[patch V2 00/18] mm/highmem: Preemptible variant of kmap_atomic & friends

[patch V2 00/18] mm/highmem: Preemptible variant of kmap_atomic & friends

[Thomas Gleixner]

Following up to the discussion in:

  https://lore.kernel.org/r/20200914204209.256266093@linutronix.de

and the initial version of this:

  https://lore.kernel.org/r/20200919091751.011116649@linutronix.de

this series provides a preemptible variant of kmap_atomic & related
interfaces.

Now that the scheduler folks have wrapped their heads around the migration
disable scheduler woes, there is not a real reason anymore to confine
migration disabling to RT.

As expressed in the earlier discussion by graphics and crypto folks, there
is interest to get rid of their kmap_atomic* usage because they need only a
temporary stable map and not all the bells and whistels of kmap_atomic*.

This series provides kmap_local.* iomap_local variants which only disable
migration to keep the virtual mapping address stable accross preemption,
but do neither disable pagefaults nor preemption. The new functions can be
used in any context, but if used in atomic context the caller has to take
care of eventually disabling pagefaults.

This is achieved by:

 - Removing the RT dependency from migrate_disable/enable()

 - Consolidating all kmap atomic implementations in generic code

 - Switching from per CPU storage of the kmap index to a per task storage

 - Adding a pteval array to the per task storage which contains the ptevals
   of the currently active temporary kmaps

 - Adding context switch code which checks whether the outgoing or the
   incoming task has active temporary kmaps. If so, the outgoing task's
   kmaps are removed and the incoming task's kmaps are restored.

 - Adding new interfaces k[un]map_temporary*() which are not disabling
   preemption and can be called from any context (except NMI).

   Contrary to kmap() which provides preemptible and "persistant" mappings,
   these interfaces are meant to replace the temporary mappings provided by
   kmap_atomic*() today.

This allows to get rid of conditional mapping choices and allows to have
preemptible short term mappings on 64bit which are today enforced to be
non-preemptible due to the highmem constraints. It clearly puts overhead on
the highmem users, but highmem is slow anyway.

This is not a wholesale conversion which makes kmap_atomic magically
preemptible because there might be usage sites which rely on the implicit
preempt disable. So this needs to be done on a case by case basis and the
call sites converted to kmap_temporary.

Note, that this is only lightly tested on X86 and completely untested on
all other architectures.

There is also a still to be investigated question from Linus on the initial
posting versus the per cpu / per task mapping stack depth which might need
to be made larger due to the ability to take page faults within a mapping
region.

Though I wanted to share the current state of affairs before investigating
that further. If there is consensus in going forward with this, I'll have a
deeper look into this issue.

The lot is available from

   git://git.kernel.org/pub/scm/linux/kernel/git/tglx/devel.git highmem

It is based on Peter Zijlstras migrate disable branch which is close to be
merged into the tip tree, but still not finalized:

   git://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git sched/migrate-disable

Changes vs. V1:

  - Make it truly functional by depending on migrate disable/enable (Brown paperbag)
  - Rename to kmap_local.* (Linus)
  - Fix the sched in/out issue Linus pointed out
  - Fix a few style issues (Christoph)
  - Split a few things out into seperate patches to make review simpler
  - Pick up acked/reviewed tags as appropriate

Thanks,

	tglx
---
 a/arch/arm/mm/highmem.c               |  121 ------------------
 a/arch/microblaze/mm/highmem.c        |   78 ------------
 a/arch/nds32/mm/highmem.c             |   48 -------
 a/arch/powerpc/mm/highmem.c           |   67 ----------
 a/arch/sparc/mm/highmem.c             |  115 -----------------
 arch/arc/Kconfig                      |    1 
 arch/arc/include/asm/highmem.h        |    8 +
 arch/arc/mm/highmem.c                 |   44 ------
 arch/arm/Kconfig                      |    1 
 arch/arm/include/asm/highmem.h        |   31 +++-
 arch/arm/mm/Makefile                  |    1 
 arch/csky/Kconfig                     |    1 
 arch/csky/include/asm/highmem.h       |    4 
 arch/csky/mm/highmem.c                |   75 -----------
 arch/microblaze/Kconfig               |    1 
 arch/microblaze/include/asm/highmem.h |    6 
 arch/microblaze/mm/Makefile           |    1 
 arch/microblaze/mm/init.c             |    6 
 arch/mips/Kconfig                     |    1 
 arch/mips/include/asm/highmem.h       |    4 
 arch/mips/mm/highmem.c                |   77 ------------
 arch/mips/mm/init.c                   |    3 
 arch/nds32/Kconfig.cpu                |    1 
 arch/nds32/include/asm/highmem.h      |   21 ++-
 arch/nds32/mm/Makefile                |    1 
 arch/powerpc/Kconfig                  |    1 
 arch/powerpc/include/asm/highmem.h    |    6 
 arch/powerpc/mm/Makefile              |    1 
 arch/powerpc/mm/mem.c                 |    7 -
 arch/sparc/Kconfig                    |    1 
 arch/sparc/include/asm/highmem.h      |    7 -
 arch/sparc/mm/Makefile                |    3 
 arch/sparc/mm/srmmu.c                 |    2 
 arch/x86/include/asm/fixmap.h         |    1 
 arch/x86/include/asm/highmem.h        |   12 +
 arch/x86/include/asm/iomap.h          |   13 --
 arch/x86/mm/highmem_32.c              |   59 ---------
 arch/x86/mm/init_32.c                 |   15 --
 arch/x86/mm/iomap_32.c                |   57 --------
 arch/xtensa/Kconfig                   |    1 
 arch/xtensa/include/asm/highmem.h     |    9 +
 arch/xtensa/mm/highmem.c              |   44 ------
 b/arch/x86/Kconfig                    |    3 
 include/linux/highmem.h               |  203 ++++++++++++++++++++++---------
 include/linux/io-mapping.h            |   42 +++++-
 include/linux/preempt.h               |   38 -----
 include/linux/sched.h                 |   11 +
 kernel/entry/common.c                 |    2 
 kernel/fork.c                         |    1 
 kernel/sched/core.c                   |   30 +++-
 kernel/sched/sched.h                  |    2 
 lib/smp_processor_id.c                |    2 
 mm/Kconfig                            |    3 
 mm/highmem.c                          |  218 ++++++++++++++++++++++++++++++++--
 54 files changed, 542 insertions(+), 969 deletions(-)

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[patch V2 01/18] sched: Make migrate_disable/enable() independent of RT

[Thomas Gleixner]

Now that the scheduler can deal with migrate disable properly, there is no
real compelling reason to make it only available for RT.

There are quite some code pathes which needlessly disable preemption in
order to prevent migration and some constructs like kmap_atomic() enforce
it implicitly.

Making it available independent of RT allows to provide a preemptible
variant of kmap_atomic() and makes the code more consistent in general.

FIXME: Rework the comment in preempt.h

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Ben Segall <bsegall@google.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Daniel Bristot de Oliveira <bristot@redhat.com>
---
 include/linux/preempt.h |   38 +++-----------------------------------
 include/linux/sched.h   |    2 +-
 kernel/sched/core.c     |   12 ++----------
 kernel/sched/sched.h    |    2 +-
 lib/smp_processor_id.c  |    2 +-
 5 files changed, 8 insertions(+), 48 deletions(-)

--- a/include/linux/preempt.h
+++ b/include/linux/preempt.h
@@ -322,7 +322,7 @@ static inline void preempt_notifier_init
 
 #endif
 
-#if defined(CONFIG_SMP) && defined(CONFIG_PREEMPT_RT)
+#ifdef CONFIG_SMP
 
 /*
  * Migrate-Disable and why it is undesired.
@@ -382,43 +382,11 @@ static inline void preempt_notifier_init
 extern void migrate_disable(void);
 extern void migrate_enable(void);
 
-#elif defined(CONFIG_PREEMPT_RT)
+#else
 
 static inline void migrate_disable(void) { }
 static inline void migrate_enable(void) { }
 
-#else /* !CONFIG_PREEMPT_RT */
-
-/**
- * migrate_disable - Prevent migration of the current task
- *
- * Maps to preempt_disable() which also disables preemption. Use
- * migrate_disable() to annotate that the intent is to prevent migration,
- * but not necessarily preemption.
- *
- * Can be invoked nested like preempt_disable() and needs the corresponding
- * number of migrate_enable() invocations.
- */
-static __always_inline void migrate_disable(void)
-{
-	preempt_disable();
-}
-
-/**
- * migrate_enable - Allow migration of the current task
- *
- * Counterpart to migrate_disable().
- *
- * As migrate_disable() can be invoked nested, only the outermost invocation
- * reenables migration.
- *
- * Currently mapped to preempt_enable().
- */
-static __always_inline void migrate_enable(void)
-{
-	preempt_enable();
-}
-
-#endif /* CONFIG_SMP && CONFIG_PREEMPT_RT */
+#endif /* CONFIG_SMP */
 
 #endif /* __LINUX_PREEMPT_H */
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -715,7 +715,7 @@ struct task_struct {
 	const cpumask_t			*cpus_ptr;
 	cpumask_t			cpus_mask;
 	void				*migration_pending;
-#if defined(CONFIG_SMP) && defined(CONFIG_PREEMPT_RT)
+#ifdef CONFIG_SMP
 	unsigned short			migration_disabled;
 #endif
 	unsigned short			migration_flags;
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1696,8 +1696,6 @@ void check_preempt_curr(struct rq *rq, s
 
 #ifdef CONFIG_SMP
 
-#ifdef CONFIG_PREEMPT_RT
-
 static void
 __do_set_cpus_allowed(struct task_struct *p, const struct cpumask *new_mask, u32 flags);
 
@@ -1772,8 +1770,6 @@ static inline bool rq_has_pinned_tasks(s
 	return rq->nr_pinned;
 }
 
-#endif
-
 /*
  * Per-CPU kthreads are allowed to run on !active && online CPUs, see
  * __set_cpus_allowed_ptr() and select_fallback_rq().
@@ -2841,7 +2837,7 @@ void sched_set_stop_task(int cpu, struct
 	}
 }
 
-#else
+#else /* CONFIG_SMP */
 
 static inline int __set_cpus_allowed_ptr(struct task_struct *p,
 					 const struct cpumask *new_mask,
@@ -2850,10 +2846,6 @@ static inline int __set_cpus_allowed_ptr
 	return set_cpus_allowed_ptr(p, new_mask);
 }
 
-#endif /* CONFIG_SMP */
-
-#if !defined(CONFIG_SMP) || !defined(CONFIG_PREEMPT_RT)
-
 static inline void migrate_disable_switch(struct rq *rq, struct task_struct *p) { }
 
 static inline bool rq_has_pinned_tasks(struct rq *rq)
@@ -2861,7 +2853,7 @@ static inline bool rq_has_pinned_tasks(s
 	return false;
 }
 
-#endif
+#endif /* !CONFIG_SMP */
 
 static void
 ttwu_stat(struct task_struct *p, int cpu, int wake_flags)
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -1056,7 +1056,7 @@ struct rq {
 	struct cpuidle_state	*idle_state;
 #endif
 
-#if defined(CONFIG_PREEMPT_RT) && defined(CONFIG_SMP)
+#if CONFIG_SMP
 	unsigned int		nr_pinned;
 #endif
 	unsigned int		push_busy;
--- a/lib/smp_processor_id.c
+++ b/lib/smp_processor_id.c
@@ -26,7 +26,7 @@ unsigned int check_preemption_disabled(c
 	if (current->nr_cpus_allowed == 1)
 		goto out;
 
-#if defined(CONFIG_SMP) && defined(CONFIG_PREEMPT_RT)
+#ifdef CONFIG_SMP
 	if (current->migration_disabled)
 		goto out;
 #endif


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[patch V2 02/18] mm/highmem: Un-EXPORT __kmap_atomic_idx()

[Thomas Gleixner]

Nothing in modules can use that.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-mm@kvack.org
---
 mm/highmem.c |    2 --
 1 file changed, 2 deletions(-)

--- a/mm/highmem.c
+++ b/mm/highmem.c
@@ -108,8 +108,6 @@ static inline wait_queue_head_t *get_pkm
 atomic_long_t _totalhigh_pages __read_mostly;
 EXPORT_SYMBOL(_totalhigh_pages);
 
-EXPORT_PER_CPU_SYMBOL(__kmap_atomic_idx);
-
 unsigned int nr_free_highpages (void)
 {
 	struct zone *zone;


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[patch V2 03/18] highmem: Provide generic variant of kmap_atomic*

[Thomas Gleixner]

The kmap_atomic* interfaces in all architectures are pretty much the same
except for post map operations (flush) and pre- and post unmap operations.

Provide a generic variant for that.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-mm@kvack.org
---
V2: Address review comments from Christoph (style and EXPORT variant)
---
 include/linux/highmem.h |   79 ++++++++++++++++++++++++++------
 mm/Kconfig              |    3 +
 mm/highmem.c            |  118 +++++++++++++++++++++++++++++++++++++++++++++++-
 3 files changed, 183 insertions(+), 17 deletions(-)

--- a/include/linux/highmem.h
+++ b/include/linux/highmem.h
@@ -31,9 +31,16 @@ static inline void invalidate_kernel_vma
 
 #include <asm/kmap_types.h>
 
+/*
+ * Outside of CONFIG_HIGHMEM to support X86 32bit iomap_atomic() cruft.
+ */
+#ifdef CONFIG_KMAP_LOCAL
+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);
+#endif
+
 #ifdef CONFIG_HIGHMEM
-extern void *kmap_atomic_high_prot(struct page *page, pgprot_t prot);
-extern void kunmap_atomic_high(void *kvaddr);
 #include <asm/highmem.h>
 
 #ifndef ARCH_HAS_KMAP_FLUSH_TLB
@@ -81,6 +88,11 @@ static inline void kunmap(struct page *p
  * be used in IRQ contexts, so in some (very limited) cases we need
  * it.
  */
+
+#ifndef CONFIG_KMAP_LOCAL
+void *kmap_atomic_high_prot(struct page *page, pgprot_t prot);
+void kunmap_atomic_high(void *kvaddr);
+
 static inline void *kmap_atomic_prot(struct page *page, pgprot_t prot)
 {
 	preempt_disable();
@@ -89,7 +101,38 @@ static inline void *kmap_atomic_prot(str
 		return page_address(page);
 	return kmap_atomic_high_prot(page, prot);
 }
-#define kmap_atomic(page)	kmap_atomic_prot(page, kmap_prot)
+
+static inline void __kunmap_atomic(void *vaddr)
+{
+	kunmap_atomic_high(vaddr);
+}
+#else /* !CONFIG_KMAP_LOCAL */
+
+static inline void *kmap_atomic_prot(struct page *page, pgprot_t prot)
+{
+	preempt_disable();
+	pagefault_disable();
+	return __kmap_local_page_prot(page, prot);
+}
+
+static inline void *kmap_atomic_pfn(unsigned long pfn)
+{
+	preempt_disable();
+	pagefault_disable();
+	return __kmap_local_pfn_prot(pfn, kmap_prot);
+}
+
+static inline void __kunmap_atomic(void *addr)
+{
+	kunmap_local_indexed(addr);
+}
+
+#endif /* CONFIG_KMAP_LOCAL */
+
+static inline void *kmap_atomic(struct page *page)
+{
+	return kmap_atomic_prot(page, kmap_prot);
+}
 
 /* declarations for linux/mm/highmem.c */
 unsigned int nr_free_highpages(void);
@@ -157,21 +200,28 @@ static inline void *kmap_atomic(struct p
 	pagefault_disable();
 	return page_address(page);
 }
-#define kmap_atomic_prot(page, prot)	kmap_atomic(page)
 
-static inline void kunmap_atomic_high(void *addr)
+static inline void *kmap_atomic_prot(struct page *page, pgprot_t prot)
+{
+	return kmap_atomic(page);
+}
+
+static inline void *kmap_atomic_pfn(unsigned long pfn)
+{
+	return kmap_atomic(pfn_to_page(pfn));
+}
+
+static inline void __kunmap_atomic(void *addr)
 {
 	/*
 	 * Mostly nothing to do in the CONFIG_HIGHMEM=n case as kunmap_atomic()
-	 * handles re-enabling faults + preemption
+	 * handles re-enabling faults and preemption
 	 */
 #ifdef ARCH_HAS_FLUSH_ON_KUNMAP
 	kunmap_flush_on_unmap(addr);
 #endif
 }
 
-#define kmap_atomic_pfn(pfn)	kmap_atomic(pfn_to_page(pfn))
-
 #define kmap_flush_unused()	do {} while(0)
 
