asm-generic/tlb: Track which levels of the page tables have been cleared

It is common for architectures with hugepage support to require only a
single TLB invalidation operation per hugepage during unmap(), rather than
iterating through the mapping at a PAGE_SIZE increment. Currently,
however, the level in the page table where the unmap() operation occurs
is not stored in the mmu_gather structure, therefore forcing
architectures to issue additional TLB invalidation operations or to give
up and over-invalidate by e.g. invalidating the entire TLB.

Ideally, we could add an interval rbtree to the mmu_gather structure,
which would allow us to associate the correct mapping granule with the
various sub-mappings within the range being invalidated. However, this
is costly in terms of book-keeping and memory management, so instead we
approximate by keeping track of the page table levels that are cleared
and provide a means to query the smallest granule required for invalidation.

Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

diff --git a/include/asm-generic/tlb.h b/include/asm-generic/tlb.h
index 2b444ad945667df02acfdb2ad215c34c30ee7ff0..9791e98122a06b895271cf12812dd8934fe597f6 100644 (file)
--- a/include/asm-generic/tlb.h
+++ b/include/asm-generic/tlb.h
@@ -116,6 +116,14 @@ struct mmu_gather {
         */
        unsigned int            freed_tables : 1;
 
+       /*
+        * at which levels have we cleared entries?
+        */
+       unsigned int            cleared_ptes : 1;
+       unsigned int            cleared_pmds : 1;
+       unsigned int            cleared_puds : 1;
+       unsigned int            cleared_p4ds : 1;
+
        struct mmu_gather_batch *active;
        struct mmu_gather_batch local;
        struct page             *__pages[MMU_GATHER_BUNDLE];
@@ -150,6 +158,10 @@ static inline void __tlb_reset_range(struct mmu_gather *tlb)
                tlb->end = 0;
        }
        tlb->freed_tables = 0;
+       tlb->cleared_ptes = 0;
+       tlb->cleared_pmds = 0;
+       tlb->cleared_puds = 0;
+       tlb->cleared_p4ds = 0;
 }
 
 static inline void tlb_flush_mmu_tlbonly(struct mmu_gather *tlb)
@@ -199,6 +211,25 @@ static inline void tlb_remove_check_page_size_change(struct mmu_gather *tlb,
 }
 #endif
 
+static inline unsigned long tlb_get_unmap_shift(struct mmu_gather *tlb)
+{
+       if (tlb->cleared_ptes)
+               return PAGE_SHIFT;
+       if (tlb->cleared_pmds)
+               return PMD_SHIFT;
+       if (tlb->cleared_puds)
+               return PUD_SHIFT;
+       if (tlb->cleared_p4ds)
+               return P4D_SHIFT;
+
+       return PAGE_SHIFT;
+}
+
+static inline unsigned long tlb_get_unmap_size(struct mmu_gather *tlb)
+{
+       return 1UL << tlb_get_unmap_shift(tlb);
+}
+
 /*
  * In the case of tlb vma handling, we can optimise these away in the
  * case where we're doing a full MM flush.  When we're doing a munmap,
@@ -232,13 +263,19 @@ static inline void tlb_remove_check_page_size_change(struct mmu_gather *tlb,
 #define tlb_remove_tlb_entry(tlb, ptep, address)               \
        do {                                                    \
                __tlb_adjust_range(tlb, address, PAGE_SIZE);    \
+               tlb->cleared_ptes = 1;                          \
                __tlb_remove_tlb_entry(tlb, ptep, address);     \
        } while (0)
 
-#define tlb_remove_huge_tlb_entry(h, tlb, ptep, address)            \
-       do {                                                         \
-               __tlb_adjust_range(tlb, address, huge_page_size(h)); \
-               __tlb_remove_tlb_entry(tlb, ptep, address);          \
+#define tlb_remove_huge_tlb_entry(h, tlb, ptep, address)       \
+       do {                                                    \
+               unsigned long _sz = huge_page_size(h);          \
+               __tlb_adjust_range(tlb, address, _sz);          \
+               if (_sz == PMD_SIZE)                            \
+                       tlb->cleared_pmds = 1;                  \
+               else if (_sz == PUD_SIZE)                       \
+                       tlb->cleared_puds = 1;                  \
+               __tlb_remove_tlb_entry(tlb, ptep, address);     \
        } while (0)
 
