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charset="us-ascii" Content-ID: <3FABDF726EC98D4A8686934A91D5C61A@namprd05.prod.outlook.com> Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginatorOrg: vmware.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-AuthSource: BY3PR05MB8531.namprd05.prod.outlook.com X-MS-Exchange-CrossTenant-Network-Message-Id: 0c1337da-af4d-4de8-b01f-08daa24a19a5 X-MS-Exchange-CrossTenant-originalarrivaltime: 29 Sep 2022 18:40:36.7446 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: b39138ca-3cee-4b4a-a4d6-cd83d9dd62f0 X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: 6BU956YFgRa1QlnQ7xT3Lxxplvf9sNfwGizsr9zM9P0RUli9a9xa/Fv8rkyfY7l2IdCxBFG4SnGlWu2534czWA== X-MS-Exchange-Transport-CrossTenantHeadersStamped: BYAPR05MB4582 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sep 29, 2022, at 11:29 AM, Chih-En Lin wrote: > That case could be caught in copy_pte_range(): in case we'd have to alloc= ate >> a page via page_copy_prealloc(), we'd have to fall back to the ordinary >> "separate page table for the child" way of doing things. >>=20 >> But that looks doable to me. >=20 > Sounds good. :) Chih-En, I admit I did not fully read the entire correspondence and got dee= p into all the details. I would note, however, that there are several additional components that I did not see (and perhaps missed) in your patches. Basically, there are many page-table manipulations that are done not through the page-fault handler o= r reclamation mechanisms. I did not see any of them being addressed. So if/when you send a new version, please have a look at mprotect(), madvise(), soft-dirty, userfaultfd and THP. In these cases, I presume, you would have to COW-break (aka COW-unshare) the page-tables.