On Sun, Apr 03 2022 at 16:51, Max Filippov wrote:
> When CONFIG_DEBUG_KMAP_LOCAL is enabled __kmap_local_sched_{in,out}
> check that even slots in the tsk->kmap_ctrl.pteval are unmapped. The
> slots are initialized with 0 value, but the check is done with pte_none.
> 0 pte however does not necessarily mean that pte_none will return true.
> e.g. on xtensa it returns false, resulting in the following runtime
> warnings:
>
> WARNING: CPU: 0 PID: 101 at mm/highmem.c:627 __kmap_local_sched_out+0x51/0x108
> CPU: 0 PID: 101 Comm: touch Not tainted 5.17.0-rc7-00010-gd3a1cdde80d2-dirty #13
> Call Trace:
> dump_stack+0xc/0x40
> __warn+0x8f/0x174
> warn_slowpath_fmt+0x48/0xac
> __kmap_local_sched_out+0x51/0x108
> __schedule+0x71a/0x9c4
> preempt_schedule_irq+0xa0/0xe0
> common_exception_return+0x5c/0x93
> do_wp_page+0x30e/0x330
> handle_mm_fault+0xa70/0xc3c
> do_page_fault+0x1d8/0x3c4
> common_exception+0x7f/0x7f
>
> WARNING: CPU: 0 PID: 101 at mm/highmem.c:664 __kmap_local_sched_in+0x50/0xe0
> CPU: 0 PID: 101 Comm: touch Tainted: G W 5.17.0-rc7-00010-gd3a1cdde80d2-dirty #13
> Call Trace:
> dump_stack+0xc/0x40
> __warn+0x8f/0x174
> warn_slowpath_fmt+0x48/0xac
> __kmap_local_sched_in+0x50/0xe0
> finish_task_switch$isra$0+0x1ce/0x2f8
> __schedule+0x86e/0x9c4
> preempt_schedule_irq+0xa0/0xe0
> common_exception_return+0x5c/0x93
> do_wp_page+0x30e/0x330
> handle_mm_fault+0xa70/0xc3c
> do_page_fault+0x1d8/0x3c4
> common_exception+0x7f/0x7f
>
> Fix it by replacing !pte_none(pteval) with pte_val(pteval) != 0.
Oops. Sorry.
> Fixes: 5fbda3ecd14a ("sched: highmem: Store local kmaps in task struct")
> Signed-off-by: Max Filippov <jcmvbkbc@xxxxxxxxx>
Reviewed-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
