drm/i915: fix i915 running as dom0 under Xen

Commit 920cf4194954ec ("drm/i915: Introduce an internal allocator for
disposable private objects") introduced a regression for the kernel
running as Xen dom0: when switching to graphics mode a GPU HANG
occurred.

Reason seems to be a missing adaption similar to that done in
commit 7453c549f5f648 ("swiotlb: Export swiotlb_max_segment to users")
to i915_gem_object_get_pages_internal().

So limit the maximum page order to be used according to the maximum
swiotlb segment size instead to the complete swiotlb size.

Fixes: 920cf4194954 ("drm/i915: Introduce an internal allocator for disposable private objects")
Signed-off-by: Juergen Gross <jgross@suse.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170202094711.939-1-jgross@suse.com
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Cc: Daniel Vetter <daniel.vetter@intel.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: intel-gfx@lists.freedesktop.org
Cc: <drm-intel-fixes@lists.freedesktop.org> # v4.10-rc1+
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
(cherry picked from commit 5584f1b1d73e9cc95092734c316e467c6c4468f9)
Signed-off-by: Jani Nikula <jani.nikula@intel.com>

diff --git a/drivers/gpu/drm/i915/i915_gem_internal.c b/drivers/gpu/drm/i915/i915_gem_internal.c
index 4b3ff3e5b911167557880228d5da44bb3d2616bf..d09c74973cb37a6c8d599c007ea4a53c0e0994e0 100644 (file)
--- a/drivers/gpu/drm/i915/i915_gem_internal.c
+++ b/drivers/gpu/drm/i915/i915_gem_internal.c
@@ -66,8 +66,16 @@ i915_gem_object_get_pages_internal(struct drm_i915_gem_object *obj)
 
        max_order = MAX_ORDER;
 #ifdef CONFIG_SWIOTLB
-       if (swiotlb_nr_tbl()) /* minimum max swiotlb size is IO_TLB_SEGSIZE */
-               max_order = min(max_order, ilog2(IO_TLB_SEGPAGES));
+       if (swiotlb_nr_tbl()) {
+               unsigned int max_segment;
+
+               max_segment = swiotlb_max_segment();
+               if (max_segment) {
+                       max_segment = max_t(unsigned int, max_segment,
+                                           PAGE_SIZE) >> PAGE_SHIFT;
+                       max_order = min(max_order, ilog2(max_segment));
+               }
+       }
 #endif
 
        gfp = GFP_KERNEL | __GFP_HIGHMEM | __GFP_RECLAIMABLE;