1 files changed, 11 insertions, 4 deletions

diff --git a/drivers/gpu/nvgpu/common/mm/pd_cache.c b/drivers/gpu/nvgpu/common/mm/pd_cache.c
index a5b3d134..8f7003e5 100644
--- a/drivers/gpu/nvgpu/common/mm/pd_cache.c
+++ b/drivers/gpu/nvgpu/common/mm/pd_cache.c
@@ -423,12 +423,19 @@ static void nvgpu_pd_cache_do_free(struct gk20a *g,
                  * this just re-adds it.
                  *
                  * Since the memory used for the entries is still mapped, if
-                 * igpu make sure the entries are invalidated so that the hw
-                 * doesn't accidentally try to prefetch non-existent fb memory.
+                 * iommu is being used,  make sure PTE entries in particular
+                 * are invalidated so that the hw doesn't accidentally try to
+                 * prefetch non-existent fb memory.
                  *
-                 * TBD: what about dgpu? (Not supported in Drive 5.0)
+                 * Notes:
+                 *   - The check for NVGPU_PD_CACHE_SIZE > PAGE_SIZE effectively
+                 *     determines whether PTE entries use the cache.
+                 *   - In the case where PTE entries ues the cache, we also
+                 *     end up invalidating the PDE entries, but that's a minor
+                 *     performance hit, as there are far fewer of those
+                 *     typically than there are PTE entries.
                  */
-                if (pd->mem->cpu_va != NULL) {
+                if (nvgpu_iommuable(g) && (NVGPU_PD_CACHE_SIZE > PAGE_SIZE)) {
                         memset((void *)((u64)pd->mem->cpu_va + pd->mem_offs), 0,
                                         pentry->pd_size);
                 }