[PATCH v5 1/4] mm: Make lazy MMU mode context-aware

[Alexander Gordeev <agordeev@linux.ibm.com>]

Lazy MMU mode is assumed to be context-independent, in the sense
that it does not need any additional information while operating.
However, the s390 architecture benefits from knowing the exact
page table entries being modified.

Introduce lazy_mmu_mode_enable_with_ptes(), which is provided with
the process address space and the page table being operated on.
This information is required to enable s390-specific optimizations.

The function takes parameters that are typically passed to page-
table level walkers, which implies that the span of PTE entries
never crosses a page table boundary.

Architectures that do not require such information simply do not
need to define the lazy_mmu_mode_enable_with_ptes() callback.

Reviewed-by: Kevin Brodsky <kevin.brodsky@arm.com>
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>
---
 fs/proc/task_mmu.c      |  2 +-
 include/linux/pgtable.h | 46 +++++++++++++++++++++++++++++++++++++++++
 mm/madvise.c            |  8 +++----
 mm/memory.c             |  8 +++----
 mm/mprotect.c           |  2 +-
 mm/mremap.c             |  2 +-
 mm/vmalloc.c            |  6 +++---
 7 files changed, 60 insertions(+), 14 deletions(-)

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index d32408f7cd5e..750f6095147f 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -2842,7 +2842,7 @@ static int pagemap_scan_pmd_entry(pmd_t *pmd, unsigned long start,
 		return 0;
 	}
 
-	lazy_mmu_mode_enable();
+	lazy_mmu_mode_enable_with_ptes(vma->vm_mm, start, end, start_pte);
 
 	if ((p->arg.flags & PM_SCAN_WP_MATCHING) && !p->vec_out) {
 		/* Fast path for performing exclusive WP */
diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
index 2981e386da7b..cc85daf30739 100644
--- a/include/linux/pgtable.h
+++ b/include/linux/pgtable.h
@@ -271,6 +271,50 @@ static inline void lazy_mmu_mode_enable(void)
 		arch_enter_lazy_mmu_mode();
 }
 
+#ifndef arch_enter_lazy_mmu_mode_with_ptes
+static inline void arch_enter_lazy_mmu_mode_with_ptes(struct mm_struct *mm,
+		unsigned long addr, unsigned long end, pte_t *ptep)
+{
+	arch_enter_lazy_mmu_mode();
+}
+#endif
+
+/**
+ * lazy_mmu_mode_enable_with_ptes() - Enable the lazy MMU mode with a speedup hint.
+ * @mm: Address space the pages are mapped into.
+ * @addr: Start address of the range.
+ * @end: End address of the range.
+ * @ptep: Page table pointer for the first entry.
+ *
+ * Enters a new lazy MMU mode section; if the mode was not already enabled,
+ * enables it and calls arch_enter_lazy_mmu_mode_with_ptes().
+ *
+ * PTEs that fall within the specified range might observe update speedups.
+ * The PTEs must belong to the specified address space and be in the same PMD.
+ *
+ * There are no requirements on the order or range completeness of PTE
+ * updates for the specified range.
+ *
+ * Must be paired with a call to lazy_mmu_mode_disable().
+ *
+ * Has no effect if called:
+ * - While paused - see lazy_mmu_mode_pause()
+ * - In interrupt context
+ */
+static inline void lazy_mmu_mode_enable_with_ptes(struct mm_struct *mm,
+		unsigned long addr, unsigned long end, pte_t *ptep)
+{
+	struct lazy_mmu_state *state = &current->lazy_mmu_state;
+
+	if (in_interrupt() || state->pause_count > 0)
+		return;
+
+	VM_WARN_ON_ONCE(state->enable_count == U8_MAX);
+
+	if (state->enable_count++ == 0)
+		arch_enter_lazy_mmu_mode_with_ptes(mm, addr, end, ptep);
+}
+
 /**
  * lazy_mmu_mode_disable() - Disable the lazy MMU mode.
  *
@@ -387,6 +431,8 @@ static inline void lazy_mmu_mode_resume(void)
 }
 #else
 static inline void lazy_mmu_mode_enable(void) {}
+static inline void lazy_mmu_mode_enable_with_ptes(struct mm_struct *mm,
+		unsigned long addr, unsigned long end, pte_t *ptep) {}
 static inline void lazy_mmu_mode_disable(void) {}
 static inline void lazy_mmu_mode_pause(void) {}
 static inline void lazy_mmu_mode_resume(void) {}
diff --git a/mm/madvise.c b/mm/madvise.c
index 77552b03d318..4419d16b39f9 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -452,7 +452,7 @@ static int madvise_cold_or_pageout_pte_range(pmd_t *pmd,
 	if (!start_pte)
 		return 0;
 	flush_tlb_batched_pending(mm);
-	lazy_mmu_mode_enable();
+	lazy_mmu_mode_enable_with_ptes(mm, addr, end, start_pte);
 	for (; addr < end; pte += nr, addr += nr * PAGE_SIZE) {
 		nr = 1;
 		ptent = ptep_get(pte);
@@ -507,7 +507,7 @@ static int madvise_cold_or_pageout_pte_range(pmd_t *pmd,
 				if (!start_pte)
 					break;
 				flush_tlb_batched_pending(mm);
-				lazy_mmu_mode_enable();
+				lazy_mmu_mode_enable_with_ptes(mm, addr, end, start_pte);
 				if (!err)
 					nr = 0;
 				continue;
@@ -674,7 +674,7 @@ static int madvise_free_pte_range(pmd_t *pmd, unsigned long addr,
 	if (!start_pte)
 		return 0;
 	flush_tlb_batched_pending(mm);
-	lazy_mmu_mode_enable();
+	lazy_mmu_mode_enable_with_ptes(mm, addr, end, start_pte);
 	for (; addr != end; pte += nr, addr += PAGE_SIZE * nr) {
 		nr = 1;
 		ptent = ptep_get(pte);
@@ -734,7 +734,7 @@ static int madvise_free_pte_range(pmd_t *pmd, unsigned long addr,
 				if (!start_pte)
 					break;
 				flush_tlb_batched_pending(mm);
-				lazy_mmu_mode_enable();
+				lazy_mmu_mode_enable_with_ptes(mm, addr, end, pte);
 				if (!err)
 					nr = 0;
 				continue;
diff --git a/mm/memory.c b/mm/memory.c
index ff338c2abe92..ee1770ff4a64 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1272,7 +1272,7 @@ copy_pte_range(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma,
 	spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
 	orig_src_pte = src_pte;
 	orig_dst_pte = dst_pte;
-	lazy_mmu_mode_enable();
+	lazy_mmu_mode_enable_with_ptes(src_mm, addr, end, src_pte);
 
