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path: root/drivers/xen/gntdev.c
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Diffstat (limited to 'drivers/xen/gntdev.c')
-rw-r--r--drivers/xen/gntdev.c34
1 files changed, 34 insertions, 0 deletions
diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c
index bccc54a..20c6577 100644
--- a/drivers/xen/gntdev.c
+++ b/drivers/xen/gntdev.c
@@ -244,6 +244,14 @@ static int find_grant_ptes(pte_t *pte, pgtable_t token,
BUG_ON(pgnr >= map->count);
pte_maddr = arbitrary_virt_to_machine(pte).maddr;
+ /*
+ * Set the PTE as special to force get_user_pages_fast() fall
+ * back to the slow path. If this is not supported as part of
+ * the grant map, it will be done afterwards.
+ */
+ if (xen_feature(XENFEAT_gnttab_map_avail_bits))
+ flags |= (1 << _GNTMAP_guest_avail0);
+
gnttab_set_map_op(&map->map_ops[pgnr], pte_maddr, flags,
map->grants[pgnr].ref,
map->grants[pgnr].domid);
@@ -252,6 +260,15 @@ static int find_grant_ptes(pte_t *pte, pgtable_t token,
return 0;
}
+#ifdef CONFIG_X86
+static int set_grant_ptes_as_special(pte_t *pte, pgtable_t token,
+ unsigned long addr, void *data)
+{
+ set_pte_at(current->mm, addr, pte, pte_mkspecial(*pte));
+ return 0;
+}
+#endif
+
static int map_grant_pages(struct grant_map *map)
{
int i, err = 0;
@@ -840,6 +857,23 @@ static int gntdev_mmap(struct file *flip, struct vm_area_struct *vma)
if (err)
goto out_put_map;
}
+ } else {
+#ifdef CONFIG_X86
+ /*
+ * If the PTEs were not made special by the grant map
+ * hypercall, do so here.
+ *
+ * This is racy since the mapping is already visible
+ * to userspace but userspace should be well-behaved
+ * enough to not touch it until the mmap() call
+ * returns.
+ */
+ if (!xen_feature(XENFEAT_gnttab_map_avail_bits)) {
+ apply_to_page_range(vma->vm_mm, vma->vm_start,
+ vma->vm_end - vma->vm_start,
+ set_grant_ptes_as_special, NULL);
+ }
+#endif
}
return 0;