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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id C0F6AC02199 for ; Thu, 6 Feb 2025 18:20:41 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1tg6SL-0007YE-FY; Thu, 06 Feb 2025 13:18:29 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1tg6SJ-0007Xq-90 for qemu-devel@nongnu.org; Thu, 06 Feb 2025 13:18:27 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1tg6SH-0006Wp-IJ for qemu-devel@nongnu.org; Thu, 06 Feb 2025 13:18:27 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1738865903; h=from:from:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=kqhvfeo5m3+UNdRAo3LDzsdwGsCk3HFH0WEizYMVF8Y=; b=UrxiWMyFhoMWOpfUuYZQykTVuVq4KNaWT2EaSXY5k5qsmBLHsMHwKx1pNwWmpVrEmHgfCX Oj3NZuhRfSjtbbKFa7amNI2dJJPwwg04puuH175TKl7M8Q0v4mZw4fYgcUIIotGTLNuD0n zBbAm2RFCLHdKd7s2wvaIofBo7uqkgY= Received: from mx-prod-mc-05.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-480-fzQuamUoNfGYZsc9B0sb1A-1; Thu, 06 Feb 2025 13:18:21 -0500 X-MC-Unique: fzQuamUoNfGYZsc9B0sb1A-1 X-Mimecast-MFC-AGG-ID: fzQuamUoNfGYZsc9B0sb1A Received: from mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.17]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 2C9F719560A7; Thu, 6 Feb 2025 18:18:18 +0000 (UTC) Received: from redhat.com (unknown [10.42.28.33]) by mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id B1D891956051; Thu, 6 Feb 2025 18:18:12 +0000 (UTC) Date: Thu, 6 Feb 2025 18:18:09 +0000 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Jason Gunthorpe Cc: Shameerali Kolothum Thodi , "qemu-arm@nongnu.org" , "qemu-devel@nongnu.org" , "eric.auger@redhat.com" , "peter.maydell@linaro.org" , "nicolinc@nvidia.com" , "ddutile@redhat.com" , Linuxarm , "Wangzhou (B)" , jiangkunkun , Jonathan Cameron , "zhangfei.gao@linaro.org" , "nathanc@nvidia.com" Subject: Re: [RFC PATCH 0/5] hw/arm/virt: Add support for user-creatable nested SMMUv3 Message-ID: References: <47d2c2556d794d87abf440263b2f7cd8@huawei.com> <71116749d1234ab48a205fd2588151ec@huawei.com> <20250206170238.GG2960738@nvidia.com> <20250206174647.GA3480821@nvidia.com> <20250206175843.GI2960738@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20250206175843.GI2960738@nvidia.com> User-Agent: Mutt/2.2.13 (2024-03-09) X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 Received-SPF: pass client-ip=170.10.133.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Thu, Feb 06, 2025 at 01:58:43PM -0400, Jason Gunthorpe wrote: > On Thu, Feb 06, 2025 at 05:54:57PM +0000, Daniel P. Berrangé wrote: > > > > We shouldn't assume any VFIO device exists in the QEMU cnofig at the time > > > > we realize the virtual ssmu. I expect the SMMU may be cold plugged, while > > > > the VFIO devices may be hot plugged arbitrarly later, and we should have > > > > the association initialized the SMMU is realized. > > > > > > This is not supported kernel side, you can't instantiate a vIOMMU > > > without a VFIO device that uses it. For security. > > > > What are the security concerns here ? > > You should not be able to open iommufd and manipulate iommu HW that > you don't have a VFIO descriptor for, including creating physical > vIOMMU resources, allocating command queues and whatever else. > > Some kind of hot plug smmu would have to create a vSMMU without any > kernel backing and then later bind it to a kernel implementation. Ok, so if we give the info about the vSMMU <-> pSMMU binding to QEMU upfront, it can delay using it until the point where the kernel accepts it. This at least gives a clear design to applications outside QEMU, and hides the low level impl details to inside QEMU. With regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|