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charset="us-ascii" Content-Transfer-Encoding: quoted-printable Precedence: bulk X-Mailing-List: virtualization@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-OriginatorOrg: marvell.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-AuthSource: DS0PR18MB5368.namprd18.prod.outlook.com X-MS-Exchange-CrossTenant-Network-Message-Id: 494611bf-40ba-47f6-3649-08dc595a9f48 X-MS-Exchange-CrossTenant-originalarrivaltime: 10 Apr 2024 12:34:53.3381 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 70e1fb47-1155-421d-87fc-2e58f638b6e0 X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: AqEvNRtVQtnWJCH0TqZKXgaDzLivgUJb1p4oRqPzJYDEndipIjrLmhCb69oMiNFrPVm8WgScEIGDFXd5Q9FO1w== X-MS-Exchange-Transport-CrossTenantHeadersStamped: CH3PR18MB5440 X-Proofpoint-GUID: oKbXQ7CJEFbxYAk2P7PL0XKiHLzz2v0Y X-Proofpoint-ORIG-GUID: oKbXQ7CJEFbxYAk2P7PL0XKiHLzz2v0Y X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.272,Aquarius:18.0.1011,Hydra:6.0.619,FMLib:17.11.176.26 definitions=2024-04-10_04,2024-04-09_01,2023-05-22_02 > Subject: Re: [EXTERNAL] Re: [PATCH] virtio: vdpa: vDPA driver for Marvell > OCTEON DPU devices >=20 > On Wed, Apr 10, 2024 at 10:15:37AM +0000, Srujana Challa wrote: > > > > > > + > > > > > > + domain =3D iommu_get_domain_for_dev(dev); > > > > > > + if (!domain || domain->type =3D=3D IOMMU_DOMAIN_IDENTIT= Y) { > > > > > > + dev_info(dev, "NO-IOMMU\n"); > > > > > > + octep_vdpa_ops.set_map =3D octep_vdpa_set_map; > > > > > > > > > > Is this a shortcut to have get better performance? DMA API > > > > > should have those greacefully I think. > > > > When IOMMU is disabled on host and set_map/dma_map is not set, > > > > vhost-vdpa is reporting an error "Failed to allocate domain, > > > > device is not > > > IOMMU cache coherent capable\n". > > > > Hence we are doing this way to get better performance. > > > > > > The problem is, assuming the device does not have any internal IOMMU. > > > > > > 1) If we allow it running without IOMMU, it opens a window for guest > > > to attack the host. > > > 2) If you see perforamnce issue with IOMMU_DOMAIN_IDENTITY, let's > > > report it to DMA/IOMMU maintiner to fix that > > It will be helpful for host networking case when iommu is disabled. > > Can we take the vfio pci driver approach as a reference where user > > explicitly set "enable_unsafe_noiommu_mode" using module param? >=20 > vfio is a userspace driver so it's userspace's responsibility. > what exactly ensures correctness here? does the device have an on-chip > iommu? > Our device features an on-chip IOMMU, although it is not utilized for host-= side targeted DMA operations. We included no-iommu mode in our driver to ensure that host applications, such as DPDK Virtio user PMD, continue to function = even when operating in a no-IOMMU mode. We observed performance impacts on certain low-end x86 machines when IOMMU mode was enabled. I think, correctness is Host userspace application's responsibility, in thi= s case when vhost-vdpa is used with Host application such as DPDK Virtio user PMD. =20 > > > > > > Thanks > > > > Thanks. > >