 #endif /* CONFIG_HIGHMEM */
@@ -213,15 +263,14 @@ static inline void kmap_atomic_idx_pop(v
  * Prevent people trying to call kunmap_atomic() as if it were kunmap()
  * kunmap_atomic() should get the return value of kmap_atomic, not the page.
  */
-#define kunmap_atomic(addr)                                     \
-do {                                                            \
-	BUILD_BUG_ON(__same_type((addr), struct page *));       \
-	kunmap_atomic_high(addr);                                  \
-	pagefault_enable();                                     \
-	preempt_enable();                                       \
+#define kunmap_atomic(__addr)					\
+do {								\
+	BUILD_BUG_ON(__same_type((__addr), struct page *));	\
+	__kunmap_atomic(__addr);				\
+	pagefault_enable();					\
+	preempt_enable();					\
 } while (0)
 
-
 /* when CONFIG_HIGHMEM is not set these will be plain clear/copy_page */
 #ifndef clear_user_highpage
 static inline void clear_user_highpage(struct page *page, unsigned long vaddr)
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -872,4 +872,7 @@ config ARCH_HAS_HUGEPD
 config MAPPING_DIRTY_HELPERS
         bool
 
+config KMAP_LOCAL
+	bool
+
 endmenu
--- a/mm/highmem.c
+++ b/mm/highmem.c
@@ -30,6 +30,7 @@
 #include <linux/kgdb.h>
 #include <asm/tlbflush.h>
 #include <linux/vmalloc.h>
+#include <asm/fixmap.h>
 
 #if defined(CONFIG_HIGHMEM) || defined(CONFIG_X86_32)
 DEFINE_PER_CPU(int, __kmap_atomic_idx);
@@ -365,9 +366,122 @@ void kunmap_high(struct page *page)
 	if (need_wakeup)
 		wake_up(pkmap_map_wait);
 }
-
 EXPORT_SYMBOL(kunmap_high);
-#endif	/* CONFIG_HIGHMEM */
+#endif /* CONFIG_HIGHMEM */
+
+#ifdef CONFIG_KMAP_LOCAL
+#ifndef arch_kmap_local_post_map
+# define arch_kmap_local_post_map(vaddr, pteval)	do { } while (0)
+#endif
+
+#ifndef arch_kmap_local_pre_unmap
+# define arch_kmap_local_pre_unmap(vaddr)		do { } while (0)
+#endif
+
+#ifndef arch_kmap_local_post_unmap
+# define arch_kmap_local_post_unmap(vaddr)		do { } while (0)
+#endif
+
+#ifndef arch_kmap_local_map_idx
+#define arch_kmap_local_map_idx(type, pfn)	kmap_local_calc_idx(type)
+#endif
+
+#ifndef arch_kmap_local_unmap_idx
+#define arch_kmap_local_unmap_idx(type, vaddr)	kmap_local_calc_idx(type)
+#endif
+
+#ifndef arch_kmap_local_high_get
+static inline void *arch_kmap_local_high_get(struct page *page)
+{
+	return NULL;
+}
+#endif
+
+/* Unmap a local mapping which was obtained by kmap_high_get() */
+static inline void kmap_high_unmap_local(unsigned long vaddr)
+{
+#ifdef ARCH_NEEDS_KMAP_HIGH_GET
+	if (vaddr >= PKMAP_ADDR(0) && vaddr < PKMAP_ADDR(LAST_PKMAP))
+		kunmap_high(pte_page(pkmap_page_table[PKMAP_NR(vaddr)]));
+#endif
+}
+
+static inline int kmap_local_calc_idx(int type)
+{
+	return type + KM_TYPE_NR * smp_processor_id();
+}
+
+static pte_t *__kmap_pte;
+
+static pte_t *kmap_get_pte(void)
+{
+	if (!__kmap_pte)
+		__kmap_pte = virt_to_kpte(__fix_to_virt(FIX_KMAP_BEGIN));
+	return __kmap_pte;
+}
+
+void *__kmap_local_pfn_prot(unsigned long pfn, pgprot_t prot)
+{
+	pte_t pteval, *kmap_pte = kmap_get_pte();
+	unsigned long vaddr;
+	int idx;
+
+	preempt_disable();
+	idx = arch_kmap_local_map_idx(kmap_atomic_idx_push(), pfn);
+	vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
+	BUG_ON(!pte_none(*(kmap_pte - idx)));
+	pteval = pfn_pte(pfn, prot);
+	set_pte_at(&init_mm, vaddr, kmap_pte - idx, pteval);
+	arch_kmap_local_post_map(vaddr, pteval);
+	preempt_enable();
+
+	return (void *)vaddr;
+}
+EXPORT_SYMBOL_GPL(__kmap_local_pfn_prot);
+
+void *__kmap_local_page_prot(struct page *page, pgprot_t prot)
+{
+	void *kmap;
+
+	if (!PageHighMem(page))
+		return page_address(page);
+
+	/* Try kmap_high_get() if architecture has it enabled */
+	kmap = arch_kmap_local_high_get(page);
+	if (kmap)
+		return kmap;
+
+	return __kmap_local_pfn_prot(page_to_pfn(page), prot);
+}
+EXPORT_SYMBOL(__kmap_local_page_prot);
+
+void kunmap_local_indexed(void *vaddr)
+{
+	unsigned long addr = (unsigned long) vaddr & PAGE_MASK;
+	pte_t *kmap_pte = kmap_get_pte();
+	int idx;
+
+	if (addr < __fix_to_virt(FIX_KMAP_END) ||
+	    addr > __fix_to_virt(FIX_KMAP_BEGIN)) {
+		WARN_ON_ONCE(addr < PAGE_OFFSET);
+
+		/* Handle mappings which were obtained by kmap_high_get() */
+		kmap_high_unmap_local(addr);
+		return;
+	}
+
+	preempt_disable();
+	idx = arch_kmap_local_unmap_idx(kmap_atomic_idx(), addr);
+	WARN_ON_ONCE(addr != __fix_to_virt(FIX_KMAP_BEGIN + idx));
+
+	arch_kmap_local_pre_unmap(addr);
+	pte_clear(&init_mm, addr, kmap_pte - idx);
+	arch_kmap_local_post_unmap(addr);
+	kmap_atomic_idx_pop();
+	preempt_enable();
+}
+EXPORT_SYMBOL(kunmap_local_indexed);
+#endif
 
 #if defined(HASHED_PAGE_VIRTUAL)
 


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[patch V2 04/18] x86/mm/highmem: Use generic kmap atomic implementation

[Thomas Gleixner]

Convert X86 to the generic kmap atomic implementation and make the
iomap_atomic() naming convention consistent while at it.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: x86@kernel.org
---
 arch/x86/Kconfig               |    3 +-
 arch/x86/include/asm/fixmap.h  |    1 
 arch/x86/include/asm/highmem.h |   12 ++++++--
 arch/x86/include/asm/iomap.h   |   18 ++++++------
 arch/x86/mm/highmem_32.c       |   59 -----------------------------------------
 arch/x86/mm/init_32.c          |   15 ----------
 arch/x86/mm/iomap_32.c         |   59 +++--------------------------------------
 include/linux/io-mapping.h     |    2 -
 8 files changed, 27 insertions(+), 142 deletions(-)

--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -14,10 +14,11 @@ config X86_32
 	select ARCH_WANT_IPC_PARSE_VERSION
 	select CLKSRC_I8253
 	select CLONE_BACKWARDS
+	select GENERIC_VDSO_32
 	select HAVE_DEBUG_STACKOVERFLOW
+	select KMAP_LOCAL
 	select MODULES_USE_ELF_REL
 	select OLD_SIGACTION
-	select GENERIC_VDSO_32
 
 config X86_64
 	def_bool y
--- a/arch/x86/include/asm/fixmap.h
+++ b/arch/x86/include/asm/fixmap.h
@@ -151,7 +151,6 @@ extern void reserve_top_address(unsigned
 
 extern int fixmaps_set;
 
-extern pte_t *kmap_pte;
 extern pte_t *pkmap_page_table;
 
 void __native_set_fixmap(enum fixed_addresses idx, pte_t pte);
--- a/arch/x86/include/asm/highmem.h
+++ b/arch/x86/include/asm/highmem.h
@@ -58,11 +58,17 @@ extern unsigned long highstart_pfn, high
 #define PKMAP_NR(virt)  ((virt-PKMAP_BASE) >> PAGE_SHIFT)
 #define PKMAP_ADDR(nr)  (PKMAP_BASE + ((nr) << PAGE_SHIFT))
 
-void *kmap_atomic_pfn(unsigned long pfn);
-void *kmap_atomic_prot_pfn(unsigned long pfn, pgprot_t prot);
-
 #define flush_cache_kmaps()	do { } while (0)
 
+#define	arch_kmap_local_post_map(vaddr, pteval)		\
+	arch_flush_lazy_mmu_mode()
+
+#define	arch_kmap_local_post_unmap(vaddr)		\
+	do {						\
+		flush_tlb_one_kernel((vaddr));		\
+		arch_flush_lazy_mmu_mode();		\
+	} while (0)
+
 extern void add_highpages_with_active_regions(int nid, unsigned long start_pfn,
 					unsigned long end_pfn);
 
--- a/arch/x86/include/asm/iomap.h
+++ b/arch/x86/include/asm/iomap.h
@@ -9,19 +9,21 @@
 #include <linux/fs.h>
 #include <linux/mm.h>
 #include <linux/uaccess.h>
+#include <linux/highmem.h>
 #include <asm/cacheflush.h>
 #include <asm/tlbflush.h>
 
-void __iomem *
-iomap_atomic_prot_pfn(unsigned long pfn, pgprot_t prot);
+void __iomem *iomap_atomic_pfn_prot(unsigned long pfn, pgprot_t prot);
 
-void
-iounmap_atomic(void __iomem *kvaddr);
+static inline void iounmap_atomic(void __iomem *vaddr)
+{
+	kunmap_local_indexed((void __force *)vaddr);
+	pagefault_enable();
+	preempt_enable();
+}
 
-int
-iomap_create_wc(resource_size_t base, unsigned long size, pgprot_t *prot);
+int iomap_create_wc(resource_size_t base, unsigned long size, pgprot_t *prot);
 
-void
-iomap_free(resource_size_t base, unsigned long size);
+void iomap_free(resource_size_t base, unsigned long size);
 
 #endif /* _ASM_X86_IOMAP_H */
--- a/arch/x86/mm/highmem_32.c
+++ b/arch/x86/mm/highmem_32.c
@@ -4,65 +4,6 @@
 #include <linux/swap.h> /* for totalram_pages */
 #include <linux/memblock.h>
 
-void *kmap_atomic_high_prot(struct page *page, pgprot_t prot)
-{
-	unsigned long vaddr;
-	int idx, type;
-
-	type = kmap_atomic_idx_push();
-	idx = type + KM_TYPE_NR*smp_processor_id();
-	vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
-	BUG_ON(!pte_none(*(kmap_pte-idx)));
-	set_pte(kmap_pte-idx, mk_pte(page, prot));
-	arch_flush_lazy_mmu_mode();
-
-	return (void *)vaddr;
-}
-EXPORT_SYMBOL(kmap_atomic_high_prot);
-
-/*
- * This is the same as kmap_atomic() but can map memory that doesn't
- * have a struct page associated with it.
- */
-void *kmap_atomic_pfn(unsigned long pfn)
-{
-	return kmap_atomic_prot_pfn(pfn, kmap_prot);
-}
-EXPORT_SYMBOL_GPL(kmap_atomic_pfn);
-
-void kunmap_atomic_high(void *kvaddr)
-{
-	unsigned long vaddr = (unsigned long) kvaddr & PAGE_MASK;
-
-	if (vaddr >= __fix_to_virt(FIX_KMAP_END) &&
-	    vaddr <= __fix_to_virt(FIX_KMAP_BEGIN)) {
-		int idx, type;
-
-		type = kmap_atomic_idx();
-		idx = type + KM_TYPE_NR * smp_processor_id();
-
-#ifdef CONFIG_DEBUG_HIGHMEM
-		WARN_ON_ONCE(vaddr != __fix_to_virt(FIX_KMAP_BEGIN + idx));
-#endif
-		/*
-		 * Force other mappings to Oops if they'll try to access this
-		 * pte without first remap it.  Keeping stale mappings around
-		 * is a bad idea also, in case the page changes cacheability
-		 * attributes or becomes a protected page in a hypervisor.
-		 */
-		kpte_clear_flush(kmap_pte-idx, vaddr);
-		kmap_atomic_idx_pop();
-		arch_flush_lazy_mmu_mode();
-	}
-#ifdef CONFIG_DEBUG_HIGHMEM
-	else {
-		BUG_ON(vaddr < PAGE_OFFSET);
-		BUG_ON(vaddr >= (unsigned long)high_memory);
-	}
-#endif
-}
-EXPORT_SYMBOL(kunmap_atomic_high);
-
 void __init set_highmem_pages_init(void)
 {
 	struct zone *zone;
--- a/arch/x86/mm/init_32.c
+++ b/arch/x86/mm/init_32.c
@@ -394,19 +394,6 @@ kernel_physical_mapping_init(unsigned lo
 	return last_map_addr;
 }
 
-pte_t *kmap_pte;
-
-static void __init kmap_init(void)
-{
-	unsigned long kmap_vstart;
-
-	/*
-	 * Cache the first kmap pte:
-	 */
-	kmap_vstart = __fix_to_virt(FIX_KMAP_BEGIN);
-	kmap_pte = virt_to_kpte(kmap_vstart);
-}
-
 #ifdef CONFIG_HIGHMEM
 static void __init permanent_kmaps_init(pgd_t *pgd_base)
 {
@@ -712,8 +699,6 @@ void __init paging_init(void)
 
 	__flush_tlb_all();
 
-	kmap_init();
-
 	/*
 	 * NOTE: at this point the bootmem allocator is fully available.
 	 */
--- a/arch/x86/mm/iomap_32.c
+++ b/arch/x86/mm/iomap_32.c
@@ -44,28 +44,7 @@ void iomap_free(resource_size_t base, un
 }
 EXPORT_SYMBOL_GPL(iomap_free);
 
-void *kmap_atomic_prot_pfn(unsigned long pfn, pgprot_t prot)
-{
-	unsigned long vaddr;
-	int idx, type;
-
-	preempt_disable();
-	pagefault_disable();
-
-	type = kmap_atomic_idx_push();
-	idx = type + KM_TYPE_NR * smp_processor_id();
-	vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
-	set_pte(kmap_pte - idx, pfn_pte(pfn, prot));
-	arch_flush_lazy_mmu_mode();
-
-	return (void *)vaddr;
-}
-
-/*
- * Map 'pfn' using protections 'prot'
- */
-void __iomem *
-iomap_atomic_prot_pfn(unsigned long pfn, pgprot_t prot)
+void __iomem *iomap_atomic_pfn_prot(unsigned long pfn, pgprot_t prot)
 {
 	/*
 	 * For non-PAT systems, translate non-WB request to UC- just in
@@ -81,36 +60,8 @@ iomap_atomic_prot_pfn(unsigned long pfn,
 	/* Filter out unsupported __PAGE_KERNEL* bits: */
 	pgprot_val(prot) &= __default_kernel_pte_mask;
 
-	return (void __force __iomem *) kmap_atomic_prot_pfn(pfn, prot);
-}
-EXPORT_SYMBOL_GPL(iomap_atomic_prot_pfn);
-
-void
-iounmap_atomic(void __iomem *kvaddr)
-{
-	unsigned long vaddr = (unsigned long) kvaddr & PAGE_MASK;
-
-	if (vaddr >= __fix_to_virt(FIX_KMAP_END) &&
-	    vaddr <= __fix_to_virt(FIX_KMAP_BEGIN)) {
-		int idx, type;
-
-		type = kmap_atomic_idx();
-		idx = type + KM_TYPE_NR * smp_processor_id();
-
-#ifdef CONFIG_DEBUG_HIGHMEM
-		WARN_ON_ONCE(vaddr != __fix_to_virt(FIX_KMAP_BEGIN + idx));
-#endif
-		/*
-		 * Force other mappings to Oops if they'll try to access this
-		 * pte without first remap it.  Keeping stale mappings around
-		 * is a bad idea also, in case the page changes cacheability
-		 * attributes or becomes a protected page in a hypervisor.
-		 */
-		kpte_clear_flush(kmap_pte-idx, vaddr);
-		kmap_atomic_idx_pop();
-	}
-
-	pagefault_enable();
-	preempt_enable();
+	preempt_disable();
+	pagefault_disable();
+	return (void __force __iomem *)__kmap_local_pfn_prot(pfn, prot);
 }
-EXPORT_SYMBOL_GPL(iounmap_atomic);
+EXPORT_SYMBOL_GPL(iomap_atomic_pfn_prot);
--- a/include/linux/io-mapping.h
+++ b/include/linux/io-mapping.h
@@ -69,7 +69,7 @@ io_mapping_map_atomic_wc(struct io_mappi
 
