8PNPruAUFMFEghYPjI/uJPVJn1vwibSPkbvZYdmwhXt1w/SJD4zEa+Vb5H kmxfOJ0xajHBfnzJSG50nMakl/FGRP/jAV5MbgpTyUoUpalj0KGXoahx08mcqtaMqWcSFmZDd40wF 6aCD+o5w==; Received: from hch by bombadil.infradead.org with local (Exim 4.97.1 #2 (Red Hat Linux)) id 1sR42n-000000061O2-2QHu; Tue, 09 Jul 2024 06:09:41 +0000 Date: Mon, 8 Jul 2024 23:09:41 -0700 From: Christoph Hellwig To: Dan Williams Cc: ksummit@lists.linux.dev, linux-cxl@vger.kernel.org, linux-rdma@vger.kernel.org, netdev@vger.kernel.org, jgg@nvidia.com Subject: Re: [MAINTAINERS SUMMIT] Device Passthrough Considered Harmful? Message-ID: References: <668c67a324609_ed99294c0@dwillia2-xfh.jf.intel.com.notmuch> Precedence: bulk X-Mailing-List: ksummit@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <668c67a324609_ed99294c0@dwillia2-xfh.jf.intel.com.notmuch> X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html Passthrough in general is useful, but the problem is that protocols aren't designed with it in mind. Look at the list of command that affect too much state and we have to block in SCSI and NVMe. And in NVMe I'm fighting a constant fight in the technical working group to not add new command that instantly disable the access control we've built into NVMe passthrough. So IMHO passthrough can be good idea, but only if the protocol is designed for it, and protocol designer generally have a hard time how software works at all, never mind the futuristic concepts of layering, abstraction and access control.