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X-OriginatorOrg: arm.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 03 Jun 2025 15:23:44.6140 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: a923ba6f-d53d-45fd-5ac3-08dda2b2a11a 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: DU2PEPF00028D0F.eurprd03.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: VE1PR08MB5741 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250603_082351_579509_3DF6255F X-CRM114-Status: GOOD ( 19.26 ) 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: , Cc: linux-arm-kernel@lists.infradead.org, ptosi@google.com, pcc@google.com, catalin.marinas@arm.com, bigeasy@linutronix.de, linux-kernel@vger.kernel.org, joey.gouly@arm.com, mcgrof@kernel.org, broonie@kernel.org, geert@linux-m68k.org, kristina.martsenko@arm.com, james.morse@arm.com, Will Deacon , rppt@kernel.org Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi Mark, > On Tue, Jun 03, 2025 at 12:14:18PM +0100, Yeoreum Yun wrote: > > > On Mon, Jun 02, 2025 at 06:50:53PM +0100, Yeoreum Yun wrote: > > > > So, what I think: > > > > 1. arm64_enter_el1_dbg() should ct_nmi_enter() as it is. > > > > 2. in bug_handler() while handling BUG_TYPE, add above ct_nmi_exit() > > > > conditional call. > > > > 3. DAIF.D and DAIF.A handling. > > > > > > No, that is not safe. In step 2, calling ct_nmi_exit() would undo *all* > > > of the ct_nmi_enter() logic, and may stop RCU from watching if the > > > exception was entered from some intermediate/inconsistent state. > > > > Yes if call ct_nmi_enter() without condition. > > But I imply with the condition check what I posted. > > if CT_NESTING_IRQ_NONIDLE, > > it wouldn't need call and that cpu can be watched by RCU. > > I am not keen on conditionally calling ct_nmi_exit(), and would strongly > prefer to avoid that, regardless of where that lives in the flow. > > I suspect that it would be bettter to triage the interrupted context > earlier, and rethink the way entry/exit works, but that's a much larger > bit of work and will take more thinking. Thanks for sharing your thought. I'll think about it and let me raise it again after ada's patchset is merged. -- Sincerely, Yeoreum Yun