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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?rgkMwjRb2JXM3MTBT8AYolQ9cNZInC13JXaaImymWVTIfirIj0mbheaR1RSA?= =?us-ascii?Q?oSFr39XqbSF/2R/MgL+FnAZdFLAIrYfCLgIzBbCTjLQf7xiB48DsW9iQRL8m?= =?us-ascii?Q?GM1umxzA+eybrajnQKSIt12q5EX0WfznXem6tOkhD5gJ+4nawOlfdyP17j77?= =?us-ascii?Q?vYZ9/BAq+u7w8l8i/Ju0V0RUhLGgx1hDz3M6npXGWUPJQjSbHEippgRW5qDy?= =?us-ascii?Q?hPN806qE1uBBKNqDZVx+xhVHlKH4adlkUzux3zqOtJNTs77po5CiIcUxc8n9?= =?us-ascii?Q?G4SHdycySkW12iABnOf+kckw5qK6RoK7PjNd7z0SnlKGUK3zxcwdidiDmSvl?= =?us-ascii?Q?u9b5dwIfURmXMB5+lYe8+x/YNwE7luGGZJpF/sJM17Zi17/NA7WphcAiwKvB?= =?us-ascii?Q?r5LOB2iZV2ruyf0Co1lRSZXpGxeBJ2tJU4c9HuDo4RSatwx+7PLVLeRXas7D?= =?us-ascii?Q?oVu+II4HfBiXNR4BpBQ4pgeVMkmnTa+C03w6vYg7xRjoV2R56M0ZqNJVWzUd?= =?us-ascii?Q?fKKe2oz+pu/Xuh6mwrn6fd16VxeDPW5qwbaJBnLHSXOarK5DSahTZG+l5xro?= =?us-ascii?Q?CYzwhp0bcdKIzJmh+d5oc8h6aK/qQvr24Nv0DOIwnTzQd1Fcz39E+wKs2whM?= =?us-ascii?Q?+laBlf6gPHamBDu7KsaHUHSA+G8HWgjJFdmR4Yl60xqTu1jlwDlHecBHEyH0?= =?us-ascii?Q?do0FsAqh3HPNntmc+w1fhPghYhq3pUQSFpcJv401ANiZgsQzsX/8nim8F4Zh?= =?us-ascii?Q?kYcKtvm450HqP/AqNCsqESN+1kvM9x61SZkD8chprfltYGpJlC/bFT5OV7L5?= =?us-ascii?Q?EKJ/y6gIBp216Yw4/TbT8nocvPJfK/lYrFUcpQOoGM558tHc0Cc7SaMisQt+?= =?us-ascii?Q?Za0Nrj7nI22ni5ydZdV+HuhEu2esO/0gkuSDqfbKqm9EiWP9Q0tvAnHx9JLN?= =?us-ascii?Q?B3mtg77I8+HAfaSbef8mF3RYS+0fGSzPUJ+XSDw9HGKnDHHyAwaVpGLgxSJ3?= =?us-ascii?Q?Mf/QSJsXOxkvlwfeiIt0jB7pA8t79lSG6DAxQr+ahZzAaoOfesbgioUlmFRn?= =?us-ascii?Q?UxSZCzloVhBp7IFtqRbHWa8eaNDFpSLqBXiE17XnYCeKgF8wtKjb8BRnjo47?= =?us-ascii?Q?U+o98zmt/5LaA5y0GPvoLmX+08FT9Ykm5ByyN5qWdo5m1niz8s2fPBMhfHQZ?= =?us-ascii?Q?5YFDRWyapiG95950KdH7jCJaZ2mfmilcJTfvTLKjzdf13Eyi78NvcUkBdcL0?= =?us-ascii?Q?VO18eGA8ftCyz6lo8Ge2fLwMaFJqBWg7nJGYP2pfRvma1OGtldYUSJXY+wOQ?= =?us-ascii?Q?THtOm2MrXr8FhsSLAogu9hFhnF3UZGEogMnJZwnYm9qx3yYrMw01Fn6H36H6?= =?us-ascii?Q?AulkRWrMoxJzE0KMt21WH3faUlag2KU4YrOaGUG6oYV5UvhNHx6ZQaYpnJeg?= =?us-ascii?Q?3vigzV8bXguczPjZWs1x2F+mzymgk3vHkBqFTvx/JExio3YNF78LDcHNmwwT?= =?us-ascii?Q?ZHy2b0TukIuVw9nNeMlpQoRUp6dqYjUftQ/z8RCKROZ0sKRmKXuV39IYuroc?= =?us-ascii?Q?eihXG3H4LL/x9OCLWoqDW/nWv5VSuu+CTrhnole3?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: c77b44c3-9dfe-44a7-7584-08dafa5059cf X-MS-Exchange-CrossTenant-AuthSource: LV2PR12MB5869.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 19 Jan 2023 19:07:03.9473 (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: 926Gsi+zObgoZs63b9t0dAwcqiao95LzrlfHgUpAZWK9E/1hU9ezVEJhlob0sVnw X-MS-Exchange-Transport-CrossTenantHeadersStamped: SN7PR12MB7273 Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Tue, Jan 17, 2023 at 05:49:34AM -0800, Yi Liu wrote: > This is to avoid a circular refcount problem between the kvm struct and > the device file. KVM modules holds device/group file reference when the > device/group is added and releases it per removal or the last kvm reference > is released. This reference model is ok for the group since there is no > kvm reference in the group paths. > > But it is a problem for device file since the vfio devices may get kvm > reference in the device open path and put it in the device file release. > e.g. Intel kvmgt. This would result in a circular issue since the kvm > side won't put the device file reference if kvm reference is not 0, while > the vfio device side needs to put kvm reference in the release callback. > > To solve this problem for device file, let vfio provide release() which > would be called once kvm file is closed, it won't depend on the last kvm > reference. Hence avoid circular refcount problem. > > Suggested-by: Kevin Tian > Signed-off-by: Yi Liu > --- > virt/kvm/vfio.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) Reviewed-by: Jason Gunthorpe >From Alex's remarks please revise the commit message and add a Fixes line of some kind that this solves the deadlock Matthew was working on, and send it stand alone right away Jason