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Shutemov" , "Hocko, Michal" , Muchun Song , John Hubbard Subject: Re: [PATCH v1 0/2] udmabuf: Add back support for mapping hugetlb pages Message-ID: References: <20230622072710.3707315-1-vivek.kasireddy@intel.com> <6e429fbc-e0e6-53c0-c545-2e2cbbe757de@redhat.com> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-ClientProxiedBy: CH0P221CA0046.NAMP221.PROD.OUTLOOK.COM (2603:10b6:610:11d::19) To LV2PR12MB5869.namprd12.prod.outlook.com (2603:10b6:408:176::16) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: LV2PR12MB5869:EE_|PH7PR12MB8014:EE_ X-MS-Office365-Filtering-Correlation-Id: e2390ab8-ce88-4a4d-55ad-08db740834ae X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:LV2PR12MB5869.namprd12.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230028)(4636009)(396003)(136003)(346002)(366004)(39860400002)(376002)(451199021)(478600001)(4744005)(2906002)(54906003)(38100700002)(2616005)(36756003)(5660300002)(966005)(6486002)(66946007)(66556008)(66476007)(6916009)(4326008)(316002)(41300700001)(8936002)(86362001)(7416002)(8676002)(6506007)(6512007)(107886003)(186003)(26005);DIR:OUT;SFP:1101; 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Also a resaonable thing to do > For instance, what if the userapp just punchs a hole in the shmem/hugetlbfs > file after creating the udmabuf (I see that F_SEAL_SHRINK is required, but > at least not F_SEAL_WRITE with current impl), and fault a new page into the > page cache? It becomes incoherent just like all other GUP users if userspace explicitly manipulates the VMAs. It is no different to what happens with VFIO, qemu should treat this memory the same as it does for VFIO memory. Jason