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X-OriginatorOrg: arm.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 18 Aug 2025 15:19:19.9675 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 6edb02f2-bf67-448b-57aa-08ddde6a9ac6 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: DB1PEPF000509EE.eurprd03.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: AS8PR08MB10172 Hi Andery, > On Mon, Aug 18, 2025 at 3:11 PM Yeoreum Yun wrote: > > > > > > + hw_enable_tag_checks_write_only()) { > > > > + kasan_arg_write_only == KASAN_ARG_WRITE_ONLY_OFF; > > > > > > Typo in == in the line above. But also I think we can just drop the > > > line: kasan_arg_write_only is KASAN_ARG_WRITE_ONLY_ON after all, it's > > > just not supported and thus kasan_flag_write_only is set to false to > > > reflect that. > > > > Sorry :\ I've missed this fix from patch 3... this should be == to =. > > > > However, we couldn't remove kasan_arg_write_only check in condition. > > If one of cpu get failed to hw_enable_tag_checks_write_only() then > > By changing this with KASAN_ARG_WRITE_ONLY_OFF, It prevent to call > > hw_eanble_tag_checks_write_only() in other cpu. > > Is it possible that the write-only mode will fail to be enabled on one > CPU but then get enabled successfully for another? > > What would happen with the current code if the first CPU succeeds in > enabling the write-only mode, and the second one fails? The only failure case is when CPU doesn't support the MTE_STORE_ONLY feature. Since MTE_STORE_ONLY is BOOT CPU feature, the CPUs have two state -- all CPUs have a MTE_STORE_ONLY feature or they doesn't have it. So when boot-cpu try to enable the write-only option according to "write_only=on" boot argument but the cpu doesn't have this feature, hw_enable_tag_checks_write_only() will fail and prevent the calling hw_enable_tag_checks_write_only() in other cpu by kasan_arg_write_only as OFF to prevent other cpu call this function since it'll be failed anyway. So there is no case for failure -- the first CPU succeeds but second one fails. if first one succeeds, all cpus will success ans vice versa. This condition just to prevent to call hw_enable_tags_checks_write_only() by other cpu if first cpu found it doesn't support MTE_STORE_ONLY feature since other doesn't need to call hw_eanble_tag_checks_write_only() function -- it'll be failed so it is meaningless call. > > > As you said, kasan_flag_write_only reflects the state. > > But like other option, I keep the condition to call the hw_enable_xxx() > > by checking the "argments" and keep the "hw enable state" with > > kasan_flag_write_only. > > Assuming we keep this behavior, please add a comment explaining all this. Okay. :) -- Sincerely, Yeoreum Yun