Merge branch 'for-5.1/nfit/ars' into libnvdimm-for-next

Merge several updates to the ARS implementation. Highlights include:

* Support retrieval of short-ARS results if the ARS state is "requires
  continuation", and even if the "no_init_ars" module parameter is
  specified.
* Allow busy-polling of the kernel ARS state by allowing root to reset
  the exponential back-off timer.
* Filter potentially stale ARS results by tracking query-ARS relative to
  the previous start-ARS.

1 files changed, 51 insertions, 8 deletions

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_prime.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_prime.c
index 71913a18d142..a38e0fb4a6fe 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_prime.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_prime.c
@@ -38,6 +38,7 @@
 #include "amdgpu_gem.h"
 #include <drm/amdgpu_drm.h>
 #include <linux/dma-buf.h>
+#include <linux/dma-fence-array.h>
 
 /**
  * amdgpu_gem_prime_get_sg_table - &drm_driver.gem_prime_get_sg_table
@@ -187,6 +188,48 @@ error:
         return ERR_PTR(ret);
 }
 
+static int
+__reservation_object_make_exclusive(struct reservation_object *obj)
+{
+        struct dma_fence **fences;
+        unsigned int count;
+        int r;
+
+        if (!reservation_object_get_list(obj)) /* no shared fences to convert */
+                return 0;
+
+        r = reservation_object_get_fences_rcu(obj, NULL, &count, &fences);
+        if (r)
+                return r;
+
+        if (count == 0) {
+                /* Now that was unexpected. */
+        } else if (count == 1) {
+                reservation_object_add_excl_fence(obj, fences[0]);
+                dma_fence_put(fences[0]);
+                kfree(fences);
+        } else {
+                struct dma_fence_array *array;
+
+                array = dma_fence_array_create(count, fences,
+                                               dma_fence_context_alloc(1), 0,
+                                               false);
+                if (!array)
+                        goto err_fences_put;
+
+                reservation_object_add_excl_fence(obj, &array->base);
+                dma_fence_put(&array->base);
+        }
+
+        return 0;
+
+err_fences_put:
+        while (count--)
+                dma_fence_put(fences[count]);
+        kfree(fences);
+        return -ENOMEM;
+}
+
 /**
  * amdgpu_gem_map_attach - &dma_buf_ops.attach implementation
  * @dma_buf: Shared DMA buffer
@@ -218,16 +261,16 @@ static int amdgpu_gem_map_attach(struct dma_buf *dma_buf,
 
         if (attach->dev->driver != adev->dev->driver) {
                 /*
-                 * Wait for all shared fences to complete before we switch to future
-                 * use of exclusive fence on this prime shared bo.
+                 * We only create shared fences for internal use, but importers
+                 * of the dmabuf rely on exclusive fences for implicitly
+                 * tracking write hazards. As any of the current fences may
+                 * correspond to a write, we need to convert all existing
+                 * fences on the reservation object into a single exclusive
+                 * fence.
                  */
-                r = reservation_object_wait_timeout_rcu(bo->tbo.resv,
-                                                        true, false,
-                                                        MAX_SCHEDULE_TIMEOUT);
-                if (unlikely(r < 0)) {
-                        DRM_DEBUG_PRIME("Fence wait failed: %li\n", r);
+                r = __reservation_object_make_exclusive(bo->tbo.resv);
+                if (r)
                         goto error_unreserve;
-                }
         }
 
         /* pin buffer into GTT */