drm/i915/gem: Use a single chained reloc batches for a single execbuf

As we can now keep chaining together a relocation batch to process any
number of relocations, we can keep building that relocation batch for
all of the target vma. This avoiding emitting a new request into the
ring for each target, consuming precious ring space and a potential
stall.

v2: Propagate the failure from submitting the relocation batch.

Testcase: igt/gem_exec_reloc/basic-wide-active
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200501192945.22215-2-chris@chris-wilson.co.uk

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
index 0411618..3c01c41 100644 (file)
--- a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
@@ -268,6 +268,7 @@ struct i915_execbuffer {
                bool has_fence : 1;
                bool needs_unfenced : 1;
 
+               struct i915_vma *target;
                struct i915_request *rq;
                struct i915_vma *rq_vma;
                u32 *rq_cmd;
@@ -1051,14 +1052,14 @@ static unsigned int reloc_bb_flags(const struct reloc_cache *cache)
        return cache->gen > 5 ? 0 : I915_DISPATCH_SECURE;
 }
 
-static void reloc_gpu_flush(struct reloc_cache *cache)
+static int reloc_gpu_flush(struct reloc_cache *cache)
 {
        struct i915_request *rq;
        int err;
 
        rq = fetch_and_zero(&cache->rq);
        if (!rq)
-               return;
+               return 0;
 
        if (cache->rq_vma) {
                struct drm_i915_gem_object *obj = cache->rq_vma->obj;
@@ -1084,15 +1085,14 @@ static void reloc_gpu_flush(struct reloc_cache *cache)
 
        intel_gt_chipset_flush(rq->engine->gt);
        i915_request_add(rq);
+
+       return err;
 }
 
 static void reloc_cache_reset(struct reloc_cache *cache)
 {
        void *vaddr;
 
-       if (cache->rq)
-               reloc_gpu_flush(cache);
-
        if (!cache->vaddr)
                return;
 
@@ -1285,7 +1285,6 @@ static int reloc_move_to_gpu(struct i915_request *rq, struct i915_vma *vma)
 }
 
 static int __reloc_gpu_alloc(struct i915_execbuffer *eb,
-                            struct i915_vma *vma,
                             unsigned int len)
 {
        struct reloc_cache *cache = &eb->reloc_cache;
@@ -1308,7 +1307,7 @@ static int __reloc_gpu_alloc(struct i915_execbuffer *eb,
                goto out_pool;
        }
 
-       batch = i915_vma_instance(pool->obj, vma->vm, NULL);
+       batch = i915_vma_instance(pool->obj, eb->context->vm, NULL);
        if (IS_ERR(batch)) {
                err = PTR_ERR(batch);
                goto err_unmap;
@@ -1328,10 +1327,6 @@ static int __reloc_gpu_alloc(struct i915_execbuffer *eb,
        if (err)
                goto err_request;
 
-       err = reloc_move_to_gpu(rq, vma);
-       if (err)
-               goto err_request;
-
        i915_vma_lock(batch);
        err = i915_request_await_object(rq, batch->obj, false);
        if (err == 0)
@@ -1376,11 +1371,21 @@ static u32 *reloc_gpu(struct i915_execbuffer *eb,
                if (!intel_engine_can_store_dword(eb->engine))
                        return ERR_PTR(-ENODEV);
 
-               err = __reloc_gpu_alloc(eb, vma, len);
+               err = __reloc_gpu_alloc(eb, len);
                if (unlikely(err))
                        return ERR_PTR(err);
        }
 
+       if (vma != cache->target) {
+               err = reloc_move_to_gpu(cache->rq, vma);
+               if (unlikely(err)) {
+                       i915_request_set_error_once(cache->rq, err);
+                       return ERR_PTR(err);
+               }
+
+               cache->target = vma;
+       }
+
        if (unlikely(cache->rq_size + len >
                     PAGE_SIZE / sizeof(u32) - RELOC_TAIL)) {
                err = reloc_gpu_chain(cache);
@@ -1692,15 +1697,20 @@ static int eb_relocate(struct i915_execbuffer *eb)
        /* The objects are in their final locations, apply the relocations. */
        if (eb->args->flags & __EXEC_HAS_RELOC) {
                struct eb_vma *ev;
+               int flush;
 
                list_for_each_entry(ev, &eb->relocs, reloc_link) {
                        err = eb_relocate_vma(eb, ev);
                        if (err)
-                               return err;
+                               break;
                }
+
+               flush = reloc_gpu_flush(&eb->reloc_cache);
+               if (!err)
+                       err = flush;
        }
 
-       return 0;
+       return err;
 }
 
 static int eb_move_to_gpu(struct i915_execbuffer *eb)