When a shared context mapping is requested, a search of the other
vmas mapping the same object is searched. For simplicity, vmas
can only share context if the following is true:
- They both request shared context mapping
- The are at the same virtual address
- They are of the same size
In addition, a task is only allowed to have a single vma with shared
context.
Some of these contstraints can be relaxed at a later date. They
make the code simpler for now.
Signed-off-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
---
arch/sparc/include/asm/mmu_context_64.h | 1 +
arch/sparc/include/asm/page_64.h | 1 +
arch/sparc/mm/hugetlbpage.c | 78 ++++++++++++++++++++++++++++++++-
arch/sparc/mm/init_64.c | 19 ++++++++
mm/hugetlb.c | 9 ++++
5 files changed, 106 insertions(+), 2 deletions(-)
diff --git a/arch/sparc/include/asm/mmu_context_64.h b/arch/sparc/include/asm/mmu_context_64.h
index 0dc95cb5..46c2c7e 100644
--- a/arch/sparc/include/asm/mmu_context_64.h
+++ b/arch/sparc/include/asm/mmu_context_64.h
@@ -23,6 +23,7 @@ void get_new_mmu_shared_context(struct mm_struct *mm);
void put_shared_context(struct mm_struct *mm);
void set_mm_shared_ctx(struct mm_struct *mm, struct shared_mmu_ctx *ctx);
void destroy_shared_context(struct mm_struct *mm);
+void set_vma_shared_ctx(struct vm_area_struct *vma);
#endif
#ifdef CONFIG_SMP
void smp_new_mmu_context_version(void);
diff --git a/arch/sparc/include/asm/page_64.h b/arch/sparc/include/asm/page_64.h
index c1263fc..ccceb76 100644
--- a/arch/sparc/include/asm/page_64.h
+++ b/arch/sparc/include/asm/page_64.h
@@ -33,6 +33,7 @@
#if defined(CONFIG_HUGETLB_PAGE) || defined(CONFIG_TRANSPARENT_HUGEPAGE)
struct pt_regs;
void hugetlb_setup(struct pt_regs *regs);
+void hugetlb_shared_setup(struct pt_regs *regs);
#endif
#define WANT_PAGE_VIRTUAL
diff --git a/arch/sparc/mm/hugetlbpage.c b/arch/sparc/mm/hugetlbpage.c
index 2039d45..5681df6 100644
--- a/arch/sparc/mm/hugetlbpage.c
+++ b/arch/sparc/mm/hugetlbpage.c
@@ -127,6 +127,80 @@ hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
pgoff, flags);
}
+#if defined(CONFIG_SHARED_MMU_CTX)
+static bool huge_vma_can_share_ctx(struct vm_area_struct *vma,
+ struct vm_area_struct *tvma)
+{
+ /*
+ * Do not match unless there is an actual context value. It
+ * could be the case that tvma is a new mapping with VM_SHARED_CTX
+ * set, but still not associated with a shared context ID.
+ */
+ if (!vma_shared_ctx_val(tvma))
+ return false;
+
+ /*
+ * For simple functionality now, vmas must be exactly the same
+ */
+ if ((vma->vm_flags & VM_LOCKED_CLEAR_MASK) ==
+ (tvma->vm_flags & VM_LOCKED_CLEAR_MASK) &&
+ vma->vm_pgoff == tvma->vm_pgoff &&
+ vma->vm_start == tvma->vm_start &&
+ vma->vm_end == tvma->vm_end)
+ return true;
+
+ return false;
+}
+
+/*
+ * If vma is marked as desiring shared contexxt, search for a context to
+ * share. If no context found, assign one.
