uml: customize tlb.h

Customize the hooks in tlb.h to optimize TLB flushing some more.

Add start and end fields to tlb_gather_mmu, which are used to limit
the address space range scanned when a region is unmapped.

The interfaces which just free page tables, without actually changing
mappings, don't need to cause a TLB flush.

Signed-off-by: Jeff Dike <jdike@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 121 insertions, 1 deletions

diff --git a/include/asm-um/tlb.h b/include/asm-um/tlb.h
index c640033bc1fd..39fc475df6c9 100644
--- a/include/asm-um/tlb.h
+++ b/include/asm-um/tlb.h
@@ -1,6 +1,126 @@
 #ifndef __UM_TLB_H
 #define __UM_TLB_H
 
-#include <asm/arch/tlb.h>
+#include <linux/swap.h>
+#include <asm/percpu.h>
+#include <asm/pgalloc.h>
+#include <asm/tlbflush.h>
+
+#define tlb_start_vma(tlb, vma) do { } while (0)
+#define tlb_end_vma(tlb, vma) do { } while (0)
+#define tlb_flush(tlb) flush_tlb_mm((tlb)->mm)
+
+/* struct mmu_gather is an opaque type used by the mm code for passing around
+ * any data needed by arch specific code for tlb_remove_page.
+ */
+struct mmu_gather {
+        struct mm_struct        *mm;
+        unsigned int            need_flush; /* Really unmapped some ptes? */
+        unsigned long           start;
+        unsigned long           end;
+        unsigned int            fullmm; /* non-zero means full mm flush */
+};
+
+/* Users of the generic TLB shootdown code must declare this storage space. */
+DECLARE_PER_CPU(struct mmu_gather, mmu_gathers);
+
+static inline void __tlb_remove_tlb_entry(struct mmu_gather *tlb, pte_t *ptep,
+                                          unsigned long address)
+{
+        if (tlb->start > address)
+                tlb->start = address;
+        if (tlb->end < address + PAGE_SIZE)
+                tlb->end = address + PAGE_SIZE;
+}
+
+static inline void init_tlb_gather(struct mmu_gather *tlb)
+{
+        tlb->need_flush = 0;
+
+        tlb->start = TASK_SIZE;
+        tlb->end = 0;
+
+        if (tlb->fullmm) {
+                tlb->start = 0;
+                tlb->end = TASK_SIZE;
+        }
+}
+
+/* tlb_gather_mmu
+ *      Return a pointer to an initialized struct mmu_gather.
+ */
+static inline struct mmu_gather *
+tlb_gather_mmu(struct mm_struct *mm, unsigned int full_mm_flush)
+{
+        struct mmu_gather *tlb = &get_cpu_var(mmu_gathers);
+
+        tlb->mm = mm;
+        tlb->fullmm = full_mm_flush;
+
+        init_tlb_gather(tlb);
+
+        return tlb;
+}
+
+extern void flush_tlb_mm_range(struct mm_struct *mm, unsigned long start,
+                               unsigned long end);
+
+static inline void
+tlb_flush_mmu(struct mmu_gather *tlb, unsigned long start, unsigned long end)
+{
+        if (!tlb->need_flush)
+                return;
+
+        flush_tlb_mm_range(tlb->mm, tlb->start, tlb->end);
+        init_tlb_gather(tlb);
+}
+
+/* tlb_finish_mmu
+ *      Called at the end of the shootdown operation to free up any resources
+ *      that were required.
+ */
+static inline void
+tlb_finish_mmu(struct mmu_gather *tlb, unsigned long start, unsigned long end)
+{
+        tlb_flush_mmu(tlb, start, end);
+
+        /* keep the page table cache within bounds */
+        check_pgt_cache();
+
+        put_cpu_var(mmu_gathers);
+}
+
+/* tlb_remove_page
+ *      Must perform the equivalent to __free_pte(pte_get_and_clear(ptep)),
+ *      while handling the additional races in SMP caused by other CPUs
+ *      caching valid mappings in their TLBs.
+ */
+static inline void tlb_remove_page(struct mmu_gather *tlb, struct page *page)
+{
+        tlb->need_flush = 1;
+        free_page_and_swap_cache(page);
+        return;
+}
+
+/**
+ * tlb_remove_tlb_entry - remember a pte unmapping for later tlb invalidation.
+ *
+ * Record the fact that pte's were really umapped in ->need_flush, so we can
+ * later optimise away the tlb invalidate.   This helps when userspace is
+ * unmapping already-unmapped pages, which happens quite a lot.
+ */
+#define tlb_remove_tlb_entry(tlb, ptep, address)                \
+        do {                                                    \
+                tlb->need_flush = 1;                            \
+                __tlb_remove_tlb_entry(tlb, ptep, address);     \
+        } while (0)
+
+#define pte_free_tlb(tlb, ptep) __pte_free_tlb(tlb, ptep)
+
+#define pud_free_tlb(tlb, pudp) __pud_free_tlb(tlb, pudp)
+
+#define pmd_free_tlb(tlb, pmdp) __pmd_free_tlb(tlb, pmdp)
+
+#define tlb_migrate_finish(mm) do {} while (0)
 
 #endif