 	BUG_ON(offset >= mapping->size);
 	phys_addr = mapping->base + offset;
-	return iomap_atomic_prot_pfn(PHYS_PFN(phys_addr), mapping->prot);
+	return iomap_atomic_pfn_prot(PHYS_PFN(phys_addr), mapping->prot);
 }
 
 static inline void


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[patch V2 05/18] arc/mm/highmem: Use generic kmap atomic implementation

[Thomas Gleixner]

Adopt the map ordering to match the other architectures and the generic
code.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Vineet Gupta <vgupta@synopsys.com>
Cc: linux-snps-arc@lists.infradead.org
---
 arch/arc/Kconfig               |    1 
 arch/arc/include/asm/highmem.h |    8 ++++++-
 arch/arc/mm/highmem.c          |   44 -----------------------------------------
 3 files changed, 9 insertions(+), 44 deletions(-)

--- a/arch/arc/Kconfig
+++ b/arch/arc/Kconfig
@@ -507,6 +507,7 @@ config LINUX_RAM_BASE
 config HIGHMEM
 	bool "High Memory Support"
 	select ARCH_DISCONTIGMEM_ENABLE
+	select KMAP_LOCAL
 	help
 	  With ARC 2G:2G address split, only upper 2G is directly addressable by
 	  kernel. Enable this to potentially allow access to rest of 2G and PAE
--- a/arch/arc/include/asm/highmem.h
+++ b/arch/arc/include/asm/highmem.h
@@ -15,7 +15,10 @@
 #define FIXMAP_BASE		(PAGE_OFFSET - FIXMAP_SIZE - PKMAP_SIZE)
 #define FIXMAP_SIZE		PGDIR_SIZE	/* only 1 PGD worth */
 #define KM_TYPE_NR		((FIXMAP_SIZE >> PAGE_SHIFT)/NR_CPUS)
-#define FIXMAP_ADDR(nr)		(FIXMAP_BASE + ((nr) << PAGE_SHIFT))
+
+#define FIX_KMAP_BEGIN		(0)
+#define FIX_KMAP_END		((FIXMAP_SIZE >> PAGE_SHIFT) - 1)
+#define FIXADDR_TOP		(FIXMAP_BASE + FIXMAP_SIZE - PAGE_SIZE)
 
 /* start after fixmap area */
 #define PKMAP_BASE		(FIXMAP_BASE + FIXMAP_SIZE)
@@ -29,6 +32,9 @@
 
 extern void kmap_init(void);
 
+#define arch_kmap_local_post_unmap(vaddr)			\
+	local_flush_tlb_kernel_range(vaddr, vaddr + PAGE_SIZE)
+
 static inline void flush_cache_kmaps(void)
 {
 	flush_cache_all();
--- a/arch/arc/mm/highmem.c
+++ b/arch/arc/mm/highmem.c
@@ -47,48 +47,6 @@
  */
 
 extern pte_t * pkmap_page_table;
-static pte_t * fixmap_page_table;
-
-void *kmap_atomic_high_prot(struct page *page, pgprot_t prot)
-{
-	int idx, cpu_idx;
-	unsigned long vaddr;
-
-	cpu_idx = kmap_atomic_idx_push();
-	idx = cpu_idx + KM_TYPE_NR * smp_processor_id();
-	vaddr = FIXMAP_ADDR(idx);
-
-	set_pte_at(&init_mm, vaddr, fixmap_page_table + idx,
-		   mk_pte(page, prot));
-
-	return (void *)vaddr;
-}
-EXPORT_SYMBOL(kmap_atomic_high_prot);
-
-void kunmap_atomic_high(void *kv)
-{
-	unsigned long kvaddr = (unsigned long)kv;
-
-	if (kvaddr >= FIXMAP_BASE && kvaddr < (FIXMAP_BASE + FIXMAP_SIZE)) {
-
-		/*
-		 * Because preemption is disabled, this vaddr can be associated
-		 * with the current allocated index.
-		 * But in case of multiple live kmap_atomic(), it still relies on
-		 * callers to unmap in right order.
-		 */
-		int cpu_idx = kmap_atomic_idx();
-		int idx = cpu_idx + KM_TYPE_NR * smp_processor_id();
-
-		WARN_ON(kvaddr != FIXMAP_ADDR(idx));
-
-		pte_clear(&init_mm, kvaddr, fixmap_page_table + idx);
-		local_flush_tlb_kernel_range(kvaddr, kvaddr + PAGE_SIZE);
-
-		kmap_atomic_idx_pop();
-	}
-}
-EXPORT_SYMBOL(kunmap_atomic_high);
 
 static noinline pte_t * __init alloc_kmap_pgtable(unsigned long kvaddr)
 {
@@ -113,5 +71,5 @@ void __init kmap_init(void)
 	pkmap_page_table = alloc_kmap_pgtable(PKMAP_BASE);
 
 	BUILD_BUG_ON(LAST_PKMAP > PTRS_PER_PTE);
-	fixmap_page_table = alloc_kmap_pgtable(FIXMAP_BASE);
+	alloc_kmap_pgtable(FIXMAP_BASE);
 }


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[patch V2 06/18] ARM: highmem: Switch to generic kmap atomic

[Thomas Gleixner]

No reason having the same code in every architecture.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: linux-arm-kernel@lists.infradead.org

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index e00d94b16658..410235e350cc 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -1499,6 +1499,7 @@ config HAVE_ARCH_PFN_VALID
 config HIGHMEM
 	bool "High Memory Support"
 	depends on MMU
+	select KMAP_LOCAL
 	help
 	  The address space of ARM processors is only 4 Gigabytes large
 	  and it has to accommodate user address space, kernel address
diff --git a/arch/arm/include/asm/highmem.h b/arch/arm/include/asm/highmem.h
index 31811be38d78..99a99862c474 100644
--- a/arch/arm/include/asm/highmem.h
+++ b/arch/arm/include/asm/highmem.h
@@ -46,19 +46,32 @@ extern pte_t *pkmap_page_table;
 
 #ifdef ARCH_NEEDS_KMAP_HIGH_GET
 extern void *kmap_high_get(struct page *page);
-#else
+
+static inline void *arch_kmap_local_high_get(struct page *page)
+{
+	if (IS_ENABLED(CONFIG_DEBUG_HIGHMEM) && !cache_is_vivt())
+		return NULL;
+	return kmap_high_get(page);
+}
+#define arch_kmap_local_high_get arch_kmap_local_high_get
+
+#else /* ARCH_NEEDS_KMAP_HIGH_GET */
 static inline void *kmap_high_get(struct page *page)
 {
 	return NULL;
 }
-#endif
+#endif /* !ARCH_NEEDS_KMAP_HIGH_GET */
 
-/*
- * The following functions are already defined by <linux/highmem.h>
- * when CONFIG_HIGHMEM is not set.
- */
-#ifdef CONFIG_HIGHMEM
-extern void *kmap_atomic_pfn(unsigned long pfn);
-#endif
+#define arch_kmap_local_post_map(vaddr, pteval)				\
+	local_flush_tlb_kernel_page(vaddr)
+
+#define arch_kmap_local_pre_unmap(vaddr)				\
+do {									\
+	if (cache_is_vivt())						\
+		__cpuc_flush_dcache_area((void *)vaddr, PAGE_SIZE);	\
+} while (0)
+
+#define arch_kmap_local_post_unmap(vaddr)				\
+	local_flush_tlb_kernel_page(vaddr)
 
 #endif
diff --git a/arch/arm/mm/Makefile b/arch/arm/mm/Makefile
index 7cb1699fbfc4..c4ce477c5261 100644
--- a/arch/arm/mm/Makefile
+++ b/arch/arm/mm/Makefile
@@ -19,7 +19,6 @@ obj-$(CONFIG_MODULES)		+= proc-syms.o
 obj-$(CONFIG_DEBUG_VIRTUAL)	+= physaddr.o
 
 obj-$(CONFIG_ALIGNMENT_TRAP)	+= alignment.o
-obj-$(CONFIG_HIGHMEM)		+= highmem.o
 obj-$(CONFIG_HUGETLB_PAGE)	+= hugetlbpage.o
 obj-$(CONFIG_ARM_PV_FIXUP)	+= pv-fixup-asm.o
 
diff --git a/arch/arm/mm/highmem.c b/arch/arm/mm/highmem.c
deleted file mode 100644
index 187fab227b50..000000000000
--- a/arch/arm/mm/highmem.c
+++ /dev/null
@@ -1,121 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0-only
-/*
- * arch/arm/mm/highmem.c -- ARM highmem support
- *
- * Author:	Nicolas Pitre
- * Created:	september 8, 2008
- * Copyright:	Marvell Semiconductors Inc.
- */
-
-#include <linux/module.h>
-#include <linux/highmem.h>
-#include <linux/interrupt.h>
-#include <asm/fixmap.h>
-#include <asm/cacheflush.h>
-#include <asm/tlbflush.h>
-#include "mm.h"
-
-static inline void set_fixmap_pte(int idx, pte_t pte)
-{
-	unsigned long vaddr = __fix_to_virt(idx);
-	pte_t *ptep = virt_to_kpte(vaddr);
-
-	set_pte_ext(ptep, pte, 0);
-	local_flush_tlb_kernel_page(vaddr);
-}
-
-static inline pte_t get_fixmap_pte(unsigned long vaddr)
-{
-	pte_t *ptep = virt_to_kpte(vaddr);
-
-	return *ptep;
-}
-
-void *kmap_atomic_high_prot(struct page *page, pgprot_t prot)
-{
-	unsigned int idx;
-	unsigned long vaddr;
-	void *kmap;
-	int type;
-
-#ifdef CONFIG_DEBUG_HIGHMEM
-	/*
-	 * There is no cache coherency issue when non VIVT, so force the
-	 * dedicated kmap usage for better debugging purposes in that case.
-	 */
-	if (!cache_is_vivt())
-		kmap = NULL;
-	else
-#endif
-		kmap = kmap_high_get(page);
-	if (kmap)
-		return kmap;
-
-	type = kmap_atomic_idx_push();
-
-	idx = FIX_KMAP_BEGIN + type + KM_TYPE_NR * smp_processor_id();
-	vaddr = __fix_to_virt(idx);
-#ifdef CONFIG_DEBUG_HIGHMEM
-	/*
-	 * With debugging enabled, kunmap_atomic forces that entry to 0.
-	 * Make sure it was indeed properly unmapped.
-	 */
-	BUG_ON(!pte_none(get_fixmap_pte(vaddr)));
-#endif
-	/*
-	 * When debugging is off, kunmap_atomic leaves the previous mapping
-	 * in place, so the contained TLB flush ensures the TLB is updated
-	 * with the new mapping.
-	 */
-	set_fixmap_pte(idx, mk_pte(page, prot));
-
-	return (void *)vaddr;
-}
-EXPORT_SYMBOL(kmap_atomic_high_prot);
-
-void kunmap_atomic_high(void *kvaddr)
-{
-	unsigned long vaddr = (unsigned long) kvaddr & PAGE_MASK;
-	int idx, type;
-
-	if (kvaddr >= (void *)FIXADDR_START) {
-		type = kmap_atomic_idx();
-		idx = FIX_KMAP_BEGIN + type + KM_TYPE_NR * smp_processor_id();
-
-		if (cache_is_vivt())
-			__cpuc_flush_dcache_area((void *)vaddr, PAGE_SIZE);
-#ifdef CONFIG_DEBUG_HIGHMEM
-		BUG_ON(vaddr != __fix_to_virt(idx));
-		set_fixmap_pte(idx, __pte(0));
-#else
-		(void) idx;  /* to kill a warning */
-#endif
-		kmap_atomic_idx_pop();
-	} else if (vaddr >= PKMAP_ADDR(0) && vaddr < PKMAP_ADDR(LAST_PKMAP)) {
-		/* this address was obtained through kmap_high_get() */
-		kunmap_high(pte_page(pkmap_page_table[PKMAP_NR(vaddr)]));
-	}
-}
-EXPORT_SYMBOL(kunmap_atomic_high);
-
-void *kmap_atomic_pfn(unsigned long pfn)
-{
-	unsigned long vaddr;
-	int idx, type;
-	struct page *page = pfn_to_page(pfn);
-
-	preempt_disable();
-	pagefault_disable();
-	if (!PageHighMem(page))
-		return page_address(page);
-
-	type = kmap_atomic_idx_push();
-	idx = FIX_KMAP_BEGIN + type + KM_TYPE_NR * smp_processor_id();
-	vaddr = __fix_to_virt(idx);
-#ifdef CONFIG_DEBUG_HIGHMEM
-	BUG_ON(!pte_none(get_fixmap_pte(vaddr)));
-#endif
-	set_fixmap_pte(idx, pfn_pte(pfn, kmap_prot));
-
-	return (void *)vaddr;
-}


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[patch V2 07/18] csky/mm/highmem: Switch to generic kmap atomic

[Thomas Gleixner]

No reason having the same code in every architecture.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Guo Ren <guoren@kernel.org>
Cc: linux-csky@vger.kernel.org

---
 arch/csky/Kconfig               |    1 
 arch/csky/include/asm/highmem.h |    4 +-
 arch/csky/mm/highmem.c          |   75 ----------------------------------------
 3 files changed, 5 insertions(+), 75 deletions(-)

--- a/arch/csky/Kconfig
+++ b/arch/csky/Kconfig
@@ -286,6 +286,7 @@ config NR_CPUS
 config HIGHMEM
 	bool "High Memory Support"
 	depends on !CPU_CK610
+	select KMAP_LOCAL
 	default y
 
 config FORCE_MAX_ZONEORDER
--- a/arch/csky/include/asm/highmem.h
+++ b/arch/csky/include/asm/highmem.h
@@ -32,10 +32,12 @@ extern pte_t *pkmap_page_table;
 
 #define ARCH_HAS_KMAP_FLUSH_TLB
 extern void kmap_flush_tlb(unsigned long addr);
-extern void *kmap_atomic_pfn(unsigned long pfn);
 
 #define flush_cache_kmaps() do {} while (0)
 
+#define arch_kmap_local_post_map(vaddr, pteval)	kmap_flush_tlb(vaddr)
+#define arch_kmap_local_post_unmap(vaddr)	kmap_flush_tlb(vaddr)
+
 extern void kmap_init(void);
 
 #endif /* __KERNEL__ */
--- a/arch/csky/mm/highmem.c
+++ b/arch/csky/mm/highmem.c
@@ -9,8 +9,6 @@
 #include <asm/tlbflush.h>
 #include <asm/cacheflush.h>
 
-static pte_t *kmap_pte;
-
 unsigned long highstart_pfn, highend_pfn;
 
 void kmap_flush_tlb(unsigned long addr)
@@ -19,67 +17,7 @@ void kmap_flush_tlb(unsigned long addr)
 }
 EXPORT_SYMBOL(kmap_flush_tlb);
 
-void *kmap_atomic_high_prot(struct page *page, pgprot_t prot)
-{
-	unsigned long vaddr;
-	int idx, type;
-
-	type = kmap_atomic_idx_push();
-	idx = type + KM_TYPE_NR*smp_processor_id();
-	vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
-#ifdef CONFIG_DEBUG_HIGHMEM
-	BUG_ON(!pte_none(*(kmap_pte - idx)));
-#endif
-	set_pte(kmap_pte-idx, mk_pte(page, prot));
-	flush_tlb_one((unsigned long)vaddr);
-
-	return (void *)vaddr;
-}
-EXPORT_SYMBOL(kmap_atomic_high_prot);
-
-void kunmap_atomic_high(void *kvaddr)
-{
-	unsigned long vaddr = (unsigned long) kvaddr & PAGE_MASK;
-	int idx;
-
-	if (vaddr < FIXADDR_START)
-		return;
-
-#ifdef CONFIG_DEBUG_HIGHMEM
-	idx = KM_TYPE_NR*smp_processor_id() + kmap_atomic_idx();
-
-	BUG_ON(vaddr != __fix_to_virt(FIX_KMAP_BEGIN + idx));
-
-	pte_clear(&init_mm, vaddr, kmap_pte - idx);
-	flush_tlb_one(vaddr);
-#else
-	(void) idx; /* to kill a warning */
-#endif
-	kmap_atomic_idx_pop();
-}
-EXPORT_SYMBOL(kunmap_atomic_high);
-
-/*
- * This is the same as kmap_atomic() but can map memory that doesn't
- * have a struct page associated with it.
- */
-void *kmap_atomic_pfn(unsigned long pfn)
-{
-	unsigned long vaddr;
-	int idx, type;
-
-	pagefault_disable();
-
-	type = kmap_atomic_idx_push();
-	idx = type + KM_TYPE_NR*smp_processor_id();
-	vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
-	set_pte(kmap_pte-idx, pfn_pte(pfn, PAGE_KERNEL));
-	flush_tlb_one(vaddr);
-
-	return (void *) vaddr;
-}
-
-static void __init kmap_pages_init(void)
+void __init kmap_init(void)
 {
 	unsigned long vaddr;
 	pgd_t *pgd;
@@ -96,14 +34,3 @@ static void __init kmap_pages_init(void)
 	pte = pte_offset_kernel(pmd, vaddr);
 	pkmap_page_table = pte;
 }
-
-void __init kmap_init(void)
-{
-	unsigned long vaddr;
-
-	kmap_pages_init();
-
-	vaddr = __fix_to_virt(FIX_KMAP_BEGIN);
-
-	kmap_pte = pte_offset_kernel((pmd_t *)pgd_offset_k(vaddr), vaddr);
-}