 	do {
 		nr = 1;
@@ -1922,7 +1922,7 @@ static unsigned long zap_pte_range(struct mmu_gather *tlb,
 		return addr;
 
 	flush_tlb_batched_pending(mm);
-	lazy_mmu_mode_enable();
+	lazy_mmu_mode_enable_with_ptes(mm, addr, end, start_pte);
 	do {
 		bool any_skipped = false;
 
@@ -2919,7 +2919,7 @@ static int remap_pte_range(struct mm_struct *mm, pmd_t *pmd,
 	mapped_pte = pte = pte_alloc_map_lock(mm, pmd, addr, &ptl);
 	if (!pte)
 		return -ENOMEM;
-	lazy_mmu_mode_enable();
+	lazy_mmu_mode_enable_with_ptes(mm, addr, end, mapped_pte);
 	do {
 		BUG_ON(!pte_none(ptep_get(pte)));
 		if (!pfn_modify_allowed(pfn, prot)) {
@@ -3330,7 +3330,7 @@ static int apply_to_pte_range(struct mm_struct *mm, pmd_t *pmd,
 			return -EINVAL;
 	}
 
-	lazy_mmu_mode_enable();
+	lazy_mmu_mode_enable_with_ptes(mm, addr, end, mapped_pte);
 
 	if (fn) {
 		do {
diff --git a/mm/mprotect.c b/mm/mprotect.c
index 9cbf932b028c..3fc26418e837 100644
--- a/mm/mprotect.c
+++ b/mm/mprotect.c
@@ -337,7 +337,7 @@ static long change_pte_range(struct mmu_gather *tlb,
 		is_private_single_threaded = vma_is_single_threaded_private(vma);
 
 	flush_tlb_batched_pending(vma->vm_mm);
-	lazy_mmu_mode_enable();
+	lazy_mmu_mode_enable_with_ptes(vma->vm_mm, addr, end, pte);
 	do {
 		nr_ptes = 1;
 		oldpte = ptep_get(pte);
diff --git a/mm/mremap.c b/mm/mremap.c
index e9c8b1d05832..0dfe3de39ccc 100644
--- a/mm/mremap.c
+++ b/mm/mremap.c
@@ -260,7 +260,7 @@ static int move_ptes(struct pagetable_move_control *pmc,
 	if (new_ptl != old_ptl)
 		spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
 	flush_tlb_batched_pending(vma->vm_mm);
-	lazy_mmu_mode_enable();
+	lazy_mmu_mode_enable_with_ptes(mm, old_addr, old_end, old_ptep);
 
 	for (; old_addr < old_end; old_ptep += nr_ptes, old_addr += nr_ptes * PAGE_SIZE,
 		new_ptep += nr_ptes, new_addr += nr_ptes * PAGE_SIZE) {
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 1afca3568b9b..b5ed2b05771f 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -108,7 +108,7 @@ static int vmap_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
 	if (!pte)
 		return -ENOMEM;
 
-	lazy_mmu_mode_enable();
+	lazy_mmu_mode_enable_with_ptes(&init_mm, addr, end, pte);
 
 	do {
 		if (unlikely(!pte_none(ptep_get(pte)))) {
@@ -371,7 +371,7 @@ static void vunmap_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
 	unsigned long size = PAGE_SIZE;
 
 	pte = pte_offset_kernel(pmd, addr);
-	lazy_mmu_mode_enable();
+	lazy_mmu_mode_enable_with_ptes(&init_mm, addr, end, pte);
 
 	do {
 #ifdef CONFIG_HUGETLB_PAGE
@@ -538,7 +538,7 @@ static int vmap_pages_pte_range(pmd_t *pmd, unsigned long addr,
 	if (!pte)
 		return -ENOMEM;
 
-	lazy_mmu_mode_enable();
+	lazy_mmu_mode_enable_with_ptes(&init_mm, addr, end, pte);
 
 	do {
 		struct page *page = pages[*nr];
-- 
2.53.0