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charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: iommu-bounces@lists.linux-foundation.org Sender: "iommu" On Mon, Apr 04, 2022 at 01:43:49PM +0800, Lu Baolu wrote: > On 2022/3/30 19:58, Jason Gunthorpe wrote: > > > > Testing the group size is inherently the wrong test to make. > > > What is your suggestion then? > > Add a flag to the group that positively indicates the group can never > > have more than one member, even after hot plug. eg because it is > > impossible due to ACS, or lack of bridges, and so on. > > The check method seems to be bus specific. For platform devices, perhaps > this kind of information should be retrieved from firmware interfaces > like APCI or DT. > > From this point of view, would it be simpler and more reasonable for the > device driver to do such check? After all, it is the device driver that > decides whether to provide SVA services to the application via uacce. The check has to do with the interconnect, not the device - I don't see how a device driver would know any better. Why do you bring up uacce? Nothing should need uacce to access SVA. Jason _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 41031C433EF for ; Mon, 4 Apr 2022 21:27:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1380640AbiDDV1g (ORCPT ); Mon, 4 Apr 2022 17:27:36 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44246 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1379536AbiDDR0E (ORCPT ); Mon, 4 Apr 2022 13:26:04 -0400 Received: from NAM10-DM6-obe.outbound.protection.outlook.com (mail-dm6nam10on2067.outbound.protection.outlook.com [40.107.93.67]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 348DE30547 for ; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?53l09IMDJNrKYCOMRVJcPBsKv7cstjrPgsv1bgJqfrsVXc1ukfsYWmhbIDLo?= =?us-ascii?Q?UsePtRgcysPMKZYVCdgWmTDfctgvdUMtpHKX6wlAc12+qn3uriXHWZpJsLDI?= =?us-ascii?Q?uXw0NnEhNAK6/iHUWOrZg4z1HGJ+0r2demT0qCBxDSLvarDkzTKoOeyQzlXh?= =?us-ascii?Q?1Oge9cL6uRB/tN6LkszVMSiybUmHezGWsnQiKsRFT3VotvBH3I76U9kjMfp5?= =?us-ascii?Q?p8V3Kp/Pp6P4MCn4k3YImRSYi4BO0iK7PQQTC2jp1iG6Cl/dgPxkMYuYKYGu?= =?us-ascii?Q?tF6rgiSFy42k3BM1as+bhXpQM4WSJpqg7I6adpdCAEkcCfyCuJH4nZ8jjjxM?= =?us-ascii?Q?NHu2pLlHxWAfpDF6LwJLBy4O0Dbf5+9NMdgjs1vls0eKhfzuHOKNhmnnme80?= =?us-ascii?Q?gnSOUQK+I5AUnseU86KXciPytpw25KlqLu4pNgKubCEfZ7/GkLkgRqKYqiku?= =?us-ascii?Q?2yuRnvTGonnZJDZGMCiEyhhOkrd0WB4flKmYOHGVZYkIbortidXCcfSzyLKC?= =?us-ascii?Q?Akz5ezn+eivIPqdmvgHrbTPGg7Fxi9JTEvVcoDgfBnGXXHEEk31yrVSs9B2T?= =?us-ascii?Q?xMKc9bT/FsCbcWz9pBW8e9ljUwrTusouusAydTNBqsRcjym1XwoLW3E+u9q0?= =?us-ascii?Q?oPkwbayJw8Z9EyNZvlQSyIQJyCIEYBbec63BJl3TabAoKgxzJTMH6c8z2fI8?= =?us-ascii?Q?nde8E+n3cwN87ucbXMqQy48yMLiNKBUJ3qeD+RwsbZLsFypPux9BjRgl5UWw?