Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::3:6 as permitted sender) client-ip=2620:137:e000::3:6;
Received-SPF: Pass (protection.outlook.com: domain of nvidia.com designates
 216.228.117.160 as permitted sender) receiver=protection.outlook.com;
 client-ip=216.228.117.160; helo=mail.nvidia.com; pr=C
Date:   Mon, 11 Dec 2023 12:11:25 -0800
From:   Nicolin Chen <nicolinc@nvidia.com>
To:     Jason Gunthorpe <jgg@nvidia.com>
CC:     Yi Liu <yi.l.liu@intel.com>,
        "Giani, Dhaval" <Dhaval.Giani@amd.com>,
        Vasant Hegde <vasant.hegde@amd.com>,
        Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>,
        <joro@8bytes.org>, <alex.williamson@redhat.com>,
        <kevin.tian@intel.com>, <robin.murphy@arm.com>,
        <baolu.lu@linux.intel.com>, <cohuck@redhat.com>,
        <eric.auger@redhat.com>, <kvm@vger.kernel.org>,
        <mjrosato@linux.ibm.com>, <chao.p.peng@linux.intel.com>,
        <yi.y.sun@linux.intel.com>, <peterx@redhat.com>,
        <jasowang@redhat.com>, <shameerali.kolothum.thodi@huawei.com>,
        <lulu@redhat.com>, <iommu@lists.linux.dev>,
        <linux-kernel@vger.kernel.org>, <linux-kselftest@vger.kernel.org>,
        <zhenzhong.duan@intel.com>, <joao.m.martins@oracle.com>,
        <xin.zeng@intel.com>, <yan.y.zhao@intel.com>
Subject: Re: [PATCH v6 0/6] iommufd: Add nesting infrastructure (part 2/2)
Message-ID: <ZXds7V0Dz0ycF5IR@Asurada-Nvidia>
References: <20231117130717.19875-1-yi.l.liu@intel.com>
 <20231209014726.GA2945299@nvidia.com>
 <77ac47d0-2ef0-41fa-86c2-091358541465@intel.com>
 <20231211132041.GE2944114@nvidia.com>
MIME-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-Disposition: inline
In-Reply-To: <20231211132041.GE2944114@nvidia.com>
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 11 Dec 2023 20:11:44.0882
 (UTC)
X-MS-Exchange-CrossTenant-Network-Message-Id: 348ab46a-cbd1-4c1f-f1bb-08dbfa85656c
X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a
X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[216.228.117.160];Helo=[mail.nvidia.com]
X-MS-Exchange-CrossTenant-AuthSource: DS3PEPF000099DC.namprd04.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Anonymous
X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem
X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM8PR12MB5399
X-Spam-Status: No, score=-0.9 required=5.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED,
	DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,
	MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,T_SCC_BODY_TEXT_LINE
	autolearn=unavailable autolearn_force=no version=3.4.6
X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on pete.vger.email
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org
X-Greylist: Sender passed SPF test, not delayed by milter-greylist-4.6.4 (pete.vger.email [0.0.0.0]); Mon, 11 Dec 2023 12:11:57 -0800 (PST)

On Mon, Dec 11, 2023 at 09:20:41AM -0400, Jason Gunthorpe wrote:
> On Mon, Dec 11, 2023 at 08:35:09PM +0800, Yi Liu wrote:
> > > So.. In short.. Invalidation is a PITA. The idea is the same but
> > > annoying little details interfere with actually having a compltely
> > > common API here. IMHO the uAPI in this series is fine. It will support
> > > Intel invalidation and non-ATC invalidation on AMD/ARM. It should be
> > > setup to allow that the target domain object can be any HWPT.
> > 
> > This HWPT is still nested domain. Is it? But it can represent a guest I/O
> > page table (VT-d), guest CD table (ARM), guest CR3 Table (AMD, it seems to
> > be a set of guest CR3 table pointers). May ARM and AMD guys keep me honest
> > here.
> 
> I was thinking ARM would not want to use a nested domain because
> really the invalidation is global to the entire nesting parent.
> 
> But, there is an issue with that - the nesting parent could be
> attached to multiple iommu instances but we only want to invalidate a
> single instance. 

I am still not sure about attaching an S2 domain to multiple
SMMUs. An S2 domain is created per SMMU, and we have such a
rejection in arm_smmu_attach_dev():
	} else if (smmu_domain->smmu != smmu)
		ret = -EINVAL;

I understand that it would be probably ideal to share the S2
iopt among the SMMUs. But in the driver the objects (domain)
holding a shared S2 iopt must be different to allocate their
own VMIDs, right?

Thanks
Nicolin