drm/i915/gem: Ignore readonly failures when updating relocs

If the user passes in a readonly reloc[], by the time we notice we have
already committed to modifying the execobjects, or have indeed done so
already. Reporting the failure just compounds the issue as we have no
second pass to fall back to anymore.

"Be damned if you do, and damned if you don't."

Testcase: igt/gem_exec_reloc/readonly
Fixes: 7dc8f1143778 ("drm/i915/gem: Drop relocation slowpath")
References: fddcd00a49e9 ("drm/i915: Force the slow path after a user-write error")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Matthew Auld <matthew.auld@intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Reviewed-by: Andi Shyti <andi.shyti@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200331162150.3635-1-chris@chris-wilson.co.uk
(cherry picked from commit 97a37c919f6262fe75afc4a4eb838093bf18b032)
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
index 36d069504836efdde43d0d29a8f8966e8cee8ef6..cb2c0a64f8b93ec73a3e8d1665be5847100063e4 100644 (file)
--- a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
@@ -1477,10 +1477,8 @@ static int eb_relocate_vma(struct i915_execbuffer *eb, struct eb_vma *ev)
                                 * can read from this userspace address.
                                 */
                                offset = gen8_canonical_addr(offset & ~UPDATE);
-                               if (unlikely(__put_user(offset, &urelocs[r-stack].presumed_offset))) {
-                                       remain = -EFAULT;
-                                       goto out;
-                               }
+                               __put_user(offset,
+                                          &urelocs[r - stack].presumed_offset);
                        }
                } while (r++, --count);
                urelocs += ARRAY_SIZE(stack);