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[patch V2 08/18] microblaze/mm/highmem: Switch to generic kmap atomic

[Thomas Gleixner]

No reason having the same code in every architecture.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Michal Simek <monstr@monstr.eu>

diff --git a/arch/microblaze/Kconfig b/arch/microblaze/Kconfig
index d262ac0c8714..186a0526564c 100644
--- a/arch/microblaze/Kconfig
+++ b/arch/microblaze/Kconfig
@@ -170,6 +170,7 @@ config XILINX_UNCACHED_SHADOW
 config HIGHMEM
 	bool "High memory support"
 	depends on MMU
+	select KMAP_LOCAL
 	help
 	  The address space of Microblaze processors is only 4 Gigabytes large
 	  and it has to accommodate user address space, kernel address
diff --git a/arch/microblaze/include/asm/highmem.h b/arch/microblaze/include/asm/highmem.h
index 284ca8fb54c1..4418633fb163 100644
--- a/arch/microblaze/include/asm/highmem.h
+++ b/arch/microblaze/include/asm/highmem.h
@@ -25,7 +25,6 @@
 #include <linux/uaccess.h>
 #include <asm/fixmap.h>
 
-extern pte_t *kmap_pte;
 extern pte_t *pkmap_page_table;
 
 /*
@@ -52,6 +51,11 @@ extern pte_t *pkmap_page_table;
 
 #define flush_cache_kmaps()	{ flush_icache(); flush_dcache(); }
 
+#define arch_kmap_local_post_map(vaddr, pteval)	\
+	local_flush_tlb_page(NULL, vaddr);
+#define arch_kmap_local_post_unmap(vaddr)	\
+	local_flush_tlb_page(NULL, vaddr);
+
 #endif /* __KERNEL__ */
 
 #endif /* _ASM_HIGHMEM_H */
diff --git a/arch/microblaze/mm/Makefile b/arch/microblaze/mm/Makefile
index 1b16875cea70..8ced71100047 100644
--- a/arch/microblaze/mm/Makefile
+++ b/arch/microblaze/mm/Makefile
@@ -6,4 +6,3 @@
 obj-y := consistent.o init.o
 
 obj-$(CONFIG_MMU) += pgtable.o mmu_context.o fault.o
-obj-$(CONFIG_HIGHMEM) += highmem.o
diff --git a/arch/microblaze/mm/highmem.c b/arch/microblaze/mm/highmem.c
deleted file mode 100644
index 92e0890416c9..000000000000
--- a/arch/microblaze/mm/highmem.c
+++ /dev/null
@@ -1,78 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0
-/*
- * highmem.c: virtual kernel memory mappings for high memory
- *
- * PowerPC version, stolen from the i386 version.
- *
- * Used in CONFIG_HIGHMEM systems for memory pages which
- * are not addressable by direct kernel virtual addresses.
- *
- * Copyright (C) 1999 Gerhard Wichert, Siemens AG
- *		      Gerhard.Wichert@pdb.siemens.de
- *
- *
- * Redesigned the x86 32-bit VM architecture to deal with
- * up to 16 Terrabyte physical memory. With current x86 CPUs
- * we now support up to 64 Gigabytes physical RAM.
- *
- * Copyright (C) 1999 Ingo Molnar <mingo@redhat.com>
- *
- * Reworked for PowerPC by various contributors. Moved from
- * highmem.h by Benjamin Herrenschmidt (c) 2009 IBM Corp.
- */
-
-#include <linux/export.h>
-#include <linux/highmem.h>
-
-/*
- * The use of kmap_atomic/kunmap_atomic is discouraged - kmap/kunmap
- * gives a more generic (and caching) interface. But kmap_atomic can
- * be used in IRQ contexts, so in some (very limited) cases we need
- * it.
- */
-#include <asm/tlbflush.h>
-
-void *kmap_atomic_high_prot(struct page *page, pgprot_t prot)
-{
-
-	unsigned long vaddr;
-	int idx, type;
-
-	type = kmap_atomic_idx_push();
-	idx = type + KM_TYPE_NR*smp_processor_id();
-	vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
-#ifdef CONFIG_DEBUG_HIGHMEM
-	BUG_ON(!pte_none(*(kmap_pte-idx)));
-#endif
-	set_pte_at(&init_mm, vaddr, kmap_pte-idx, mk_pte(page, prot));
-	local_flush_tlb_page(NULL, vaddr);
-
-	return (void *) vaddr;
-}
-EXPORT_SYMBOL(kmap_atomic_high_prot);
-
-void kunmap_atomic_high(void *kvaddr)
-{
-	unsigned long vaddr = (unsigned long) kvaddr & PAGE_MASK;
-	int type;
-	unsigned int idx;
-
-	if (vaddr < __fix_to_virt(FIX_KMAP_END))
-		return;
-
-	type = kmap_atomic_idx();
-
-	idx = type + KM_TYPE_NR * smp_processor_id();
-#ifdef CONFIG_DEBUG_HIGHMEM
-	BUG_ON(vaddr != __fix_to_virt(FIX_KMAP_BEGIN + idx));
-#endif
-	/*
-	 * force other mappings to Oops if they'll try to access
-	 * this pte without first remap it
-	 */
-	pte_clear(&init_mm, vaddr, kmap_pte-idx);
-	local_flush_tlb_page(NULL, vaddr);
-
-	kmap_atomic_idx_pop();
-}
-EXPORT_SYMBOL(kunmap_atomic_high);
diff --git a/arch/microblaze/mm/init.c b/arch/microblaze/mm/init.c
index 3344d4a1fe89..3f4e41787a4e 100644
--- a/arch/microblaze/mm/init.c
+++ b/arch/microblaze/mm/init.c
@@ -49,17 +49,11 @@ unsigned long lowmem_size;
 EXPORT_SYMBOL(min_low_pfn);
 EXPORT_SYMBOL(max_low_pfn);
 
-#ifdef CONFIG_HIGHMEM
-pte_t *kmap_pte;
-EXPORT_SYMBOL(kmap_pte);
-
 static void __init highmem_init(void)
 {
 	pr_debug("%x\n", (u32)PKMAP_BASE);
 	map_page(PKMAP_BASE, 0, 0);	/* XXX gross */
 	pkmap_page_table = virt_to_kpte(PKMAP_BASE);
-
-	kmap_pte = virt_to_kpte(__fix_to_virt(FIX_KMAP_BEGIN));
 }
 
 static void highmem_setup(void)


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[patch V2 09/18] mips/mm/highmem: Switch to generic kmap atomic

[Thomas Gleixner]

No reason having the same code in every architecture

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: linux-mips@vger.kernel.org

diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index 8f328298f8cc..ed6b3de944a8 100644
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -2654,6 +2654,7 @@ config MIPS_CRC_SUPPORT
 config HIGHMEM
 	bool "High Memory Support"
 	depends on 32BIT && CPU_SUPPORTS_HIGHMEM && SYS_SUPPORTS_HIGHMEM && !CPU_MIPS32_3_5_EVA
+	select KMAP_LOCAL
 
 config CPU_SUPPORTS_HIGHMEM
 	bool
diff --git a/arch/mips/include/asm/highmem.h b/arch/mips/include/asm/highmem.h
index f1f788b57166..cb2e0fb8483b 100644
--- a/arch/mips/include/asm/highmem.h
+++ b/arch/mips/include/asm/highmem.h
@@ -48,11 +48,11 @@ extern pte_t *pkmap_page_table;
 
 #define ARCH_HAS_KMAP_FLUSH_TLB
 extern void kmap_flush_tlb(unsigned long addr);
-extern void *kmap_atomic_pfn(unsigned long pfn);
 
 #define flush_cache_kmaps()	BUG_ON(cpu_has_dc_aliases)
 
-extern void kmap_init(void);
+#define arch_kmap_local_post_map(vaddr, pteval)	local_flush_tlb_one(vaddr)
+#define arch_kmap_local_post_unmap(vaddr)	local_flush_tlb_one(vaddr)
 
 #endif /* __KERNEL__ */
 
diff --git a/arch/mips/mm/highmem.c b/arch/mips/mm/highmem.c
index 5fec7f45d79a..57e2f08f00d0 100644
--- a/arch/mips/mm/highmem.c
+++ b/arch/mips/mm/highmem.c
@@ -8,8 +8,6 @@
 #include <asm/fixmap.h>
 #include <asm/tlbflush.h>
 
-static pte_t *kmap_pte;
-
 unsigned long highstart_pfn, highend_pfn;
 
 void kmap_flush_tlb(unsigned long addr)
@@ -17,78 +15,3 @@ void kmap_flush_tlb(unsigned long addr)
 	flush_tlb_one(addr);
 }
 EXPORT_SYMBOL(kmap_flush_tlb);
-
-void *kmap_atomic_high_prot(struct page *page, pgprot_t prot)
-{
-	unsigned long vaddr;
-	int idx, type;
-
-	type = kmap_atomic_idx_push();
-	idx = type + KM_TYPE_NR*smp_processor_id();
-	vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
-#ifdef CONFIG_DEBUG_HIGHMEM
-	BUG_ON(!pte_none(*(kmap_pte - idx)));
-#endif
-	set_pte(kmap_pte-idx, mk_pte(page, prot));
-	local_flush_tlb_one((unsigned long)vaddr);
-
-	return (void*) vaddr;
-}
-EXPORT_SYMBOL(kmap_atomic_high_prot);
-
-void kunmap_atomic_high(void *kvaddr)
-{
-	unsigned long vaddr = (unsigned long) kvaddr & PAGE_MASK;
-	int type __maybe_unused;
-
-	if (vaddr < FIXADDR_START)
-		return;
-
-	type = kmap_atomic_idx();
-#ifdef CONFIG_DEBUG_HIGHMEM
-	{
-		int idx = type + KM_TYPE_NR * smp_processor_id();
-
-		BUG_ON(vaddr != __fix_to_virt(FIX_KMAP_BEGIN + idx));
-
-		/*
-		 * force other mappings to Oops if they'll try to access
-		 * this pte without first remap it
-		 */
-		pte_clear(&init_mm, vaddr, kmap_pte-idx);
-		local_flush_tlb_one(vaddr);
-	}
-#endif
-	kmap_atomic_idx_pop();
-}
-EXPORT_SYMBOL(kunmap_atomic_high);
-
-/*
- * This is the same as kmap_atomic() but can map memory that doesn't
- * have a struct page associated with it.
- */
-void *kmap_atomic_pfn(unsigned long pfn)
-{
-	unsigned long vaddr;
-	int idx, type;
-
-	preempt_disable();
-	pagefault_disable();
-
-	type = kmap_atomic_idx_push();
-	idx = type + KM_TYPE_NR*smp_processor_id();
-	vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
-	set_pte(kmap_pte-idx, pfn_pte(pfn, PAGE_KERNEL));
-	flush_tlb_one(vaddr);
-
-	return (void*) vaddr;
-}
-
-void __init kmap_init(void)
-{
-	unsigned long kmap_vstart;
-
-	/* cache the first kmap pte */
-	kmap_vstart = __fix_to_virt(FIX_KMAP_BEGIN);
-	kmap_pte = virt_to_kpte(kmap_vstart);
-}
diff --git a/arch/mips/mm/init.c b/arch/mips/mm/init.c
index 6c7bbfe35ba3..e5de8e9c2ede 100644
--- a/arch/mips/mm/init.c
+++ b/arch/mips/mm/init.c
@@ -402,9 +402,6 @@ void __init paging_init(void)
 
 	pagetable_init();
 
-#ifdef CONFIG_HIGHMEM
-	kmap_init();
-#endif
 #ifdef CONFIG_ZONE_DMA
 	max_zone_pfns[ZONE_DMA] = MAX_DMA_PFN;
 #endif


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[patch V2 10/18] nds32/mm/highmem: Switch to generic kmap atomic

[Thomas Gleixner]

The mapping code is odd and looks broken. See FIXME in the comment.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Nick Hu <nickhu@andestech.com>
Cc: Greentime Hu <green.hu@gmail.com>
Cc: Vincent Chen <deanbo422@gmail.com>

diff --git a/arch/nds32/Kconfig.cpu b/arch/nds32/Kconfig.cpu
index f88a12fdf0f3..c7add11ea36e 100644
--- a/arch/nds32/Kconfig.cpu
+++ b/arch/nds32/Kconfig.cpu
@@ -157,6 +157,7 @@ config HW_SUPPORT_UNALIGNMENT_ACCESS
 config HIGHMEM
 	bool "High Memory Support"
 	depends on MMU && !CPU_CACHE_ALIASING
+        select KMAP_LOCAL
 	help
 	  The address space of Andes processors is only 4 Gigabytes large
 	  and it has to accommodate user address space, kernel address
diff --git a/arch/nds32/include/asm/highmem.h b/arch/nds32/include/asm/highmem.h
index fe986d0e6e3f..d844c282c090 100644
--- a/arch/nds32/include/asm/highmem.h
+++ b/arch/nds32/include/asm/highmem.h
@@ -45,11 +45,22 @@ extern pte_t *pkmap_page_table;
 extern void kmap_init(void);
 
 /*
- * The following functions are already defined by <linux/highmem.h>
- * when CONFIG_HIGHMEM is not set.
+ * FIXME: The below looks broken vs. a kmap_atomic() in task context which
+ * is interupted and another kmap_atomic() happens in interrupt context.
+ * But what do I know about nds32. -- tglx
  */
-#ifdef CONFIG_HIGHMEM
-extern void *kmap_atomic_pfn(unsigned long pfn);
-#endif
+#define arch_kmap_local_post_map(vaddr, pteval)			\
+	do {							\
+		__nds32__tlbop_inv(vaddr);			\
+		__nds32__mtsr_dsb(vaddr, NDS32_SR_TLB_VPN);	\
+		__nds32__tlbop_rwr(pteval);			\
+		__nds32__isb();					\
+	} while (0)
+
+#define arch_kmap_local_pre_unmap(vaddr, pte)			\
+	do {							\
+		__nds32__tlbop_inv(vaddr);			\
+		__nds32__isb();					\
+	} while (0)
 
 #endif
diff --git a/arch/nds32/mm/Makefile b/arch/nds32/mm/Makefile
index 897ecaf5cf54..14fb2e8eb036 100644
--- a/arch/nds32/mm/Makefile
+++ b/arch/nds32/mm/Makefile
@@ -3,7 +3,6 @@ obj-y				:= extable.o tlb.o fault.o init.o mmap.o \
                                    mm-nds32.o cacheflush.o proc.o
 
 obj-$(CONFIG_ALIGNMENT_TRAP)	+= alignment.o
-obj-$(CONFIG_HIGHMEM)           += highmem.o
 
 ifdef CONFIG_FUNCTION_TRACER
 CFLAGS_REMOVE_proc.o     = $(CC_FLAGS_FTRACE)
diff --git a/arch/nds32/mm/highmem.c b/arch/nds32/mm/highmem.c
deleted file mode 100644
index 4284cd59e21a..000000000000
--- a/arch/nds32/mm/highmem.c
+++ /dev/null
@@ -1,48 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0
-// Copyright (C) 2005-2017 Andes Technology Corporation
-
-#include <linux/export.h>
-#include <linux/highmem.h>
-#include <linux/sched.h>
-#include <linux/smp.h>
-#include <linux/interrupt.h>
-#include <linux/memblock.h>
-#include <asm/fixmap.h>
-#include <asm/tlbflush.h>
-
-void *kmap_atomic_high_prot(struct page *page, pgprot_t prot)
-{
-	unsigned int idx;
-	unsigned long vaddr, pte;
-	int type;
-	pte_t *ptep;
-
-	type = kmap_atomic_idx_push();
-
-	idx = type + KM_TYPE_NR * smp_processor_id();
-	vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
-	pte = (page_to_pfn(page) << PAGE_SHIFT) | prot;
-	ptep = pte_offset_kernel(pmd_off_k(vaddr), vaddr);
-	set_pte(ptep, pte);
-
-	__nds32__tlbop_inv(vaddr);
-	__nds32__mtsr_dsb(vaddr, NDS32_SR_TLB_VPN);
-	__nds32__tlbop_rwr(pte);
-	__nds32__isb();
-	return (void *)vaddr;
-}
-EXPORT_SYMBOL(kmap_atomic_high_prot);
-
-void kunmap_atomic_high(void *kvaddr)
-{
-	if (kvaddr >= (void *)FIXADDR_START) {
-		unsigned long vaddr = (unsigned long)kvaddr;
-		pte_t *ptep;
-		kmap_atomic_idx_pop();
-		__nds32__tlbop_inv(vaddr);
-		__nds32__isb();
-		ptep = pte_offset_kernel(pmd_off_k(vaddr), vaddr);
-		set_pte(ptep, 0);
-	}
-}
-EXPORT_SYMBOL(kunmap_atomic_high);