+ */
+void huge_get_shared_ctx(struct mm_struct *mm, unsigned long addr)
+{
+ struct vm_area_struct *vma = find_vma(mm, addr);
+ struct address_space *mapping = vma->vm_file->f_mapping;
+ pgoff_t idx = ((addr - vma->vm_start) >> PAGE_SHIFT) +
+ vma->vm_pgoff;
+ struct vm_area_struct *tvma;
+
+ /*
+ * FIXME
+ *
+ * For now limit a task to a single shared context mapping
+ */
+ if (!(vma->vm_flags & VM_SHARED_CTX) || vma_shared_ctx_val(vma) ||
+ mm_shared_ctx_val(mm))
+ return;
+
+ i_mmap_lock_write(mapping);
+ vma_interval_tree_foreach(tvma, &mapping->i_mmap, idx, idx) {
+ if (tvma == vma)
+ continue;
+
+ if (huge_vma_can_share_ctx(vma, tvma)) {
+ set_mm_shared_ctx(mm, tvma->vm_shared_mmu_ctx.ctx);
+ set_vma_shared_ctx(vma);
+ if (likely(mm_shared_ctx_val(mm))) {
+ load_secondary_context(mm);
+ /*
+ * What about multiple matches ?
+ */
+ break;
+ }
+ }
+ }
+
+ if (!mm_shared_ctx_val(mm)) {
+ get_new_mmu_shared_context(mm);
+ set_vma_shared_ctx(vma);
+ load_secondary_context(mm);
+ }
+
+ i_mmap_unlock_write(mapping);
+}
+#endif
+
pte_t *huge_pte_alloc(struct mm_struct *mm,
unsigned long addr, unsigned long sz)
{
@@ -164,7 +238,7 @@ void set_huge_pte_at(struct mm_struct *mm, unsigned long addr,
if (!pte_present(*ptep) && pte_present(entry)) {
#if defined(CONFIG_SHARED_MMU_CTX)
- if (pte_val(entry) | _PAGE_SHR_CTX_4V)
+ if (is_sharedctx_pte(entry))
mm->context.shared_hugetlb_pte_count++;
else
#endif
@@ -188,7 +262,7 @@ pte_t huge_ptep_get_and_clear(struct mm_struct *mm, unsigned long addr,
entry = *ptep;
if (pte_present(entry)) {
#if defined(CONFIG_SHARED_MMU_CTX)
- if (pte_val(entry) | _PAGE_SHR_CTX_4V)
+ if (is_sharedctx_pte(entry))
mm->context.shared_hugetlb_pte_count--;
else
#endif
diff --git a/arch/sparc/mm/init_64.c b/arch/sparc/mm/init_64.c
index 2b310e5..25ad5bd 100644
--- a/arch/sparc/mm/init_64.c
+++ b/arch/sparc/mm/init_64.c
@@ -813,6 +813,25 @@ void set_mm_shared_ctx(struct mm_struct *mm, struct shared_mmu_ctx *ctx)
atomic_inc(&ctx->refcount);
mm->context.shared_ctx = ctx;
}
+
+/*
+ * Set the shared context value in the vma to that in the mm.
+ *
+ *
+ * Note that we are called from mmap with mmap_sem held.
+ */
+void set_vma_shared_ctx(struct vm_area_struct *vma)
+{
+ struct mm_struct *mm = vma->vm_mm;
+
+ BUG_ON(vma->vm_shared_mmu_ctx.ctx);
+
+ if (!mm_shared_ctx_val(mm))
+ return;
+
+ atomic_inc(&mm->context.shared_ctx->refcount);
+ vma->vm_shared_mmu_ctx.ctx = mm->context.shared_ctx;
+}
#endif
static int numa_enabled = 1;
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 418bf01..3733ba1 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -3150,6 +3150,15 @@ static pte_t make_huge_pte(struct vm_area_struct *vma, struct page *page,
entry = pte_mkhuge(entry);
entry = arch_make_huge_pte(entry, vma, page, writable);
+#if defined(CONFIG_SHARED_MMU_CTX)
+ /*
+ * FIXME
+ * needs arch independent way of setting - perhaps arch_make_huge_pte
+ */
+ if (vma->vm_flags & VM_SHARED_CTX)
+ pte_val(entry) |= _PAGE_SHR_CTX_4V;
+#endif
+
return entry;
}
--
2.7.4
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