= =?us-ascii?Q?B4C/Pscuk45gF4Ve0q8MjmyscnOuLll6i7ZTUZxfKd5TC7Cmt4/LCcJe/98x?= =?us-ascii?Q?/yQ4nZUnqauAXCefFQS2gxOhdeLqrdzYP3enIpCiK+xIv50lcJRaNXBVpCr9?= =?us-ascii?Q?8IsDeT/xlNwK9eMrilqWcZKwiga1V4oQnTGKvZ5RFBzKg7dBSoD/NEvbC7vI?= =?us-ascii?Q?5zvGkfQrEJGmtlHdtyAVJOtBmfUDvyjF10v2vWTbrlZ9YzINYnSyo1TKLWIo?= =?us-ascii?Q?T1NHuGeOemJ7/zR7XaEhhi4IYu4+Kp0xzyFzP/S4DJ6Ji6iYx9W1kBYJKXSd?= =?us-ascii?Q?An7Ju3Bju+vKfmfP9pBYVmQ/QsCG4+dn4EbMzvkN5PRuUuyOCG7JxokzxFKR?= =?us-ascii?Q?dk/VSZxCQbIo3iVTfW0U3hZdBBbwe93IzWv0/54BJEBPQtDZccmCAoCBedt0?= =?us-ascii?Q?54keLwAdD3LdlwONj4bH4kRBkOX9DjYI3lLMWNh+YuqoqhmnFX1tyW2BTk1L?= =?us-ascii?Q?61nuuoJJIdVfwzoZiOhGG8peKLJGxeOktublDUwe+lhOxo/Vf7rzlvAutFmM?= =?us-ascii?Q?dINOZ9WTvfcS3e9Z+tn9yZvUNRHJDcSw/IAlRgshkKt0CuKhceiagh0WsCtP?= =?us-ascii?Q?iaBCAO+Ug49G6mfTtuSULccp4KaGcECs7jRXR/R06cf9b5MRfgh0ip0CLvH9?= =?us-ascii?Q?Y/IiecR4GBQcEtFwSMKiEGfj2k+L8FgmmmIN7NYdbtfb1M6omSUu3+Ge8FW8?= =?us-ascii?Q?YuDT7D9XEzdsRT9DPuTMmVF4YzOW4+tzKH+QBDLoBwI8Z2OMDitTbmon6+5r?= =?us-ascii?Q?QuyGc7UBsT7jv9s7Mm3TcugzF7/Zi9glK+rbp6mjGZigTSn0AqbXJ1debWG0?= =?us-ascii?Q?if9ydsfOjCJ5etFVlWHWaX6h9zWXhM4rhMpI/sUPktEshrE7iLgIlxk8s7ZO?= =?us-ascii?Q?im0EtAyY9IADPGbSrrQsxeu5tZ0BeFQeDS1K+y5TGgrx3Qm6szNqXaK9GD0c?= =?us-ascii?Q?dr2g7eo0eQ=3D=3D?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: 0ee14c9e-1125-4801-ba5c-08da165feb21 X-MS-Exchange-CrossTenant-AuthSource: MN2PR12MB4192.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 04 Apr 2022 17:24:05.1887 (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: j92MkwaDdg+lmpjb+K2vBVYtoPL2xFApK++y9uGcMyZQbgk09+n7lFdGNbgZ7Aza X-MS-Exchange-Transport-CrossTenantHeadersStamped: BN6PR1201MB0066 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Apr 04, 2022 at 01:43:49PM +0800, Lu Baolu wrote: > On 2022/3/30 19:58, Jason Gunthorpe wrote: > > > > Testing the group size is inherently the wrong test to make. > > > What is your suggestion then? > > Add a flag to the group that positively indicates the group can never > > have more than one member, even after hot plug. eg because it is > > impossible due to ACS, or lack of bridges, and so on. > > The check method seems to be bus specific. For platform devices, perhaps > this kind of information should be retrieved from firmware interfaces > like APCI or DT. > > From this point of view, would it be simpler and more reasonable for the > device driver to do such check? After all, it is the device driver that > decides whether to provide SVA services to the application via uacce. The check has to do with the interconnect, not the device - I don't see how a device driver would know any better. Why do you bring up uacce? Nothing should need uacce to access SVA. Jason