drm/ttm, drm/amdgpu: Allow the driver some control over swapping

We are calling the eviction_valuable driver callback at eviction time to
determine whether we actually can evict a buffer object.
The upcoming i915 TTM backend needs the same functionality for swapout,
and that might actually be beneficial to other drivers as well.

Add an eviction_valuable call also in the swapout path. Try to keep the
current behaviour for all drivers by returning true if the buffer object
is already in the TTM_PL_SYSTEM placement. We change behaviour for the
case where a buffer object is in a TT backed placement when swapped out,
in which case the drivers normal eviction_valuable path is run.

Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Christian König <christian.koenig@amd.com>
Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Acked-by: Christian König <christian.koenig@amd.com>
Link: https://lore.kernel.org/r/20210602083818.241793-8-thomas.hellstrom@linux.intel.com
Link: https://patchwork.freedesktop.org/patch/msgid/20210602083818.241793-8-thomas.hellstrom@linux.intel.com

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
index 53a8ab8ce2a70e1faf247e708b8bb63e61b9508a..ea26cb5072e33f9ed1d2ff14a4e82ed4c4e37df4 100644 (file)
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
@@ -1331,6 +1331,10 @@ static bool amdgpu_ttm_bo_eviction_valuable(struct ttm_buffer_object *bo,
        struct dma_fence *f;
        int i;
 
+       /* Swapout? */
+       if (bo->resource->mem_type == TTM_PL_SYSTEM)
+               return true;
+
        if (bo->type == ttm_bo_type_kernel &&
            !amdgpu_vm_evictable(ttm_to_amdgpu_bo(bo)))
                return false;

diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c
index c0ca28edd869076959857b468fc1a825ecfceb1e..08f8797eaa7ba1410ca2d0d3704050749bd818f5 100644 (file)
--- a/drivers/gpu/drm/ttm/ttm_bo.c
+++ b/drivers/gpu/drm/ttm/ttm_bo.c
@@ -538,6 +538,10 @@ out:
 bool ttm_bo_eviction_valuable(struct ttm_buffer_object *bo,
                              const struct ttm_place *place)
 {
+       dma_resv_assert_held(bo->base.resv);
+       if (bo->resource->mem_type == TTM_PL_SYSTEM)
+               return true;
+
        /* Don't evict this BO if it's outside of the
         * requested placement range
         */
@@ -560,7 +564,9 @@ EXPORT_SYMBOL(ttm_bo_eviction_valuable);
  * b. Otherwise, trylock it.
  */
 static bool ttm_bo_evict_swapout_allowable(struct ttm_buffer_object *bo,
-                       struct ttm_operation_ctx *ctx, bool *locked, bool *busy)
+                                          struct ttm_operation_ctx *ctx,
+                                          const struct ttm_place *place,
+                                          bool *locked, bool *busy)
 {
        bool ret = false;
 
@@ -578,6 +584,14 @@ static bool ttm_bo_evict_swapout_allowable(struct ttm_buffer_object *bo,
                        *busy = !ret;
        }
 
+       if (ret && place && !bo->bdev->funcs->eviction_valuable(bo, place)) {
+               ret = false;
+               if (*locked) {
+                       dma_resv_unlock(bo->base.resv);
+                       *locked = false;
+               }
+       }
+
        return ret;
 }
 
@@ -632,20 +646,14 @@ int ttm_mem_evict_first(struct ttm_device *bdev,
                list_for_each_entry(bo, &man->lru[i], lru) {
                        bool busy;
 
-                       if (!ttm_bo_evict_swapout_allowable(bo, ctx, &locked,
-                                                           &busy)) {
+                       if (!ttm_bo_evict_swapout_allowable(bo, ctx, place,
+                                                           &locked, &busy)) {
                                if (busy && !busy_bo && ticket !=
                                    dma_resv_locking_ctx(bo->base.resv))
                                        busy_bo = bo;
                                continue;
                        }
 
-                       if (place && !bdev->funcs->eviction_valuable(bo,
-                                                                     place)) {
-                               if (locked)
-                                       dma_resv_unlock(bo->base.resv);
-                               continue;
-                       }
                        if (!ttm_bo_get_unless_zero(bo)) {
                                if (locked)
                                        dma_resv_unlock(bo->base.resv);
@@ -1116,10 +1124,19 @@ EXPORT_SYMBOL(ttm_bo_wait);
 int ttm_bo_swapout(struct ttm_buffer_object *bo, struct ttm_operation_ctx *ctx,
                   gfp_t gfp_flags)
 {
+       struct ttm_place place;
        bool locked;
        int ret;
 
-       if (!ttm_bo_evict_swapout_allowable(bo, ctx, &locked, NULL))
+       /*
+        * While the bo may already reside in SYSTEM placement, set
+        * SYSTEM as new placement to cover also the move further below.
+        * The driver may use the fact that we're moving from SYSTEM
+        * as an indication that we're about to swap out.
+        */
+       memset(&place, 0, sizeof(place));
+       place.mem_type = TTM_PL_SYSTEM;
+       if (!ttm_bo_evict_swapout_allowable(bo, ctx, &place, &locked, NULL))
                return -EBUSY;
 
        if (!ttm_bo_get_unless_zero(bo)) {
@@ -1144,13 +1161,9 @@ int ttm_bo_swapout(struct ttm_buffer_object *bo, struct ttm_operation_ctx *ctx,
        if (bo->resource->mem_type != TTM_PL_SYSTEM) {
                struct ttm_operation_ctx ctx = { false, false };
                struct ttm_resource *evict_mem;
-               struct ttm_place place, hop;
+               struct ttm_place hop;
 
-               memset(&place, 0, sizeof(place));
                memset(&hop, 0, sizeof(hop));
-
-               place.mem_type = TTM_PL_SYSTEM;
-
                ret = ttm_resource_alloc(bo, &place, &evict_mem);
                if (unlikely(ret))
                        goto out;
@@ -1178,7 +1191,8 @@ int ttm_bo_swapout(struct ttm_buffer_object *bo, struct ttm_operation_ctx *ctx,
        if (bo->bdev->funcs->swap_notify)
                bo->bdev->funcs->swap_notify(bo);
 
-       ret = ttm_tt_swapout(bo->bdev, bo->ttm, gfp_flags);
+       if (ttm_tt_is_populated(bo->ttm))
+               ret = ttm_tt_swapout(bo->bdev, bo->ttm, gfp_flags);
 out:
 
        /*