From 5fbda3ecd14a5343644979c98d6eb65b7e7de9d8 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Wed, 18 Nov 2020 20:48:43 +0100 Subject: sched: highmem: Store local kmaps in task struct Instead of storing the map per CPU provide and use per task storage. That prepares for local kmaps which are preemptible. The context switch code is preparatory and not yet in use because kmap_atomic() runs with preemption disabled. Will be made usable in the next step. The context switch logic is safe even when an interrupt happens after clearing or before restoring the kmaps. The kmap index in task struct is not modified so any nesting kmap in an interrupt will use unused indices and on return the counter is the same as before. Also add an assert into the return to user space code. Going back to user space with an active kmap local is a nono. Signed-off-by: Thomas Gleixner Acked-by: Peter Zijlstra (Intel) Link: https://lore.kernel.org/r/20201118204007.372935758@linutronix.de --- include/linux/highmem-internal.h | 10 ++++++++++ include/linux/sched.h | 9 +++++++++ 2 files changed, 19 insertions(+) (limited to 'include/linux') diff --git a/include/linux/highmem-internal.h b/include/linux/highmem-internal.h index 6ceed907b14e..c5a22177db85 100644 --- a/include/linux/highmem-internal.h +++ b/include/linux/highmem-internal.h @@ -9,6 +9,16 @@ void *__kmap_local_pfn_prot(unsigned long pfn, pgprot_t prot); void *__kmap_local_page_prot(struct page *page, pgprot_t prot); void kunmap_local_indexed(void *vaddr); +void kmap_local_fork(struct task_struct *tsk); +void __kmap_local_sched_out(void); +void __kmap_local_sched_in(void); +static inline void kmap_assert_nomap(void) +{ + DEBUG_LOCKS_WARN_ON(current->kmap_ctrl.idx); +} +#else +static inline void kmap_local_fork(struct task_struct *tsk) { } +static inline void kmap_assert_nomap(void) { } #endif #ifdef CONFIG_HIGHMEM diff --git a/include/linux/sched.h b/include/linux/sched.h index a33f35f68060..8946911cee9f 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -34,6 +34,7 @@ #include #include #include +#include /* task_struct member predeclarations (sorted alphabetically): */ struct audit_context; @@ -629,6 +630,13 @@ struct wake_q_node { struct wake_q_node *next; }; +struct kmap_ctrl { +#ifdef CONFIG_KMAP_LOCAL + int idx; + pte_t pteval[KM_MAX_IDX]; +#endif +}; + struct task_struct { #ifdef CONFIG_THREAD_INFO_IN_TASK /* @@ -1294,6 +1302,7 @@ struct task_struct { unsigned int sequential_io; unsigned int sequential_io_avg; #endif + struct kmap_ctrl kmap_ctrl; #ifdef CONFIG_DEBUG_ATOMIC_SLEEP unsigned long task_state_change; #endif -- cgit v1.2.3