1 files changed, 23 insertions, 3 deletions
diff --git a/drivers/gpu/drm/drm_memory.c b/drivers/gpu/drm/drm_memory.c
index 40c4349cb939..132fef8ff1b6 100644
--- a/drivers/gpu/drm/drm_memory.c
+++ b/drivers/gpu/drm/drm_memory.c
@@ -35,6 +35,7 @@
 
 #include <linux/highmem.h>
 #include <linux/export.h>
+#include <xen/xen.h>
 #include <drm/drmP.h>
 #include "drm_legacy.h"
 
@@ -150,15 +151,34 @@ void drm_legacy_ioremapfree(struct drm_local_map *map, struct drm_device *dev)
 }
 EXPORT_SYMBOL(drm_legacy_ioremapfree);
 
-u64 drm_get_max_iomem(void)
+bool drm_need_swiotlb(int dma_bits)
 {
 	struct resource *tmp;
 	resource_size_t max_iomem = 0;
 
+	/*
+	 * Xen paravirtual hosts require swiotlb regardless of requested dma
+	 * transfer size.
+	 *
+	 * NOTE: Really, what it requires is use of the dma_alloc_coherent
+	 *       allocator used in ttm_dma_populate() instead of
+	 *       ttm_populate_and_map_pages(), which bounce buffers so much in
+	 *       Xen it leads to swiotlb buffer exhaustion.
+	 */
+	if (xen_pv_domain())
+		return true;
+
+	/*
+	 * Enforce dma_alloc_coherent when memory encryption is active as well
+	 * for the same reasons as for Xen paravirtual hosts.
+	 */
+	if (mem_encrypt_active())
+		return true;
+
 	for (tmp = iomem_resource.child; tmp; tmp = tmp->sibling) {
 		max_iomem = max(max_iomem,  tmp->end);
 	}
 
-	return max_iomem;
+	return max_iomem > ((u64)1 << dma_bits);
 }
-EXPORT_SYMBOL(drm_get_max_iomem);
+EXPORT_SYMBOL(drm_need_swiotlb);