 /**
@@ -252,6 +289,7 @@ static inline void tlb_remove_check_page_size_change(struct mmu_gather *tlb,
 #define tlb_remove_pmd_tlb_entry(tlb, pmdp, address)                   \
        do {                                                            \
                __tlb_adjust_range(tlb, address, HPAGE_PMD_SIZE);       \
+               tlb->cleared_pmds = 1;                                  \
                __tlb_remove_pmd_tlb_entry(tlb, pmdp, address);         \
        } while (0)
 
@@ -266,6 +304,7 @@ static inline void tlb_remove_check_page_size_change(struct mmu_gather *tlb,
 #define tlb_remove_pud_tlb_entry(tlb, pudp, address)                   \
        do {                                                            \
                __tlb_adjust_range(tlb, address, HPAGE_PUD_SIZE);       \
+               tlb->cleared_puds = 1;                                  \
                __tlb_remove_pud_tlb_entry(tlb, pudp, address);         \
        } while (0)
 
@@ -291,7 +330,8 @@ static inline void tlb_remove_check_page_size_change(struct mmu_gather *tlb,
 #define pte_free_tlb(tlb, ptep, address)                       \
        do {                                                    \
                __tlb_adjust_range(tlb, address, PAGE_SIZE);    \
-               tlb->freed_tables = 1;                  \
+               tlb->freed_tables = 1;                          \
+               tlb->cleared_pmds = 1;                          \
                __pte_free_tlb(tlb, ptep, address);             \
        } while (0)
 #endif
@@ -300,7 +340,8 @@ static inline void tlb_remove_check_page_size_change(struct mmu_gather *tlb,
 #define pmd_free_tlb(tlb, pmdp, address)                       \
        do {                                                    \
                __tlb_adjust_range(tlb, address, PAGE_SIZE);    \
-               tlb->freed_tables = 1;                  \
+               tlb->freed_tables = 1;                          \
+               tlb->cleared_puds = 1;                          \
                __pmd_free_tlb(tlb, pmdp, address);             \
        } while (0)
 #endif
@@ -310,7 +351,8 @@ static inline void tlb_remove_check_page_size_change(struct mmu_gather *tlb,
 #define pud_free_tlb(tlb, pudp, address)                       \
        do {                                                    \
                __tlb_adjust_range(tlb, address, PAGE_SIZE);    \
-               tlb->freed_tables = 1;                  \
+               tlb->freed_tables = 1;                          \
+               tlb->cleared_p4ds = 1;                          \
                __pud_free_tlb(tlb, pudp, address);             \
        } while (0)
 #endif
@@ -321,7 +363,7 @@ static inline void tlb_remove_check_page_size_change(struct mmu_gather *tlb,
 #define p4d_free_tlb(tlb, pudp, address)                       \
        do {                                                    \
                __tlb_adjust_range(tlb, address, PAGE_SIZE);    \
-               tlb->freed_tables = 1;                  \
+               tlb->freed_tables = 1;                          \
                __p4d_free_tlb(tlb, pudp, address);             \
        } while (0)
 #endif

diff --git a/mm/memory.c b/mm/memory.c
index c467102a5cbc5de5ab2ea4dff740f2611c1124a4..9135f48e8d84180e8112e87b863d297a214ae2f3 100644 (file)
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -267,8 +267,10 @@ void arch_tlb_finish_mmu(struct mmu_gather *tlb,
 {
        struct mmu_gather_batch *batch, *next;
 
-       if (force)
+       if (force) {
+               __tlb_reset_range(tlb);
                __tlb_adjust_range(tlb, start, end - start);
+       }
 
        tlb_flush_mmu(tlb);