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[patch V2 11/18] powerpc/mm/highmem: Switch to generic kmap atomic

[Thomas Gleixner]

No reason having the same code in every architecture

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: linuxppc-dev@lists.ozlabs.org
---
 arch/powerpc/Kconfig               |    1 
 arch/powerpc/include/asm/highmem.h |    6 ++-
 arch/powerpc/mm/Makefile           |    1 
 arch/powerpc/mm/highmem.c          |   67 -------------------------------------
 arch/powerpc/mm/mem.c              |    7 ---
 5 files changed, 6 insertions(+), 76 deletions(-)

--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -409,6 +409,7 @@ menu "Kernel options"
 config HIGHMEM
 	bool "High memory support"
 	depends on PPC32
+        select KMAP_LOCAL
 
 source "kernel/Kconfig.hz"
 
--- a/arch/powerpc/include/asm/highmem.h
+++ b/arch/powerpc/include/asm/highmem.h
@@ -29,7 +29,6 @@
 #include <asm/page.h>
 #include <asm/fixmap.h>
 
-extern pte_t *kmap_pte;
 extern pte_t *pkmap_page_table;
 
 /*
@@ -60,6 +59,11 @@ extern pte_t *pkmap_page_table;
 
 #define flush_cache_kmaps()	flush_cache_all()
 
+#define arch_kmap_local_post_map(vaddr, pteval)	\
+	local_flush_tlb_page(NULL, vaddr)
+#define arch_kmap_local_post_unmap(vaddr)	\
+	local_flush_tlb_page(NULL, vaddr)
+
 #endif /* __KERNEL__ */
 
 #endif /* _ASM_HIGHMEM_H */
--- a/arch/powerpc/mm/Makefile
+++ b/arch/powerpc/mm/Makefile
@@ -16,7 +16,6 @@ obj-$(CONFIG_NEED_MULTIPLE_NODES) += num
 obj-$(CONFIG_PPC_MM_SLICES)	+= slice.o
 obj-$(CONFIG_HUGETLB_PAGE)	+= hugetlbpage.o
 obj-$(CONFIG_NOT_COHERENT_CACHE) += dma-noncoherent.o
-obj-$(CONFIG_HIGHMEM)		+= highmem.o
 obj-$(CONFIG_PPC_COPRO_BASE)	+= copro_fault.o
 obj-$(CONFIG_PPC_PTDUMP)	+= ptdump/
 obj-$(CONFIG_KASAN)		+= kasan/
--- a/arch/powerpc/mm/highmem.c
+++ /dev/null
@@ -1,67 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0
-/*
- * highmem.c: virtual kernel memory mappings for high memory
- *
- * PowerPC version, stolen from the i386 version.
- *
- * Used in CONFIG_HIGHMEM systems for memory pages which
- * are not addressable by direct kernel virtual addresses.
- *
- * Copyright (C) 1999 Gerhard Wichert, Siemens AG
- *		      Gerhard.Wichert@pdb.siemens.de
- *
- *
- * Redesigned the x86 32-bit VM architecture to deal with
- * up to 16 Terrabyte physical memory. With current x86 CPUs
- * we now support up to 64 Gigabytes physical RAM.
- *
- * Copyright (C) 1999 Ingo Molnar <mingo@redhat.com>
- *
- * Reworked for PowerPC by various contributors. Moved from
- * highmem.h by Benjamin Herrenschmidt (c) 2009 IBM Corp.
- */
-
-#include <linux/highmem.h>
-#include <linux/module.h>
-
-void *kmap_atomic_high_prot(struct page *page, pgprot_t prot)
-{
-	unsigned long vaddr;
-	int idx, type;
-
-	type = kmap_atomic_idx_push();
-	idx = type + KM_TYPE_NR*smp_processor_id();
-	vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
-	WARN_ON(IS_ENABLED(CONFIG_DEBUG_HIGHMEM) && !pte_none(*(kmap_pte - idx)));
-	__set_pte_at(&init_mm, vaddr, kmap_pte-idx, mk_pte(page, prot), 1);
-	local_flush_tlb_page(NULL, vaddr);
-
-	return (void*) vaddr;
-}
-EXPORT_SYMBOL(kmap_atomic_high_prot);
-
-void kunmap_atomic_high(void *kvaddr)
-{
-	unsigned long vaddr = (unsigned long) kvaddr & PAGE_MASK;
-
-	if (vaddr < __fix_to_virt(FIX_KMAP_END))
-		return;
-
-	if (IS_ENABLED(CONFIG_DEBUG_HIGHMEM)) {
-		int type = kmap_atomic_idx();
-		unsigned int idx;
-
-		idx = type + KM_TYPE_NR * smp_processor_id();
-		WARN_ON(vaddr != __fix_to_virt(FIX_KMAP_BEGIN + idx));
-
-		/*
-		 * force other mappings to Oops if they'll try to access
-		 * this pte without first remap it
-		 */
-		pte_clear(&init_mm, vaddr, kmap_pte-idx);
-		local_flush_tlb_page(NULL, vaddr);
-	}
-
-	kmap_atomic_idx_pop();
-}
-EXPORT_SYMBOL(kunmap_atomic_high);
--- a/arch/powerpc/mm/mem.c
+++ b/arch/powerpc/mm/mem.c
@@ -61,11 +61,6 @@
 unsigned long long memory_limit;
 bool init_mem_is_free;
 
-#ifdef CONFIG_HIGHMEM
-pte_t *kmap_pte;
-EXPORT_SYMBOL(kmap_pte);
-#endif
-
 pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
 			      unsigned long size, pgprot_t vma_prot)
 {
@@ -235,8 +230,6 @@ void __init paging_init(void)
 
 	map_kernel_page(PKMAP_BASE, 0, __pgprot(0));	/* XXX gross */
 	pkmap_page_table = virt_to_kpte(PKMAP_BASE);
-
-	kmap_pte = virt_to_kpte(__fix_to_virt(FIX_KMAP_BEGIN));
 #endif /* CONFIG_HIGHMEM */
 
 	printk(KERN_DEBUG "Top of RAM: 0x%llx, Total RAM: 0x%llx\n",


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[patch V2 12/18] sparc/mm/highmem: Switch to generic kmap atomic

[Thomas Gleixner]

No reason having the same code in every architecture

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: sparclinux@vger.kernel.org

---
 arch/sparc/Kconfig               |    1 
 arch/sparc/include/asm/highmem.h |    7 +-
 arch/sparc/mm/Makefile           |    3 -
 arch/sparc/mm/highmem.c          |  115 ---------------------------------------
 arch/sparc/mm/srmmu.c            |    2 
 5 files changed, 6 insertions(+), 122 deletions(-)

--- a/arch/sparc/Kconfig
+++ b/arch/sparc/Kconfig
@@ -139,6 +139,7 @@ config MMU
 config HIGHMEM
 	bool
 	default y if SPARC32
+        select KMAP_LOCAL
 
 config ZONE_DMA
 	bool
--- a/arch/sparc/include/asm/highmem.h
+++ b/arch/sparc/include/asm/highmem.h
@@ -33,8 +33,6 @@ extern unsigned long highstart_pfn, high
 #define kmap_prot __pgprot(SRMMU_ET_PTE | SRMMU_PRIV | SRMMU_CACHE)
 extern pte_t *pkmap_page_table;
 
-void kmap_init(void) __init;
-
 /*
  * Right now we initialize only a single pte table. It can be extended
  * easily, subsequent pte tables have to be allocated in one physical
@@ -53,6 +51,11 @@ void kmap_init(void) __init;
 
 #define flush_cache_kmaps()	flush_cache_all()
 
+/* FIXME: Use __flush_tlb_one(vaddr) instead of flush_cache_all() -- Anton */
+#define arch_kmap_local_post_map(vaddr, pteval)	flush_cache_all()
+#define arch_kmap_local_post_unmap(vaddr)	flush_cache_all()
+
+
 #endif /* __KERNEL__ */
 
 #endif /* _ASM_HIGHMEM_H */
--- a/arch/sparc/mm/Makefile
+++ b/arch/sparc/mm/Makefile
@@ -15,6 +15,3 @@ obj-$(CONFIG_SPARC32)   += leon_mm.o
 
 # Only used by sparc64
 obj-$(CONFIG_HUGETLB_PAGE) += hugetlbpage.o
-
-# Only used by sparc32
-obj-$(CONFIG_HIGHMEM)   += highmem.o
--- a/arch/sparc/mm/highmem.c
+++ /dev/null
@@ -1,115 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0
-/*
- *  highmem.c: virtual kernel memory mappings for high memory
- *
- *  Provides kernel-static versions of atomic kmap functions originally
- *  found as inlines in include/asm-sparc/highmem.h.  These became
- *  needed as kmap_atomic() and kunmap_atomic() started getting
- *  called from within modules.
- *  -- Tomas Szepe <szepe@pinerecords.com>, September 2002
- *
- *  But kmap_atomic() and kunmap_atomic() cannot be inlined in
- *  modules because they are loaded with btfixup-ped functions.
- */
-
-/*
- * The use of kmap_atomic/kunmap_atomic is discouraged - kmap/kunmap
- * gives a more generic (and caching) interface. But kmap_atomic can
- * be used in IRQ contexts, so in some (very limited) cases we need it.
- *
- * XXX This is an old text. Actually, it's good to use atomic kmaps,
- * provided you remember that they are atomic and not try to sleep
- * with a kmap taken, much like a spinlock. Non-atomic kmaps are
- * shared by CPUs, and so precious, and establishing them requires IPI.
- * Atomic kmaps are lightweight and we may have NCPUS more of them.
- */
-#include <linux/highmem.h>
-#include <linux/export.h>
-#include <linux/mm.h>
-
-#include <asm/cacheflush.h>
-#include <asm/tlbflush.h>
-#include <asm/vaddrs.h>
-
-static pte_t *kmap_pte;
-
-void __init kmap_init(void)
-{
-	unsigned long address = __fix_to_virt(FIX_KMAP_BEGIN);
-
-        /* cache the first kmap pte */
-        kmap_pte = virt_to_kpte(address);
-}
-
-void *kmap_atomic_high_prot(struct page *page, pgprot_t prot)
-{
-	unsigned long vaddr;
-	long idx, type;
-
-	type = kmap_atomic_idx_push();
-	idx = type + KM_TYPE_NR*smp_processor_id();
-	vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
-
-/* XXX Fix - Anton */
-#if 0
-	__flush_cache_one(vaddr);
-#else
-	flush_cache_all();
-#endif
-
-#ifdef CONFIG_DEBUG_HIGHMEM
-	BUG_ON(!pte_none(*(kmap_pte-idx)));
-#endif
-	set_pte(kmap_pte-idx, mk_pte(page, prot));
-/* XXX Fix - Anton */
-#if 0
-	__flush_tlb_one(vaddr);
-#else
-	flush_tlb_all();
-#endif
-
-	return (void*) vaddr;
-}
-EXPORT_SYMBOL(kmap_atomic_high_prot);
-
-void kunmap_atomic_high(void *kvaddr)
-{
-	unsigned long vaddr = (unsigned long) kvaddr & PAGE_MASK;
-	int type;
-
-	if (vaddr < FIXADDR_START)
-		return;
-
-	type = kmap_atomic_idx();
-
-#ifdef CONFIG_DEBUG_HIGHMEM
-	{
-		unsigned long idx;
-
-		idx = type + KM_TYPE_NR * smp_processor_id();
-		BUG_ON(vaddr != __fix_to_virt(FIX_KMAP_BEGIN+idx));
-
-		/* XXX Fix - Anton */
-#if 0
-		__flush_cache_one(vaddr);
-#else
-		flush_cache_all();
-#endif
-
-		/*
-		 * force other mappings to Oops if they'll try to access
-		 * this pte without first remap it
-		 */
-		pte_clear(&init_mm, vaddr, kmap_pte-idx);
-		/* XXX Fix - Anton */
-#if 0
-		__flush_tlb_one(vaddr);
-#else
-		flush_tlb_all();
-#endif
-	}
-#endif
-
-	kmap_atomic_idx_pop();
-}
-EXPORT_SYMBOL(kunmap_atomic_high);
--- a/arch/sparc/mm/srmmu.c
+++ b/arch/sparc/mm/srmmu.c
@@ -971,8 +971,6 @@ void __init srmmu_paging_init(void)
 
 	sparc_context_init(num_contexts);
 
-	kmap_init();
-
 	{
 		unsigned long max_zone_pfn[MAX_NR_ZONES] = { 0 };
 


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[patch V2 13/18] xtensa/mm/highmem: Switch to generic kmap atomic

[Thomas Gleixner]

No reason having the same code in every architecture

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Chris Zankel <chris@zankel.net>
Cc: Max Filippov <jcmvbkbc@gmail.com>
Cc: linux-xtensa@linux-xtensa.org

---
 arch/xtensa/Kconfig               |    1 
 arch/xtensa/include/asm/highmem.h |    9 +++++++
 arch/xtensa/mm/highmem.c          |   44 +++-----------------------------------
 3 files changed, 14 insertions(+), 40 deletions(-)

--- a/arch/xtensa/Kconfig
+++ b/arch/xtensa/Kconfig
@@ -666,6 +666,7 @@ endchoice
 config HIGHMEM
 	bool "High Memory Support"
 	depends on MMU
+        select KMAP_LOCAL
 	help
 	  Linux can use the full amount of RAM in the system by
 	  default. However, the default MMUv2 setup only maps the
--- a/arch/xtensa/include/asm/highmem.h
+++ b/arch/xtensa/include/asm/highmem.h
@@ -68,6 +68,15 @@ static inline void flush_cache_kmaps(voi
 	flush_cache_all();
 }
 
+enum fixed_addresses kmap_local_map_idx(int type, unsigned long pfn);
+#define arch_kmap_local_map_idx		kmap_local_map_idx
+
+enum fixed_addresses kmap_local_unmap_idx(int type, unsigned long addr);
+#define arch_kmap_local_unmap_idx	kmap_local_unmap_idx
+
+#define arch_kmap_local_post_unmap(vaddr)	\
+	local_flush_tlb_kernel_range(vaddr, vaddr + PAGE_SIZE)
+
 void kmap_init(void);
 
 #endif
--- a/arch/xtensa/mm/highmem.c
+++ b/arch/xtensa/mm/highmem.c
@@ -12,8 +12,6 @@
 #include <linux/highmem.h>
 #include <asm/tlbflush.h>
 
-static pte_t *kmap_pte;
-
 #if DCACHE_WAY_SIZE > PAGE_SIZE
 unsigned int last_pkmap_nr_arr[DCACHE_N_COLORS];
 wait_queue_head_t pkmap_map_wait_arr[DCACHE_N_COLORS];
@@ -37,55 +35,21 @@ static inline enum fixed_addresses kmap_
 		color;
 }
 
-void *kmap_atomic_high_prot(struct page *page, pgprot_t prot)
+enum fixed_addresses kmap_local_map_idx(int type, unsigned long pfn)
 {
-	enum fixed_addresses idx;
-	unsigned long vaddr;
-
-	idx = kmap_idx(kmap_atomic_idx_push(),
-		       DCACHE_ALIAS(page_to_phys(page)));
-	vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
-#ifdef CONFIG_DEBUG_HIGHMEM
-	BUG_ON(!pte_none(*(kmap_pte + idx)));
-#endif
-	set_pte(kmap_pte + idx, mk_pte(page, prot));
-
-	return (void *)vaddr;
+	return kmap_idx(type, DCACHE_ALIAS(pfn << PAGE_SHIFT);
 }
-EXPORT_SYMBOL(kmap_atomic_high_prot);
 
