drm/i915/gem: Prevent using pgprot_writecombine() if PAT is not supported

[linux-2.6-microblaze.git] / drivers / gpu / drm / i915 / gem / i915_gem_pages.c

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_pages.c b/drivers/gpu/drm/i915/gem/i915_gem_pages.c
index e8a0837..d6eeefa 100644 (file)
--- a/drivers/gpu/drm/i915/gem/i915_gem_pages.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_pages.c
@@ -254,9 +254,35 @@ static void *i915_gem_object_map(struct drm_i915_gem_object *obj,
        if (!i915_gem_object_has_struct_page(obj) && type != I915_MAP_WC)
                return NULL;
 
+       if (GEM_WARN_ON(type == I915_MAP_WC &&
+                       !static_cpu_has(X86_FEATURE_PAT)))
+               return NULL;
+
        /* A single page can always be kmapped */
-       if (n_pte == 1 && type == I915_MAP_WB)
-               return kmap(sg_page(sgt->sgl));
+       if (n_pte == 1 && type == I915_MAP_WB) {
+               struct page *page = sg_page(sgt->sgl);
+
+               /*
+                * On 32b, highmem using a finite set of indirect PTE (i.e.
+                * vmap) to provide virtual mappings of the high pages.
+                * As these are finite, map_new_virtual() must wait for some
+                * other kmap() to finish when it runs out. If we map a large
+                * number of objects, there is no method for it to tell us
+                * to release the mappings, and we deadlock.
+                *
+                * However, if we make an explicit vmap of the page, that
+                * uses a larger vmalloc arena, and also has the ability
+                * to tell us to release unwanted mappings. Most importantly,
+                * it will fail and propagate an error instead of waiting
+                * forever.
+                *
+                * So if the page is beyond the 32b boundary, make an explicit
+                * vmap. On 64b, this check will be optimised away as we can
+                * directly kmap any page on the system.
+                */
+               if (!PageHighMem(page))
+                       return kmap(page);
+       }
 
        mem = stack;
        if (n_pte > ARRAY_SIZE(stack)) {