Whenever, we unbind (or change fence registers) on an object, we must
revoke any and all mmap_gtt using the previous bindings. Those user PTEs
point at the GGTT which know points into a new object, the wrong object.
Ergo, those PTEs must be cleared so that any user access provokes a new
page fault.
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Abdiel Janulgue <abdiel.janulgue@xxxxxxxxxxxxxxx>
---
.../drm/i915/gem/selftests/i915_gem_mman.c | 107 ++++++++++++++++++
1 file changed, 107 insertions(+)
diff --git a/drivers/gpu/drm/i915/gem/selftests/i915_gem_mman.c b/drivers/gpu/drm/i915/gem/selftests/i915_gem_mman.c
index 3c8f2297be86..687750388cd5 100644
--- a/drivers/gpu/drm/i915/gem/selftests/i915_gem_mman.c
+++ b/drivers/gpu/drm/i915/gem/selftests/i915_gem_mman.c
@@ -790,6 +790,112 @@ static int igt_mmap_gtt(void *arg)
return err;
}
+static int check_present_pte(pte_t *pte, unsigned long addr, void *data)
+{
+ if (!pte_present(*pte) || pte_none(*pte)) {
+ pr_err("missing PTE:%lx\n",
+ (addr - (unsigned long)data) >> PAGE_SHIFT);
+ return -EINVAL;
+ }
+
+ return 0;
+}
+
+static int check_absent_pte(pte_t *pte, unsigned long addr, void *data)
+{
+ if (pte_present(*pte) && !pte_none(*pte)) {
+ pr_err("present PTE:%lx; expected to be revoked\n",
+ (addr - (unsigned long)data) >> PAGE_SHIFT);
+ return -EINVAL;
+ }
+
+ return 0;
+}
+
+static int check_present(unsigned long addr, unsigned long len)
+{
+ return apply_to_page_range(current->mm, addr, len,
+ check_present_pte, (void *)addr);
+}
+
+static int check_absent(unsigned long addr, unsigned long len)
+{
+ return apply_to_page_range(current->mm, addr, len,
+ check_absent_pte, (void *)addr);
+}
+
+static int prefault_range(u64 start, u64 len)
+{
+ const char __user *addr, *end;
+ char __maybe_unused c;
+
+ addr = u64_to_user_ptr(start);
+ end = addr + len;
+
+ for (; addr < end; addr += PAGE_SIZE) {
+ int err = __get_user(c, addr);
+ if (err)
+ return err;
+ }
+
+ return __get_user(c, end - 1);
+}
+
+static int igt_mmap_gtt_revoke(void *arg)
+{
+ struct drm_i915_private *i915 = arg;
+ struct drm_i915_gem_object *obj;
+ unsigned long addr;
+ int err;
+
+ obj = i915_gem_object_create_internal(i915, SZ_4M);
+ if (IS_ERR(obj))
+ return PTR_ERR(obj);
+
+ err = create_mmap_offset(obj);
+ if (err)
+ goto out;
+
+ addr = igt_mmap_node(i915, &obj->base.vma_node,
+ 0, PROT_WRITE, MAP_SHARED);
+ if (IS_ERR_VALUE(addr)) {
+ err = addr;
+ goto out;
+ }
+
+ err = prefault_range(addr, obj->base.size);
+ if (err)
+ goto out_unmap;
+
+ GEM_BUG_ON(!atomic_read(&obj->bind_count));
+
+ err = check_present(addr, obj->base.size);
+ if (err)
+ goto out_unmap;
+
+ /*
+ * After unbinding the object from the GGTT, its address may be reused
+ * for other objects. Ergo we have to revoke the previous mmap PTE
+ * access as it no longer points to the same object.
+ */
+ err = i915_gem_object_unbind(obj, I915_GEM_OBJECT_UNBIND_ACTIVE);
+ if (err) {
+ pr_err("Failed to unbind object!\n");
+ goto out_unmap;
+ }
+ GEM_BUG_ON(atomic_read(&obj->bind_count));
+
+ err = check_absent(addr, obj->base.size);
+ if (err)
+ goto out_unmap;
+
+out_unmap:
+ vm_munmap(addr, obj->base.size);
+out:
+ i915_gem_object_put(obj);
+ return err;
+}
+
int i915_gem_mman_live_selftests(struct drm_i915_private *i915)
{
static const struct i915_subtest tests[] = {
@@ -797,6 +903,7 @@ int i915_gem_mman_live_selftests(struct drm_i915_private *i915)
SUBTEST(igt_smoke_tiling),
SUBTEST(igt_mmap_offset_exhaustion),
SUBTEST(igt_mmap_gtt),
+ SUBTEST(igt_mmap_gtt_revoke),
};
return i915_subtests(tests, i915);
--
2.24.0
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