-void kunmap_atomic_high(void *kvaddr)
+enum fixed_addresses kmap_local_unmap_idx(int type, unsigned long addr)
 {
-	if (kvaddr >= (void *)FIXADDR_START &&
-	    kvaddr < (void *)FIXADDR_TOP) {
-		int idx = kmap_idx(kmap_atomic_idx(),
-				   DCACHE_ALIAS((unsigned long)kvaddr));
-
-		/*
-		 * Force other mappings to Oops if they'll try to access this
-		 * pte without first remap it.  Keeping stale mappings around
-		 * is a bad idea also, in case the page changes cacheability
-		 * attributes or becomes a protected page in a hypervisor.
-		 */
-		pte_clear(&init_mm, kvaddr, kmap_pte + idx);
-		local_flush_tlb_kernel_range((unsigned long)kvaddr,
-					     (unsigned long)kvaddr + PAGE_SIZE);
-
-		kmap_atomic_idx_pop();
-	}
+	return kmap_idx(type, DCACHE_ALIAS(addr));
 }
-EXPORT_SYMBOL(kunmap_atomic_high);
 
 void __init kmap_init(void)
 {
-	unsigned long kmap_vstart;
-
 	/* Check if this memory layout is broken because PKMAP overlaps
 	 * page table.
 	 */
 	BUILD_BUG_ON(PKMAP_BASE < TLBTEMP_BASE_1 + TLBTEMP_SIZE);
-	/* cache the first kmap pte */
-	kmap_vstart = __fix_to_virt(FIX_KMAP_BEGIN);
-	kmap_pte = virt_to_kpte(kmap_vstart);
 	kmap_waitqueues_init();
 }


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[patch V2 14/18] mm/highmem: Remove the old kmap_atomic cruft

[Thomas Gleixner]

All users gone.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

---
 include/linux/highmem.h |   61 ++----------------------------------------------
 mm/highmem.c            |   28 ++++++++++++++++++----
 2 files changed, 27 insertions(+), 62 deletions(-)

--- a/include/linux/highmem.h
+++ b/include/linux/highmem.h
@@ -88,31 +88,16 @@ static inline void kunmap(struct page *p
  * be used in IRQ contexts, so in some (very limited) cases we need
  * it.
  */
-
-#ifndef CONFIG_KMAP_LOCAL
-void *kmap_atomic_high_prot(struct page *page, pgprot_t prot);
-void kunmap_atomic_high(void *kvaddr);
-
 static inline void *kmap_atomic_prot(struct page *page, pgprot_t prot)
 {
 	preempt_disable();
 	pagefault_disable();
-	if (!PageHighMem(page))
-		return page_address(page);
-	return kmap_atomic_high_prot(page, prot);
-}
-
-static inline void __kunmap_atomic(void *vaddr)
-{
-	kunmap_atomic_high(vaddr);
+	return __kmap_local_page_prot(page, prot);
 }
-#else /* !CONFIG_KMAP_LOCAL */
 
-static inline void *kmap_atomic_prot(struct page *page, pgprot_t prot)
+static inline void *kmap_atomic(struct page *page)
 {
-	preempt_disable();
-	pagefault_disable();
-	return __kmap_local_page_prot(page, prot);
+	return kmap_atomic_prot(page, kmap_prot);
 }
 
 static inline void *kmap_atomic_pfn(unsigned long pfn)
@@ -127,13 +112,6 @@ static inline void __kunmap_atomic(void
 	kunmap_local_indexed(addr);
 }
 
-#endif /* CONFIG_KMAP_LOCAL */
-
-static inline void *kmap_atomic(struct page *page)
-{
-	return kmap_atomic_prot(page, kmap_prot);
-}
-
 /* declarations for linux/mm/highmem.c */
 unsigned int nr_free_highpages(void);
 extern atomic_long_t _totalhigh_pages;
@@ -226,39 +204,6 @@ static inline void __kunmap_atomic(void
 
 #endif /* CONFIG_HIGHMEM */
 
-#if defined(CONFIG_HIGHMEM) || defined(CONFIG_X86_32)
-
-DECLARE_PER_CPU(int, __kmap_atomic_idx);
-
-static inline int kmap_atomic_idx_push(void)
-{
-	int idx = __this_cpu_inc_return(__kmap_atomic_idx) - 1;
-
-#ifdef CONFIG_DEBUG_HIGHMEM
-	WARN_ON_ONCE(in_irq() && !irqs_disabled());
-	BUG_ON(idx >= KM_TYPE_NR);
-#endif
-	return idx;
-}
-
-static inline int kmap_atomic_idx(void)
-{
-	return __this_cpu_read(__kmap_atomic_idx) - 1;
-}
-
-static inline void kmap_atomic_idx_pop(void)
-{
-#ifdef CONFIG_DEBUG_HIGHMEM
-	int idx = __this_cpu_dec_return(__kmap_atomic_idx);
-
-	BUG_ON(idx < 0);
-#else
-	__this_cpu_dec(__kmap_atomic_idx);
-#endif
-}
-
-#endif
-
 /*
  * Prevent people trying to call kunmap_atomic() as if it were kunmap()
  * kunmap_atomic() should get the return value of kmap_atomic, not the page.
--- a/mm/highmem.c
+++ b/mm/highmem.c
@@ -32,10 +32,6 @@
 #include <linux/vmalloc.h>
 #include <asm/fixmap.h>
 
-#if defined(CONFIG_HIGHMEM) || defined(CONFIG_X86_32)
-DEFINE_PER_CPU(int, __kmap_atomic_idx);
-#endif
-
 /*
  * Virtual_count is not a pure "count".
  *  0 means that it is not mapped, and has not been mapped
@@ -370,6 +366,30 @@ EXPORT_SYMBOL(kunmap_high);
 #endif /* CONFIG_HIGHMEM */
 
 #ifdef CONFIG_KMAP_LOCAL
+
+static DEFINE_PER_CPU(int, __kmap_atomic_idx);
+
+static inline int kmap_atomic_idx_push(void)
+{
+	int idx = __this_cpu_inc_return(__kmap_atomic_idx) - 1;
+
+	WARN_ON_ONCE(in_irq() && !irqs_disabled());
+	BUG_ON(idx >= KM_TYPE_NR);
+	return idx;
+}
+
+static inline int kmap_atomic_idx(void)
+{
+	return __this_cpu_read(__kmap_atomic_idx) - 1;
+}
+
+static inline void kmap_atomic_idx_pop(void)
+{
+	int idx = __this_cpu_dec_return(__kmap_atomic_idx);
+
+	BUG_ON(idx < 0);
+}
+
 #ifndef arch_kmap_local_post_map
 # define arch_kmap_local_post_map(vaddr, pteval)	do { } while (0)
 #endif


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[patch V2 15/18] io-mapping: Cleanup atomic iomap

[Thomas Gleixner]

Switch the atomic iomap implementation over to kmap_local and stick the
preempt/pagefault mechanics into the generic code similar to the
kmap_atomic variants.

Rename the x86 map function in preparation for a non-atomic variant.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
V2: New patch to make review easier
---
 arch/x86/include/asm/iomap.h |    9 +--------
 arch/x86/mm/iomap_32.c       |    6 ++----
 include/linux/io-mapping.h   |    8 ++++++--
 3 files changed, 9 insertions(+), 14 deletions(-)

--- a/arch/x86/include/asm/iomap.h
+++ b/arch/x86/include/asm/iomap.h
@@ -13,14 +13,7 @@
 #include <asm/cacheflush.h>
 #include <asm/tlbflush.h>
 
-void __iomem *iomap_atomic_pfn_prot(unsigned long pfn, pgprot_t prot);
-
-static inline void iounmap_atomic(void __iomem *vaddr)
-{
-	kunmap_local_indexed((void __force *)vaddr);
-	pagefault_enable();
-	preempt_enable();
-}
+void __iomem *__iomap_local_pfn_prot(unsigned long pfn, pgprot_t prot);
 
 int iomap_create_wc(resource_size_t base, unsigned long size, pgprot_t *prot);
 
--- a/arch/x86/mm/iomap_32.c
+++ b/arch/x86/mm/iomap_32.c
@@ -44,7 +44,7 @@ void iomap_free(resource_size_t base, un
 }
 EXPORT_SYMBOL_GPL(iomap_free);
 
-void __iomem *iomap_atomic_pfn_prot(unsigned long pfn, pgprot_t prot)
+void __iomem *__iomap_local_pfn_prot(unsigned long pfn, pgprot_t prot)
 {
 	/*
 	 * For non-PAT systems, translate non-WB request to UC- just in
@@ -60,8 +60,6 @@ void __iomem *iomap_atomic_pfn_prot(unsi
 	/* Filter out unsupported __PAGE_KERNEL* bits: */
 	pgprot_val(prot) &= __default_kernel_pte_mask;
 
-	preempt_disable();
-	pagefault_disable();
 	return (void __force __iomem *)__kmap_local_pfn_prot(pfn, prot);
 }
-EXPORT_SYMBOL_GPL(iomap_atomic_pfn_prot);
+EXPORT_SYMBOL_GPL(__iomap_local_pfn_prot);
--- a/include/linux/io-mapping.h
+++ b/include/linux/io-mapping.h
@@ -69,13 +69,17 @@ io_mapping_map_atomic_wc(struct io_mappi
 
 	BUG_ON(offset >= mapping->size);
 	phys_addr = mapping->base + offset;
-	return iomap_atomic_pfn_prot(PHYS_PFN(phys_addr), mapping->prot);
+	preempt_disable();
+	pagefault_disable();
+	return __iomap_local_pfn_prot(PHYS_PFN(phys_addr), mapping->prot);
 }
 
 static inline void
 io_mapping_unmap_atomic(void __iomem *vaddr)
 {
-	iounmap_atomic(vaddr);
+	kunmap_local_indexed((void __force *)vaddr);
+	pagefault_enable();
+	preempt_enable();
 }
 
 static inline void __iomem *


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[patch V2 16/18] sched: highmem: Store local kmaps in task struct

[Thomas Gleixner]

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 <tglx@linutronix.de>
---
 include/linux/highmem.h |   10 +++++
 include/linux/sched.h   |    9 ++++
 kernel/entry/common.c   |    2 +
 kernel/fork.c           |    1 
 kernel/sched/core.c     |   18 +++++++++
 mm/highmem.c            |   96 +++++++++++++++++++++++++++++++++++++++++-------
 6 files changed, 123 insertions(+), 13 deletions(-)

--- a/include/linux/highmem.h
+++ b/include/linux/highmem.h
@@ -38,6 +38,16 @@ static inline void invalidate_kernel_vma
 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
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -34,6 +34,7 @@
 #include <linux/rseq.h>
 #include <linux/seqlock.h>
 #include <linux/kcsan.h>
+#include <asm/kmap_types.h>
 
 /* 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_TYPE_NR];
+#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
--- a/kernel/entry/common.c
+++ b/kernel/entry/common.c
@@ -2,6 +2,7 @@
 
 #include <linux/context_tracking.h>
 #include <linux/entry-common.h>
+#include <linux/highmem.h>
 #include <linux/livepatch.h>
 #include <linux/audit.h>
 
@@ -194,6 +195,7 @@ static void exit_to_user_mode_prepare(st
 
 	/* Ensure that the address limit is intact and no locks are held */
 	addr_limit_user_check();
+	kmap_assert_nomap();
 	lockdep_assert_irqs_disabled();
 	lockdep_sys_exit();
 }
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -930,6 +930,7 @@ static struct task_struct *dup_task_stru
 	account_kernel_stack(tsk, 1);
 
 	kcov_task_init(tsk);
+	kmap_local_fork(tsk);
 
 #ifdef CONFIG_FAULT_INJECTION
 	tsk->fail_nth = 0;
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -4053,6 +4053,22 @@ static inline void finish_lock_switch(st
 # define finish_arch_post_lock_switch()	do { } while (0)
 #endif
 
+static inline void kmap_local_sched_out(void)
+{
+#ifdef CONFIG_KMAP_LOCAL
+	if (unlikely(current->kmap_ctrl.idx))
+		__kmap_local_sched_out();
+#endif
+}
+
+static inline void kmap_local_sched_in(void)
+{
+#ifdef CONFIG_KMAP_LOCAL
+	if (unlikely(current->kmap_ctrl.idx))
+		__kmap_local_sched_in();
+#endif
+}
+
 /**
  * prepare_task_switch - prepare to switch tasks
  * @rq: the runqueue preparing to switch
@@ -4075,6 +4091,7 @@ prepare_task_switch(struct rq *rq, struc
 	perf_event_task_sched_out(prev, next);
 	rseq_preempt(prev);
 	fire_sched_out_preempt_notifiers(prev, next);
+	kmap_local_sched_out();
 	prepare_task(next);
 	prepare_arch_switch(next);
 }
@@ -4141,6 +4158,7 @@ static struct rq *finish_task_switch(str
 	finish_lock_switch(rq);
 	finish_arch_post_lock_switch();
 	kcov_finish_switch(current);
+	kmap_local_sched_in();
 
 	fire_sched_in_preempt_notifiers(current);
 	/*
--- a/mm/highmem.c
+++ b/mm/highmem.c
@@ -367,27 +367,24 @@ EXPORT_SYMBOL(kunmap_high);
 
 #ifdef CONFIG_KMAP_LOCAL
 
-static DEFINE_PER_CPU(int, __kmap_atomic_idx);
-
-static inline int kmap_atomic_idx_push(void)
+static inline int kmap_local_idx_push(void)
 {
-	int idx = __this_cpu_inc_return(__kmap_atomic_idx) - 1;
+	int idx = current->kmap_ctrl.idx++;
 
 	WARN_ON_ONCE(in_irq() && !irqs_disabled());
 	BUG_ON(idx >= KM_TYPE_NR);
 	return idx;
 }
 
-static inline int kmap_atomic_idx(void)
+static inline int kmap_local_idx(void)
 {
-	return __this_cpu_read(__kmap_atomic_idx) - 1;
+	return current->kmap_ctrl.idx - 1;
 }
 
-static inline void kmap_atomic_idx_pop(void)
+static inline void kmap_local_idx_pop(void)
 {
-	int idx = __this_cpu_dec_return(__kmap_atomic_idx);
-
-	BUG_ON(idx < 0);
+	current->kmap_ctrl.idx--;
+	BUG_ON(current->kmap_ctrl.idx < 0);
 }
 
 #ifndef arch_kmap_local_post_map
@@ -447,12 +444,13 @@ void *__kmap_local_pfn_prot(unsigned lon
 	int idx;
 
 	preempt_disable();
-	idx = arch_kmap_local_map_idx(kmap_atomic_idx_push(), pfn);
+	idx = arch_kmap_local_map_idx(kmap_local_idx_push(), pfn);
 	vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
 	BUG_ON(!pte_none(*(kmap_pte - idx)));
 	pteval = pfn_pte(pfn, prot);
 	set_pte_at(&init_mm, vaddr, kmap_pte - idx, pteval);
 	arch_kmap_local_post_map(vaddr, pteval);
+	current->kmap_ctrl.pteval[kmap_local_idx()] = pteval;
 	preempt_enable();
 
 	return (void *)vaddr;
@@ -491,16 +489,88 @@ void kunmap_local_indexed(void *vaddr)
 	}
 
 	preempt_disable();
-	idx = arch_kmap_local_unmap_idx(kmap_atomic_idx(), addr);
+	idx = arch_kmap_local_unmap_idx(kmap_local_idx(), addr);
 	WARN_ON_ONCE(addr != __fix_to_virt(FIX_KMAP_BEGIN + idx));
 
 	arch_kmap_local_pre_unmap(addr);
 	pte_clear(&init_mm, addr, kmap_pte - idx);
 	arch_kmap_local_post_unmap(addr);
-	kmap_atomic_idx_pop();
+	current->kmap_ctrl.pteval[kmap_local_idx()] = __pte(0);
+	kmap_local_idx_pop();
 	preempt_enable();
 }
 EXPORT_SYMBOL(kunmap_local_indexed);
+
+/*
+ * Invoked before switch_to(). This is safe even when during or after
+ * clearing the maps an interrupt which needs a kmap_local happens because
+ * the task::kmap_ctrl.idx is not modified by the unmapping code so a
+ * nested kmap_local will use the next unused index and restore the index
+ * on unmap. The already cleared kmaps of the outgoing task are irrelevant
+ * because the interrupt context does not know about them. The same applies
+ * when scheduling back in for an interrupt which happens before the
+ * restore is complete.
+ */
+void __kmap_local_sched_out(void)
+{
+	struct task_struct *tsk = current;
+	pte_t *kmap_pte = kmap_get_pte();
+	int i;
+
+	/* Clear kmaps */
+	for (i = 0; i < tsk->kmap_ctrl.idx; i++) {
+		pte_t pteval = tsk->kmap_ctrl.pteval[i];
+		unsigned long addr;
+		int idx;
+
+		if (WARN_ON_ONCE(pte_none(pteval)))
+			continue;
+
+		/*
+		 * This is a horrible hack for XTENSA to calculate the
+		 * coloured PTE index. Uses the PFN encoded into the pteval
+		 * and the map index calculation because the actual mapped
+		 * virtual address is not stored in task::kmap_ctrl.
+		 * For any sane architecture this is optimized out.
+		 */
+		idx = arch_kmap_local_map_idx(i, pte_pfn(pteval));
+
+		addr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
+		arch_kmap_local_pre_unmap(addr);
+		pte_clear(&init_mm, addr, kmap_pte - idx);
+		arch_kmap_local_post_unmap(addr);
+	}
+}
+
+void __kmap_local_sched_in(void)
+{
+	struct task_struct *tsk = current;
+	pte_t *kmap_pte = kmap_get_pte();
+	int i;
+
+	/* Restore kmaps */
+	for (i = 0; i < tsk->kmap_ctrl.idx; i++) {
+		pte_t pteval = tsk->kmap_ctrl.pteval[i];
+		unsigned long addr;
+		int idx;
+
+		if (WARN_ON_ONCE(pte_none(pteval)))
+			continue;
+
+		/* See comment in __kmap_local_sched_out() */
+		idx = arch_kmap_local_map_idx(i, pte_pfn(pteval));
+		addr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
+		set_pte_at(&init_mm, addr, kmap_pte - idx, pteval);
+		arch_kmap_local_post_map(addr, pteval);
+	}
+}
+
+void kmap_local_fork(struct task_struct *tsk)
+{
+	if (WARN_ON_ONCE(tsk->kmap_ctrl.idx))
+		memset(&tsk->kmap_ctrl, 0, sizeof(tsk->kmap_ctrl));
+}
+
 #endif
 
 #if defined(HASHED_PAGE_VIRTUAL)


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[patch V2 17/18] mm/highmem: Provide kmap_local*

[Thomas Gleixner]

Now that the kmap atomic index is stored in task struct provide a
preemptible variant. On context switch the maps of an outgoing task are
removed and the map of the incoming task are restored. That's obviously
slow, but highmem is slow anyway.

