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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: SNZaPnFZ038QchoHBY80dcROTRj4bTztFIs10cD0gOY1u1/+JAFaxZ4JxCIbXf7mETNxtmeFO8RXljdGIrn+qqK1aO1Y/yc/6hsX+cVG9Z89vOuaSCmNKGW4tqSjHgkCLHibJ81CNPT72NbPwvJDJBjCSNdzyVp8QWv8qJWzHgeapRWkIkjpzeBoywCnxktARhMuRFwp4iP3ZyjcOaJXWNI0otXqkA9JZwyuZTQKihG5YZnf6jgwilk+OUKKmKo0DxseTX/9fYk1/Ws/hHK7TJBj1mUG1BbE3kTrOfAO1N1iSdb10ZkUMIV6Df7tub70klo8EVap3WER9Shrd9XhDCV/fZFwL5GSfYLaWxO/f7n15mx5ZgONAhxZxOmgPdzwVgUN58hIIHQojm2SBelwdA4dxW636d4ilyV43eJ29O4sRvsRTeNqd1HuKDNBfO7I X-OriginatorOrg: arm.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 13 Mar 2026 10:00:54.0712 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: c527f024-e1cb-47b2-be78-08de80e76a41 X-MS-Exchange-CrossTenant-Id: f34e5979-57d9-4aaa-ad4d-b122a662184d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=f34e5979-57d9-4aaa-ad4d-b122a662184d;Ip=[4.158.2.129];Helo=[outbound-uk1.az.dlp.m.darktrace.com] X-MS-Exchange-CrossTenant-AuthSource: DU2PEPF00028D08.eurprd03.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: DU0PR08MB8229 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260313_030059_041937_988A8512 X-CRM114-Status: GOOD ( 13.30 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi Catalin, > On Fri, Feb 27, 2026 at 03:17:04PM +0000, Yeoreum Yun wrote: > > +static int __lsui_swap_desc(u64 __user *ptep, u64 old, u64 new) > > +{ > > + u64 tmp = old; > > + int ret = 0; > > + > > + /* > > + * FEAT_LSUI is supported since Armv9.6, where FEAT_PAN is mandatory. > > + * However, this assumption may not always hold: > > + * > > + * - Some CPUs advertise FEAT_LSUI but lack FEAT_PAN. > > + * - Virtualisation or ID register overrides may expose invalid > > + * feature combinations. > > + * > > + * Rather than disabling FEAT_LSUI when FEAT_PAN is absent, wrap LSUI > > + * instructions with uaccess_ttbr0_enable()/disable() when > > + * ARM64_SW_TTBR0_PAN is enabled. > > + */ > > + uaccess_ttbr0_enable(); > > + > > + asm volatile(__LSUI_PREAMBLE > > I haven't tried, so just asking. Does the toolchain complain if it does > not support LSUI or is this path eliminated (due to > cpucap_is_possible()) before being handed over to gas? It's probably > fine but worth checking. Yes I did with clang-19 and that's one of v14's modification: - https://lore.kernel.org/all/20260225182708.3225211-1-yeoreum.yun@arm.com/ -- Sincerely, Yeoreum Yun