From f0d34fcaa9e2fb1e699fe09e41198834d640ac6f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Christian=20K=C3=B6nig?= <christian.koenig@amd.com>
Date: Tue, 21 Dec 2021 21:00:48 +0100
Subject: drm/i915: remove questionable fence optimization during copy
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Git-commit: 33654ef470a97f9fcb19abc7e7ef660ea37e3aed
Patch-mainline: v5.17-rc1
References: jsc#PED-1166 jsc#PED-1168 jsc#PED-1170 jsc#PED-1218 jsc#PED-1220 jsc#PED-1222 jsc#PED-1223 jsc#PED-1225
First of all as discussed multiple times now kernel copies *must* always
wait for all fences in a BO before actually doing the copy. This is
mandatory.
Additional to that drop the handling when there can't be a shared slot
allocated on the source BO and just properly return an error code.
Otherwise this code path would only be tested under out of memory
conditions.
Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20211221200050.436316-3-thomas.hellstrom@linux.intel.com
Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Acked-by: Patrik Jakobsson <pjakobsson@suse.de>
---
drivers/gpu/drm/i915/gem/i915_gem_ttm_move.c | 43 +++++++-------------
1 file changed, 14 insertions(+), 29 deletions(-)
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_ttm_move.c b/drivers/gpu/drm/i915/gem/i915_gem_ttm_move.c
index 62a6fd2d127d..5dbaccf3f201 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_ttm_move.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_ttm_move.c
@@ -195,19 +195,14 @@ static int i915_deps_add_dependency(struct i915_deps *deps,
}
static int i915_deps_add_resv(struct i915_deps *deps, struct dma_resv *resv,
- bool all, const bool no_excl,
const struct ttm_operation_ctx *ctx)
{
struct dma_resv_iter iter;
struct dma_fence *fence;
+ int ret;
dma_resv_assert_held(resv);
- dma_resv_for_each_fence(&iter, resv, all, fence) {
- int ret;
-
- if (no_excl && dma_resv_iter_is_exclusive(&iter))
- continue;
-
+ dma_resv_for_each_fence(&iter, resv, true, fence) {
ret = i915_deps_add_dependency(deps, fence, ctx);
if (ret)
return ret;
@@ -634,11 +629,7 @@ prev_deps(struct ttm_buffer_object *bo, struct ttm_operation_ctx *ctx,
ret = i915_deps_add_dependency(deps, bo->moving, ctx);
if (!ret)
- /*
- * TODO: Only await excl fence here, and shared fences before
- * signaling the migration fence.
- */
- ret = i915_deps_add_resv(deps, bo->base.resv, true, false, ctx);
+ ret = i915_deps_add_resv(deps, bo->base.resv, ctx);
return ret;
}
@@ -768,22 +759,21 @@ int i915_gem_obj_copy_ttm(struct drm_i915_gem_object *dst,
struct i915_refct_sgt *dst_rsgt;
struct dma_fence *copy_fence;
struct i915_deps deps;
- int ret, shared_err;
+ int ret;
assert_object_held(dst);
assert_object_held(src);
i915_deps_init(&deps, GFP_KERNEL | __GFP_NORETRY | __GFP_NOWARN);
- /*
- * We plan to add a shared fence only for the source. If that
- * fails, we await all source fences before commencing
- * the copy instead of only the exclusive.
- */
- shared_err = dma_resv_reserve_shared(src_bo->base.resv, 1);
- ret = i915_deps_add_resv(&deps, dst_bo->base.resv, true, false, &ctx);
- if (!ret)
- ret = i915_deps_add_resv(&deps, src_bo->base.resv,
- !!shared_err, false, &ctx);
+ ret = dma_resv_reserve_shared(src_bo->base.resv, 1);
+ if (ret)
+ return ret;
+
+ ret = i915_deps_add_resv(&deps, dst_bo->base.resv, &ctx);
+ if (ret)
+ return ret;
+
+ ret = i915_deps_add_resv(&deps, src_bo->base.resv, &ctx);
if (ret)
return ret;
@@ -798,12 +788,7 @@ int i915_gem_obj_copy_ttm(struct drm_i915_gem_object *dst,
return PTR_ERR_OR_ZERO(copy_fence);
dma_resv_add_excl_fence(dst_bo->base.resv, copy_fence);
-
- /* If we failed to reserve a shared slot, add an exclusive fence */
- if (shared_err)
- dma_resv_add_excl_fence(src_bo->base.resv, copy_fence);
- else
- dma_resv_add_shared_fence(src_bo->base.resv, copy_fence);
+ dma_resv_add_shared_fence(src_bo->base.resv, copy_fence);
dma_fence_put(copy_fence);
--
2.38.1