The kmap_local.*() functions can be invoked from both preemptible and
atomic context. kmap local sections disable migration to keep the resulting
virtual mapping address correct, but disable neither pagefaults nor
preemption.

A wholesale conversion of kmap_atomic to be fully preemptible is not
possible because some of the usage sites might rely on the preemption
disable for serialization or on the implicit pagefault disable. Needs to be
done on a case by case basis.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
V2: Make it more consistent and add commentry
---
 include/linux/highmem.h |  115 +++++++++++++++++++++++++++++++++++++++++-------
 1 file changed, 100 insertions(+), 15 deletions(-)

--- a/include/linux/highmem.h
+++ b/include/linux/highmem.h
@@ -86,17 +86,56 @@ static inline void kunmap(struct page *p
 }
 
 /*
- * kmap_atomic/kunmap_atomic is significantly faster than kmap/kunmap because
- * no global lock is needed and because the kmap code must perform a global TLB
- * invalidation when the kmap pool wraps.
- *
- * However when holding an atomic kmap it is not legal to sleep, so atomic
- * kmaps are appropriate for short, tight code paths only.
- *
- * The use of kmap_atomic/kunmap_atomic is discouraged - kmap/kunmap
- * gives a more generic (and caching) interface. But kmap_atomic can
- * be used in IRQ contexts, so in some (very limited) cases we need
- * it.
+ * For highmem systems it is required to temporarily map pages
+ * which reside in the portion of memory which is not covered
+ * by the permanent kernel mapping.
+ *
+ * This comes in three flavors:
+ *
+ * 1) kmap/kunmap:
+ *
+ *    An interface to acquire longer term mappings with no restrictions
+ *    on preemption and migration. This comes with an overhead as the
+ *    mapping space is restricted and protected by a global lock. It
+ *    also requires global TLB invalidation when the kmap pool wraps.
+ *
+ *    kmap() might block when the mapping space is fully utilized until a
+ *    slot becomes available. Only callable from preemptible thread
+ *    context.
+ *
+ * 2) kmap_local.*()/kunmap_local.*()
+ *
+ *    An interface to acquire short term mappings. Can be invoked from any
+ *    context including interrupts. The mapping is per thread, CPU local
+ *    and not globaly visible. It can only be used in the context which
+ *    acquried the mapping. Nesting kmap_local.*() and kmap_atomic.*()
+ *    mappings is allowed to a certain extent (up to KMAP_TYPE_NR).
+ *
+ *    Nested kmap_local.*() and kunmap_local.*() invocations have to be
+ *    strictly ordered because the map implementation is stack based.
+ *
+ *    kmap_local.*() disables migration, but keeps preemption enabled. It's
+ *    valid to take pagefaults in a kmap_local region unless the context in
+ *    which the local kmap is acquired does not allow it for other reasons.
+ *
+ *    If a task holding local kmaps is preempted, the maps are removed on
+ *    context switch and restored when the task comes back on the CPU. As
+ *    the maps are strictly CPU local it is guaranteed that the task stays
+ *    on the CPU and the CPU cannot be unplugged until the local kmaps are
+ *    released.
+ *
+ * 3) kmap_atomic.*()/kunmap_atomic.*()
+ *
+ *    Based on the same mechanism as kmap local. Atomic kmap disables
+ *    preemption and pagefaults. Only use if absolutely required, use
+ *    the corresponding kmap_local variant if possible.
+ *
+ * Local and atomic kmaps are faster than kmap/kunmap, but impose
+ * restrictions. Only use them when required.
+ *
+ * For !HIGHMEM enabled systems the kmap flavours are not doing any mapping
+ * operation and kmap() won't sleep, but the kmap local and atomic variants
+ * still disable migration resp. pagefaults and preemption.
  */
 static inline void *kmap_atomic_prot(struct page *page, pgprot_t prot)
 {
@@ -122,6 +161,28 @@ static inline void __kunmap_atomic(void
 	kunmap_local_indexed(addr);
 }
 
+static inline void *kmap_local_page_prot(struct page *page, pgprot_t prot)
+{
+	migrate_disable();
+	return __kmap_local_page_prot(page, prot);
+}
+
+static inline void *kmap_local_page(struct page *page)
+{
+	return kmap_local_page_prot(page, kmap_prot);
+}
+
+static inline void *kmap_local_pfn(unsigned long pfn)
+{
+	migrate_disable();
+	return __kmap_local_pfn_prot(pfn, kmap_prot);
+}
+
+static inline void __kunmap_local(void *vaddr)
+{
+	kunmap_local_indexed(vaddr);
+}
+
 /* declarations for linux/mm/highmem.c */
 unsigned int nr_free_highpages(void);
 extern atomic_long_t _totalhigh_pages;
@@ -201,10 +262,27 @@ static inline void *kmap_atomic_pfn(unsi
 
 static inline void __kunmap_atomic(void *addr)
 {
-	/*
-	 * Mostly nothing to do in the CONFIG_HIGHMEM=n case as kunmap_atomic()
-	 * handles re-enabling faults and preemption
-	 */
+	__kunmap_local(addr);
+}
+
+static inline void *kmap_local_page(struct page *page)
+{
+	migrate_disable();
+	return page_address(page);
+}
+
+static inline void *kmap_local_page_prot(struct page *page, pgprot_t prot)
+{
+	return kmap_local_page(page);
+}
+
+static inline void *kmap_local_pfn(unsigned long pfn)
+{
+	return kmap_local_page(pfn_to_page(pfn));
+}
+
+static inline void __kunmap_local(void *addr)
+{
 #ifdef ARCH_HAS_FLUSH_ON_KUNMAP
 	kunmap_flush_on_unmap(addr);
 #endif
@@ -226,6 +304,13 @@ do {								\
 	preempt_enable();					\
 } while (0)
 
+#define kunmap_local(__addr)					\
+do {								\
+	BUILD_BUG_ON(__same_type((__addr), struct page *));	\
+	__kunmap_local(__addr);					\
+	migrate_enable();					\
+} while (0)
+
 /* when CONFIG_HIGHMEM is not set these will be plain clear/copy_page */
 #ifndef clear_user_highpage
 static inline void clear_user_highpage(struct page *page, unsigned long vaddr)


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[patch V2 18/18] io-mapping: Provide iomap_local variant

[Thomas Gleixner]

Similar to kmap local provide a iomap local variant which only disables
migration, but neither disables pagefaults nor preemption.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
V2: Split out from the large combo patch and add the !IOMAP_ATOMIC variants
---
 include/linux/io-mapping.h |   34 ++++++++++++++++++++++++++++++++--
 1 file changed, 32 insertions(+), 2 deletions(-)

--- a/include/linux/io-mapping.h
+++ b/include/linux/io-mapping.h
@@ -83,6 +83,23 @@ io_mapping_unmap_atomic(void __iomem *va
 }
 
 static inline void __iomem *
+io_mapping_map_local_wc(struct io_mapping *mapping, unsigned long offset)
+{
+	resource_size_t phys_addr;
+
+	BUG_ON(offset >= mapping->size);
+	phys_addr = mapping->base + offset;
+	migrate_disable();
+	return __iomap_local_pfn_prot(PHYS_PFN(phys_addr), mapping->prot);
+}
+
+static inline void io_mapping_unmap_local(void __iomem *vaddr)
+{
+	kunmap_local_indexed((void __force *)vaddr);
+	migrate_enable();
+}
+
+static inline void __iomem *
 io_mapping_map_wc(struct io_mapping *mapping,
 		  unsigned long offset,
 		  unsigned long size)
@@ -101,7 +118,7 @@ io_mapping_unmap(void __iomem *vaddr)
 	iounmap(vaddr);
 }
 
-#else
+#else  /* HAVE_ATOMIC_IOMAP */
 
 #include <linux/uaccess.h>
 
@@ -166,7 +183,20 @@ io_mapping_unmap_atomic(void __iomem *va
 	preempt_enable();
 }
 
-#endif /* HAVE_ATOMIC_IOMAP */
+static inline void __iomem *
+io_mapping_map_local_wc(struct io_mapping *mapping, unsigned long offset)
+{
+	migrate_disable();
+	return io_mapping_map_wc(mapping, offset, PAGE_SIZE);
+}
+
+static inline void io_mapping_unmap_local(void __iomem *vaddr)
+{
+	io_mapping_unmap(vaddr);
+	migrate_enable();
+}
+
+#endif /* !HAVE_ATOMIC_IOMAP */
 
 static inline struct io_mapping *
 io_mapping_create_wc(resource_size_t base,


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Re: [patch V2 00/18] mm/highmem: Preemptible variant of kmap_atomic & friends

[Linus Torvalds]

On Thu, Oct 29, 2020 at 3:32 PM Thomas Gleixner <tglx@linutronix.de> wrote:
>
>
> Though I wanted to share the current state of affairs before investigating
> that further. If there is consensus in going forward with this, I'll have a
> deeper look into this issue.

Me likee. I think this looks like the right thing to do.

I didn't actually apply the patches, but just from reading them it
_looks_ to me like you do the migrate_disable() unconditionally, even
if it's not a highmem page..

That sounds like it might be a good thing for debugging, but not
necessarily great in general.

Or am I misreading things?

                Linus

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Re: [patch V2 00/18] mm/highmem: Preemptible variant of kmap_atomic & friends

[Thomas Gleixner]

On Thu, Oct 29 2020 at 16:11, Linus Torvalds wrote:
> On Thu, Oct 29, 2020 at 3:32 PM Thomas Gleixner <tglx@linutronix.de> wrote:
>>
>> Though I wanted to share the current state of affairs before investigating
>> that further. If there is consensus in going forward with this, I'll have a
>> deeper look into this issue.
>
> Me likee. I think this looks like the right thing to do.
>
> I didn't actually apply the patches, but just from reading them it
> _looks_ to me like you do the migrate_disable() unconditionally, even
> if it's not a highmem page..
>
> That sounds like it might be a good thing for debugging, but not
> necessarily great in general.
>
> Or am I misreading things?

No, you're not misreading it, but doing it conditionally would be a
complete semantical disaster. kmap_atomic*() also disables preemption
and pagefaults unconditionaly.  If that wouldn't be the case then every
caller would have to have conditionals like 'if (CONFIG_HIGHMEM)' or
worse 'if (PageHighMem(page)'.

Let's not go there.

Migrate disable is a less horrible plague than preempt and pagefault
disable even if the scheduler people disagree due to the lack of theory
backing that up :)

The charm of the new interface is that users still can rely on per
cpuness independent of being on a highmem plagued system. For non
highmem systems the extra migrate disable/enable is really a minor
nuissance.

Thanks,

        tglx

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Re: [patch V2 00/18] mm/highmem: Preemptible variant of kmap_atomic & friends

[Christoph Hellwig]

On Thu, Oct 29, 2020 at 11:18:06PM +0100, Thomas Gleixner wrote:
> This is achieved by:

...

> 
>  - Consolidating all kmap atomic implementations in generic code

...

> Though I wanted to share the current state of affairs before investigating
> that further. If there is consensus in going forward with this, I'll have a
> deeper look into this issue.

I think the consolidation is a winner no matter where we go next.  Maybe
split it out in a prep series so we can get it in ASAP?

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Re: [patch V2 00/18] mm/highmem: Preemptible variant of kmap_atomic & friends

[Thomas Gleixner]

On Fri, Oct 30 2020 at 00:41, Thomas Gleixner wrote:
> On Thu, Oct 29 2020 at 16:11, Linus Torvalds wrote:
> No, you're not misreading it, but doing it conditionally would be a
> complete semantical disaster. kmap_atomic*() also disables preemption
> and pagefaults unconditionaly.  If that wouldn't be the case then every
> caller would have to have conditionals like 'if (CONFIG_HIGHMEM)' or
> worse 'if (PageHighMem(page)'.
>
> Let's not go there.
>
> Migrate disable is a less horrible plague than preempt and pagefault
> disable even if the scheduler people disagree due to the lack of theory
> backing that up :)
>
> The charm of the new interface is that users still can rely on per
> cpuness independent of being on a highmem plagued system. For non
> highmem systems the extra migrate disable/enable is really a minor
> nuissance.

thinking about it some more after having sleep and coffee, we actually
could hide the migrate disable in the actual highmem part.

But then we really should not name it kmap_local. 'local' suggests
locality, think local_irq*, local_bh* ... kmap_task would be more
accurate then.

Toughts?

        tglx

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Re: [patch V2 00/18] mm/highmem: Preemptible variant of kmap_atomic & friends

[Thomas Gleixner]

On Fri, Oct 30 2020 at 08:25, Christoph Hellwig wrote:
> On Thu, Oct 29, 2020 at 11:18:06PM +0100, Thomas Gleixner wrote:
>>  - Consolidating all kmap atomic implementations in generic code
>
> I think the consolidation is a winner no matter where we go next.  Maybe
> split it out in a prep series so we can get it in ASAP?

Yes, patch 2-15 can just go without any dependency. The only thing which
needs a bit of thought is naming. See the other reply to Linus.

Thanks,

        tglx

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Re: [patch V2 00/18] mm/highmem: Preemptible variant of kmap_atomic & friends

[Matthew Wilcox]

On Thu, Oct 29, 2020 at 11:18:06PM +0100, Thomas Gleixner wrote:
> This series provides kmap_local.* iomap_local variants which only disable
> migration to keep the virtual mapping address stable accross preemption,
> but do neither disable pagefaults nor preemption. The new functions can be
> used in any context, but if used in atomic context the caller has to take
> care of eventually disabling pagefaults.

Could I ask for a CONFIG_KMAP_DEBUG which aliases all the kmap variants
to vmap()?  I think we currently have a problem in iov_iter on HIGHMEM
configs:

copy_page_to_iter() calls page_copy_sane() which checks:

        head = compound_head(page);
        if (likely(n <= v && v <= page_size(head)))
                return true;

but then:

                void *kaddr = kmap_atomic(page);
                size_t wanted = copy_to_iter(kaddr + offset, bytes, i);
                kunmap_atomic(kaddr);

so if offset to offset+bytes is larger than PAGE_SIZE, this is going to
work for lowmem pages and fail miserably for highmem pages.  I suggest
vmap() because vmap has a PAGE_SIZE gap between each allocation.

Alternatively if we could have a kmap_atomic_compound(), that would
be awesome, but probably not realistic to implement.  I've more
or less resigned myself to having to map things one page at a time.

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Re: [patch V2 00/18] mm/highmem: Preemptible variant of kmap_atomic & friends

[Thomas Gleixner]

On Fri, Oct 30 2020 at 13:06, Matthew Wilcox wrote:
> On Thu, Oct 29, 2020 at 11:18:06PM +0100, Thomas Gleixner wrote:
>> This series provides kmap_local.* iomap_local variants which only disable
>> migration to keep the virtual mapping address stable accross preemption,
>> but do neither disable pagefaults nor preemption. The new functions can be
>> used in any context, but if used in atomic context the caller has to take
>> care of eventually disabling pagefaults.
>
> Could I ask for a CONFIG_KMAP_DEBUG which aliases all the kmap variants
> to vmap()?  I think we currently have a problem in iov_iter on HIGHMEM
> configs:

For kmap() that would work, but for kmap_atomic() not so much when it is
called in non-preemptible context because vmap() might sleep.

