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X-OriginatorOrg: arm.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 17 Apr 2023 07:46:36.2769 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 44667e34-dc54-4fcf-b954-08db3f17df1a X-MS-Exchange-CrossTenant-Id: f34e5979-57d9-4aaa-ad4d-b122a662184d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=f34e5979-57d9-4aaa-ad4d-b122a662184d;Ip=[63.35.35.123];Helo=[64aa7808-outbound-1.mta.getcheckrecipient.com] X-MS-Exchange-CrossTenant-AuthSource: DBAEUR03FT017.eop-EUR03.prod.protection.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: PA4PR08MB6207 > On 16 Apr 2023, at 15:32, Julien Grall wrote: >=20 > From: Julien Grall >=20 > In follow-up patches we will need to have part of Xen identity mapped in > order to safely switch the TTBR. >=20 > On some platform, the identity mapping may have to start at 0. If we alwa= ys > keep the identity region mapped, NULL pointer dereference would lead to > access to valid mapping. >=20 > It would be possible to relocate Xen to avoid clashing with address 0. > However the identity mapping is only meant to be used in very limited > places. Therefore it would be better to keep the identity region invalid > for most of the time. >=20 > Two new external helpers are introduced: > - arch_setup_page_tables() will setup the page-tables so it is > easy to create the mapping afterwards. > - update_identity_mapping() will create/remove the identity mapping >=20 > Signed-off-by: Julien Grall >=20 Hi Julien, Reviewed-by: Luca Fancellu