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Tsirkin" CC: "virtio-dev@lists.oasis-open.org" , "cohuck@redhat.com" , "virtio-comment@lists.oasis-open.org" , Shahaf Shuler Thread-Topic: [PATCH 00/11] Introduce transitional mmr pci device Thread-Index: AQHZY1tF5ObSeHDFk0eWHj0gIzL7fK8UdveAgAD15oCABER6gIAAAE0w Date: Mon, 3 Apr 2023 14:57:26 +0000 Message-ID: References: <20230330225834.506969-1-parav@nvidia.com> <20230331024500-mutt-send-email-mst@kernel.org> <0dcd9907-4bb0-ef0d-678d-5bc8f0ded9ec@nvidia.com> <20230403105050-mutt-send-email-mst@kernel.org> In-Reply-To: <20230403105050-mutt-send-email-mst@kernel.org> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: authentication-results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=nvidia.com; x-ms-publictraffictype: Email x-ms-traffictypediagnostic: PH0PR12MB5481:EE_|LV2PR12MB5751:EE_ x-ms-office365-filtering-correlation-id: 483e1ddb-bad8-45af-5f96-08db3453bd15 x-ms-exchange-senderadcheck: 1 x-ms-exchange-antispam-relay: 0 x-microsoft-antispam: BCL:0; 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charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-AuthSource: PH0PR12MB5481.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-Network-Message-Id: 483e1ddb-bad8-45af-5f96-08db3453bd15 X-MS-Exchange-CrossTenant-originalarrivaltime: 03 Apr 2023 14:57:26.2182 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: dM/mWI2osq59xj60gK4F8TF88ujf55LeXHXnmtOPtdsloTMAc7i64iJw6Yz5XwHp8VvPU8PmV5/gyPTzwXAUpg== X-MS-Exchange-Transport-CrossTenantHeadersStamped: LV2PR12MB5751 Subject: [virtio-comment] RE: [PATCH 00/11] Introduce transitional mmr pci device > From: Michael S. Tsirkin > Sent: Monday, April 3, 2023 10:53 AM >=20 > On Fri, Mar 31, 2023 at 05:43:11PM -0400, Parav Pandit wrote: > > > I can not say I thought about this > > > deeply so maybe there's some problem, or maybe it's a worse approach > > > - could you comment on this? It looks like this could be a smaller > > > change, but maybe it isn't? Did you consider this option? > > > > We can possibly let both the options open for device vendors to impleme= nt. > > > > Change wise transport VQ is fairly big addition for both hypervisor > > driver and also for the device. >=20 > OTOH it is presumably required for scalability anyway, no? No. Most new generation SIOV and SR-IOV devices operate without any para-virtua= lization. > And presumably it can all be done in firmware ... > Is there actual hardware that can't implement transport vq but is going t= o > implement the mmr spec? >=20 Nvidia and Marvell DPUs implement MMR spec. Transport VQ has very high latency and DMA overheads for 2 to 4 bytes read/= write. And before discussing "why not that approach", lets finish reviewing "this = approach" first. This publicly archived list offers a means to provide input to the=0D OASIS Virtual I/O Device (VIRTIO) TC.=0D =0D In order to verify user consent to the Feedback License terms and=0D to minimize spam in the list archive, subscription is required=0D before posting.=0D =0D Subscribe: virtio-comment-subscribe@lists.oasis-open.org=0D Unsubscribe: virtio-comment-unsubscribe@lists.oasis-open.org=0D List help: virtio-comment-help@lists.oasis-open.org=0D List archive: https://lists.oasis-open.org/archives/virtio-comment/=0D Feedback License: https://www.oasis-open.org/who/ipr/feedback_license.pdf=0D List Guidelines: https://www.oasis-open.org/policies-guidelines/mailing-lists=0D Committee: https://www.oasis-open.org/committees/virtio/=0D Join OASIS: https://www.oasis-open.org/join/