> copy_page_to_iter() calls page_copy_sane() which checks:
>
>         head = compound_head(page);
>         if (likely(n <= v && v <= page_size(head)))
>                 return true;
>
> but then:
>
>                 void *kaddr = kmap_atomic(page);
>                 size_t wanted = copy_to_iter(kaddr + offset, bytes, i);
>                 kunmap_atomic(kaddr);
>
> so if offset to offset+bytes is larger than PAGE_SIZE, this is going to
> work for lowmem pages and fail miserably for highmem pages.  I suggest
> vmap() because vmap has a PAGE_SIZE gap between each allocation.

On 32bit highmem the kmap_atomic() case is easy: Double the number of
mapping slots and only use every second one, which gives you a guard
page between the maps.

For 64bit we could do something ugly: Enable the highmem kmap_atomic()
crud and enforce an alias mapping (at least on the architectures where
this is reasonable). Then you get the same as for 32bit.

> Alternatively if we could have a kmap_atomic_compound(), that would
> be awesome, but probably not realistic to implement.  I've more
> or less resigned myself to having to map things one page at a time.

That might be horribly awesome on 32bit :)

Thanks,

        tglx

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Re: [patch V2 00/18] mm/highmem: Preemptible variant of kmap_atomic & friends

[Linus Torvalds]

On Fri, Oct 30, 2020 at 2:39 AM Thomas Gleixner <tglx@linutronix.de> wrote:
>
> But then we really should not name it kmap_local. 'local' suggests
> locality, think local_irq*, local_bh* ... kmap_task would be more
> accurate then.

So the main reason I'd like to see it is because I think on a
non-highmem machine, the new kmap should be a complete no-op. IOW,
we'd make sure that there are no costs, no need to increment any
"restrict migration" counts etc.

It's been a bit of a pain to have kmap_atomic() have magical side
semantics that people might then depend on.

I think "local" could still work as a name, because it would have to
be thread-local (and maybe we'd want a debug mode where that gets
verified, as actual HIGHMEM machines are getting rare).

I'd avoid "task", because that implies (to me, at least) that it
wouldn't be good for interrupts etc that don't have a task context.

I think the main issue is that it has to be released in the same
context as it was created (ie no passing those things around to other
contexts). I think "local" is fine for that, but I could imagine other
names. The ones that come to mind are somewhat cumbersome, though
("shortterm" or "local_ctx" or something along those lines).

I dunno.

              Linus

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Re: [patch V2 00/18] mm/highmem: Preemptible variant of kmap_atomic & friends

[Thomas Gleixner]

On Fri, Oct 30 2020 at 13:28, Linus Torvalds wrote:
> On Fri, Oct 30, 2020 at 2:39 AM Thomas Gleixner <tglx@linutronix.de> wrote:
>>
>> But then we really should not name it kmap_local. 'local' suggests
>> locality, think local_irq*, local_bh* ... kmap_task would be more
>> accurate then.
>
> So the main reason I'd like to see it is because I think on a
> non-highmem machine, the new kmap should be a complete no-op. IOW,
> we'd make sure that there are no costs, no need to increment any
> "restrict migration" counts etc.

Fair enough.

> It's been a bit of a pain to have kmap_atomic() have magical side
> semantics that people might then depend on.

kmap_atomic() will still have the side semantics :)

> I think "local" could still work as a name, because it would have to
> be thread-local (and maybe we'd want a debug mode where that gets
> verified, as actual HIGHMEM machines are getting rare).
>
> I'd avoid "task", because that implies (to me, at least) that it
> wouldn't be good for interrupts etc that don't have a task context.
>
> I think the main issue is that it has to be released in the same
> context as it was created (ie no passing those things around to other
> contexts). I think "local" is fine for that, but I could imagine other
> names. The ones that come to mind are somewhat cumbersome, though
> ("shortterm" or "local_ctx" or something along those lines).

Yeah, not really intuitive either.

Let's stick with _local and add proper function documentation which
clearly says, that the side effect of non-migratability applies only for
the 32bit highmem case in order to make it work at all.

So code which needs CPU locality cannot rely on it and we have enough
debug stuff to catch something like:

    kmap_local()
    this_cpu_write(....)
    kunmap_local()

Let me redo the pile.

While at it I might have a look at that debug request from Willy in the
other end of this thread. Any comment on that?

 https://lore.kernel.org/r/87k0v7mrrd.fsf@nanos.tec.linutronix.de

Thanks,

        tglx


      

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Re: [patch V2 00/18] mm/highmem: Preemptible variant of kmap_atomic & friends

[Linus Torvalds]

On Fri, Oct 30, 2020 at 3:26 PM Thomas Gleixner <tglx@linutronix.de> wrote:
>
> While at it I might have a look at that debug request from Willy in the
> other end of this thread. Any comment on that?
>
>  https://lore.kernel.org/r/87k0v7mrrd.fsf@nanos.tec.linutronix.de

I do think that it would be nice to have a debug mode, particularly
since over the last few years we've really lost a lot of HIGHMEM
coverage (to the point that I've wondered how worthwhile it really is
to support at all any more - I think it's Arnd who argued that it's
mainly some embedded ARM variants that will want it for the forseeable
future).

So I'm honestly somewhat torn. I think HIGHMEM is dying, and yes that
argues for "non-HIGHMEM had better have some debug coverage", but at
the same time I think it doesn't even really matter any more. At some
point those embedded ARM platforms just aren't even interesting - they
might as well use older kernels if they are the only thing really
arguing for HIGHMEM at all.

This is one reason why I'd like the new kmap_local() to be a no-op,
and I'd prefer for it to have no other side effects - because I want
to be ready to remove it entirely some day. And if we end up having
some transition where people start rewriting "kmap_atomic()" to be
"kmap_local() + explicit preemption disable", then I think that would
be a good step on that whole "kmap will eventually go away" path.

But I do *not* believe that we need to add _so_ much debug support
that we'd catch Willy's "more than one page" case. And I absolutely do
not believe for a second that we should start caring about compound
pages. NO. kmap() is almost dead already, we're not making it worse.

To me, your patch series has two big advantages:

 - more common code

 - kmap_local() becomes more of a no-op

and the last thing we want is to expand on kmap.

           Linus

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Re: [patch V2 00/18] mm/highmem: Preemptible variant of kmap_atomic & friends

[Thomas Gleixner]

On Fri, Oct 30 2020 at 15:46, Linus Torvalds wrote:
> On Fri, Oct 30, 2020 at 3:26 PM Thomas Gleixner <tglx@linutronix.de> wrote:
> To me, your patch series has two big advantages:
>
>  - more common code
>
>  - kmap_local() becomes more of a no-op
>
> and the last thing we want is to expand on kmap.

Happy to go with that.

While trying to document the mess, I just stumbled over the abuse of
kmap_atomic_prot() in

drivers/gpu/drm/ttm/ttm_bo_util.c:      dst = kmap_atomic_prot(d, prot);
drivers/gpu/drm/ttm/ttm_bo_util.c:      src = kmap_atomic_prot(s, prot);
drivers/gpu/drm/vmwgfx/vmwgfx_blit.c:   kmap_atomic_prot(d->dst_pages[dst_page],
drivers/gpu/drm/vmwgfx/vmwgfx_blit.c:   kmap_atomic_prot(d->src_pages[src_page],

For !HIGHMEM kmap_atomic_prot() just ignores the 'prot' argument and
returns the page address. 

Moar patches to be written ... Sigh!

Thanks,

        tglx





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Re: [patch V2 00/18] mm/highmem: Preemptible variant of kmap_atomic & friends

[Thomas Gleixner]

On Sat, Oct 31 2020 at 00:26, Thomas Gleixner wrote:

> On Fri, Oct 30 2020 at 15:46, Linus Torvalds wrote:
>> On Fri, Oct 30, 2020 at 3:26 PM Thomas Gleixner <tglx@linutronix.de> wrote:
>> To me, your patch series has two big advantages:
>>
>>  - more common code
>>
>>  - kmap_local() becomes more of a no-op
>>
>> and the last thing we want is to expand on kmap.
>
> Happy to go with that.
>
> While trying to document the mess, I just stumbled over the abuse of
> kmap_atomic_prot() in
>
> drivers/gpu/drm/ttm/ttm_bo_util.c:      dst = kmap_atomic_prot(d, prot);
> drivers/gpu/drm/ttm/ttm_bo_util.c:      src = kmap_atomic_prot(s, prot);
> drivers/gpu/drm/vmwgfx/vmwgfx_blit.c:   kmap_atomic_prot(d->dst_pages[dst_page],
> drivers/gpu/drm/vmwgfx/vmwgfx_blit.c:   kmap_atomic_prot(d->src_pages[src_page],
>
> For !HIGHMEM kmap_atomic_prot() just ignores the 'prot' argument and
> returns the page address. 
>
> Moar patches to be written ... Sigh!

Or not. This is actually correct by some definition of correct. For
the non highmem case pgprot is set via the set_memory_*() functions and
this just handles the highmem case.

Comments are overrrated...

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Re: [patch V2 00/18] mm/highmem: Preemptible variant of kmap_atomic & friends

[Arnd Bergmann]

On Fri, Oct 30, 2020 at 11:46 PM Linus Torvalds
<torvalds@linux-foundation.org> wrote:
>
> On Fri, Oct 30, 2020 at 3:26 PM Thomas Gleixner <tglx@linutronix.de> wrote:
> >
> > While at it I might have a look at that debug request from Willy in the
> > other end of this thread. Any comment on that?
> >
> >  https://lore.kernel.org/r/87k0v7mrrd.fsf@nanos.tec.linutronix.de
>
> I do think that it would be nice to have a debug mode, particularly
> since over the last few years we've really lost a lot of HIGHMEM
> coverage (to the point that I've wondered how worthwhile it really is
> to support at all any more - I think it's Arnd who argued that it's
> mainly some embedded ARM variants that will want it for the forseeable
> future).
>
> So I'm honestly somewhat torn. I think HIGHMEM is dying, and yes that
> argues for "non-HIGHMEM had better have some debug coverage", but at
> the same time I think it doesn't even really matter any more.

Shifting the testing of highmem code to the actual users of highmem
sounds reasonable to me. This means it will get broken more often,
but if it doesn't happen all the time, it might serve as a canary:
once a bug survives for long enough, we have a good indication that
users stopped caring ;-)

> At some
> point those embedded ARM platforms just aren't even interesting - they
> might as well use older kernels if they are the only thing really
> arguing for HIGHMEM at all.

Agreed, but it does need a little time to get there. My best guess is three
to five years from now we can remove it for good, provided a few things
happen first:

1. The remaining users of TI Keystone2, NXP i.MX6 Quad(Plus) and
  Renesas R8A7790/R8A7791/R8A7742/R8A7743 that use the
  largest memory configuration must have stopped requiring kernel
  version updates.
  These were all introduced at the peak of 32-bit Arm embedded
  systems around 2013, but they have long (15+ year) product
  life cycles and users pick these because they do promise kernel
  updates, unlike other SoC families that get stuck on old vendor
  kernels much earlier.

2. The plan to add a CONFIG_VMSPLIT_4G_4G option on arch/arm/
  must work out. We don't have all the code yet, and so far it looks
  like it's going to be a bit ugly and a bit slow but not nearly as ugly
  or slow as it was on x86 20 years ago.
  This would cover Cortex-A7/A15 systems from 2GB to 4GB,
  which are still fairly common and need to keep using mainline
  kernels for much longer than the system in point 1.
  It won't help on Cortex-A9 machines with 2GB, which I hope can
  migrate CONFIG_VMSPLIT_2G_OPT as a fallback.

3. No new systems with larger memory must appear. I noticed that
  e.g. the newly introduced Rockchips RV1109 and Allwinner
  A50/R328/V316 support LP-DDR4 on a dual Cortex-A7, but I
  hope that nobody will in practice combine a $2 SoC with a $15
  memory chip.
  Most other 32-bit chips use DDR3, which tends to prohibit
  configurations over 4GB in new designs, with the cheapest
  ones limited to 512MB (a single 256Mx16 chip) and the
  high end having already moved on to 64 bit.

Regarding 32-bit non-Arm systems, support for the MIPS-based
Baikal T1 was merged earlier this year and is used in Russian
PC style systems with up to 8GB.
There are also some users on 10+ year old 32-bit netbooks or
business laptops, both x86 and Apple G4.
The longest-lived 32-bit embedded systems with large memory
(other than Arm) are probably NXP QorIQ P20xx/P40xx used in
military VME bus systems, and low-end embedded systems based
on Vortex86.
I'm less worried about all of these because upstream kernel
support for ppc32 and x86-32 is already bitrotting and they will
likely get stuck on the last working kernel before the
TI/Renesas/NXP Arm systems do.

       Arnd

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Re: [patch V2 00/18] mm/highmem: Preemptible variant of kmap_atomic & friends

[Christophe Leroy]

> There are also some users on 10+ year old 32-bit netbooks or
> business laptops, both x86 and Apple G4.
> The longest-lived 32-bit embedded systems with large memory
> (other than Arm) are probably NXP QorIQ P20xx/P40xx used in
> military VME bus systems, and low-end embedded systems based
> on Vortex86.
> I'm less worried about all of these because upstream kernel
> support for ppc32 and x86-32 is already bitrotting and they will
> likely get stuck on the last working kernel before the
> TI/Renesas/NXP Arm systems do.
>

Upstream kernel support for ppc32 is bitrotting, seriously ? What do  
you mean exactly ?

ppc32 is actively supported, with recent addition of support of  
hugepages, kasan, uaccess protection, VMAP stack, etc ...

Christophe



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Re: [patch V2 00/18] mm/highmem: Preemptible variant of kmap_atomic & friends

[Arnd Bergmann]

On Sat, Oct 31, 2020 at 4:04 PM Christophe Leroy
<christophe.leroy@csgroup.eu> wrote:
> > There are also some users on 10+ year old 32-bit netbooks or
> > business laptops, both x86 and Apple G4.
> > The longest-lived 32-bit embedded systems with large memory
> > (other than Arm) are probably NXP QorIQ P20xx/P40xx used in
> > military VME bus systems, and low-end embedded systems based
> > on Vortex86.
> > I'm less worried about all of these because upstream kernel
> > support for ppc32 and x86-32 is already bitrotting and they will
> > likely get stuck on the last working kernel before the
> > TI/Renesas/NXP Arm systems do.
> >
>
> Upstream kernel support for ppc32 is bitrotting, seriously ? What do
> you mean exactly ?

I was thinking more of the platform support: out of the twelve
32-bit platforms in arch/powerpc/platforms/, your 8xx is the only
one listed as 'maintained' or 'supported' in the maintainers list,
and that seems to accurately describe the current state.

Freescale seems to have practically stopped contributing to any of
their 32-bit platforms in 2016 after the NXP acquisition and no longer
employing either of the maintainers. Similarly, Ben seems to have
stopped working on powermac in 2016, which was ten years after
the last 32-bit hardware shipped for that platform.

> ppc32 is actively supported, with recent addition of support of
> hugepages, kasan, uaccess protection, VMAP stack, etc ...

That is good to hear, I didn't know about these additions.
What platforms are people using to develop these? Is this
mainly your 8xx work, or is there ongoing development for
platforms that need highmem?

         Arnd

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Re: [patch V2 00/18] mm/highmem: Preemptible variant of kmap_atomic & friends

[Thomas Gleixner]

On Thu, Oct 29 2020 at 23:18, Thomas Gleixner wrote:
>
> There is also a still to be investigated question from Linus on the initial
> posting versus the per cpu / per task mapping stack depth which might need
> to be made larger due to the ability to take page faults within a mapping
> region.

I looked deeper into that and we have a stack depth of 20. That's plenty
and I couldn't find a way to get above 10 nested ones including faults,
interrupts, softirqs. With some stress testing I was not able to get over
a maximum of 6 according to the traceprintk I added.

For some obscure reason when CONFIG_DEBUG_HIGHMEM is enabled the stack
depth is increased from 20 to 41. But the only thing DEBUG_HIGHMEM does
is to enable a few BUG_ON()'s in the mapping code.

That's a leftover from the historical mapping code which had fixed
entries for various purposes. DEBUG_HIGHMEM inserted guard mappings
between the map types. But that got all ditched when kmap_atomic()
switched to a stack based map management. Though the WITH_KM_FENCE magic
survived without being functional. All the thing does today is to
increase the stack depth.

I just made that functional again by keeping the stack depth increase
and utilizing every second slot. That should catch Willy's mapping
problem nicely if he bothers to test on 32bit :)

Thanks,

        tglx


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