[PATCH 03/15] dma-buf & drm/amdgpu: remove dma_resv workaround

Christian König
2022-04-07T09:00:02Z

Rework the internals of the dma_resv object to allow adding more than one
write fence and remember for each fence what purpose it had.

This allows removing the workaround from amdgpu which used a container for
this instead.

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: amd-gfx@lists.freedesktop.org
---
drivers/dma-buf/dma-resv.c | 353 ++++++++------------
drivers/gpu/drm/amd/amdgpu/amdgpu_bo_list.h | 1 -
drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c | 53 +--
include/linux/dma-resv.h | 47 +--
4 files changed, 157 insertions(+), 297 deletions(-)

diff --git a/drivers/dma-buf/dma-resv.c b/drivers/dma-buf/dma-resv.c
index 543dae6566d2..378d47e1cfea 100644
--- a/drivers/dma-buf/dma-resv.c
+++ b/drivers/dma-buf/dma-resv.c
@@ -44,12 +44,12 @@
/**
* DOC: Reservation Object Overview
*
- * The reservation object provides a mechanism to manage shared and
- * exclusive fences associated with a buffer. A reservation object
- * can have attached one exclusive fence (normally associated with
- * write operations) or N shared fences (read operations). The RCU
- * mechanism is used to protect read access to fences from locked
- * write-side updates.
+ * The reservation object provides a mechanism to manage a container of
+ * dma_fence object associated with a resource. A reservation object
+ * can have any number of fences attaches to it. Each fence carries an usage
+ * parameter determining how the operation represented by the fence is using the
+ * resource. The RCU mechanism is used to protect read access to fences from
+ * locked write-side updates.
*
* See struct dma_resv for more details.
*/
@@ -57,39 +57,59 @@
DEFINE_WD_CLASS(reservation_ww_class);
EXPORT_SYMBOL(reservation_ww_class);

+/* Mask for the lower fence pointer bits */
+#define DMA_RESV_LIST_MASK 0x3
+
struct dma_resv_list {
struct rcu_head rcu;
- u32 shared_count, shared_max;
- struct dma_fence __rcu *shared[];
+ u32 num_fences, max_fences;
+ struct dma_fence __rcu *table[];
};

-/**
- * dma_resv_list_alloc - allocate fence list
- * @shared_max: number of fences we need space for
- *
+/* Extract the fence and usage flags from an RCU protected entry in the list. */
+static void dma_resv_list_entry(struct dma_resv_list *list, unsigned int index,
+ struct dma_resv *resv, struct dma_fence **fence,
+ enum dma_resv_usage *usage)
+{
+ long tmp;
+
+ tmp = (long)rcu_dereference_check(list->table[index],
+ resv ? dma_resv_held(resv) : true);
+ *fence = (struct dma_fence *)(tmp & ~DMA_RESV_LIST_MASK);
+ if (usage)
+ *usage = tmp & DMA_RESV_LIST_MASK;
+}
+
+/* Set the fence and usage flags at the specific index in the list. */
+static void dma_resv_list_set(struct dma_resv_list *list,
+ unsigned int index,
+ struct dma_fence *fence,
+ enum dma_resv_usage usage)
+{
+ long tmp = ((long)fence) | usage;
+
+ RCU_INIT_POINTER(list->table[index], (struct dma_fence *)tmp);
+}
+
+/*
* Allocate a new dma_resv_list and make sure to correctly initialize
- * shared_max.
+ * max_fences.
*/
-static struct dma_resv_list *dma_resv_list_alloc(unsigned int shared_max)
+static struct dma_resv_list *dma_resv_list_alloc(unsigned int max_fences)
{
struct dma_resv_list *list;

- list = kmalloc(struct_size(list, shared, shared_max), GFP_KERNEL);
+ list = kmalloc(struct_size(list, table, max_fences), GFP_KERNEL);
if (!list)
return NULL;

- list->shared_max = (ksize(list) - offsetof(typeof(*list), shared)) /
- sizeof(*list->shared);
+ list->max_fences = (ksize(list) - offsetof(typeof(*list), table)) /
+ sizeof(*list->table);

return list;
}

-/**
- * dma_resv_list_free - free fence list
- * @list: list to free
- *
- * Free a dma_resv_list and make sure to drop all references.
- */
+/* Free a dma_resv_list and make sure to drop all references. */
static void dma_resv_list_free(struct dma_resv_list *list)
{
unsigned int i;
@@ -97,9 +117,12 @@ static void dma_resv_list_free(struct dma_resv_list *list)
if (!list)
return;

- for (i = 0; i < list->shared_count; ++i)
- dma_fence_put(rcu_dereference_protected(list->shared[i], true));
+ for (i = 0; i < list->num_fences; ++i) {
+ struct dma_fence *fence;

+ dma_resv_list_entry(list, i, NULL, &fence, NULL);
+ dma_fence_put(fence);
+ }
kfree_rcu(list, rcu);
}

@@ -112,8 +135,7 @@ void dma_resv_init(struct dma_resv *obj)
ww_mutex_init(&obj->lock, &reservation_ww_class);
seqcount_ww_mutex_init(&obj->seq, &obj->lock);

- RCU_INIT_POINTER(obj->fence, NULL);
- RCU_INIT_POINTER(obj->fence_excl, NULL);
+ RCU_INIT_POINTER(obj->fences, NULL);
}
EXPORT_SYMBOL(dma_resv_init);

@@ -123,46 +145,32 @@ EXPORT_SYMBOL(dma_resv_init);
*/
void dma_resv_fini(struct dma_resv *obj)
{
- struct dma_resv_list *fobj;
- struct dma_fence *excl;
-
/*
* This object should be dead and all references must have
* been released to it, so no need to be protected with rcu.
*/
- excl = rcu_dereference_protected(obj->fence_excl, 1);
- if (excl)
- dma_fence_put(excl);
-
- fobj = rcu_dereference_protected(obj->fence, 1);
- dma_resv_list_free(fobj);
+ dma_resv_list_free(rcu_dereference_protected(obj->fences, true));
ww_mutex_destroy(&obj->lock);
}
EXPORT_SYMBOL(dma_resv_fini);

-static inline struct dma_fence *
-dma_resv_excl_fence(struct dma_resv *obj)
-{
- return rcu_dereference_check(obj->fence_excl, dma_resv_held(obj));
-}
-
-static inline struct dma_resv_list *dma_resv_shared_list(struct dma_resv *obj)
+/* Dereference the fences while ensuring RCU rules */
+static inline struct dma_resv_list *dma_resv_fences_list(struct dma_resv *obj)
{
- return rcu_dereference_check(obj->fence, dma_resv_held(obj));
+ return rcu_dereference_check(obj->fences, dma_resv_held(obj));
}

/**
- * dma_resv_reserve_fences - Reserve space to add shared fences to
- * a dma_resv.
+ * dma_resv_reserve_fences - Reserve space to add fences to a dma_resv object.
* @obj: reservation object
* @num_fences: number of fences we want to add
*
- * Should be called before dma_resv_add_shared_fence(). Must
- * be called with @obj locked through dma_resv_lock().
+ * Should be called before dma_resv_add_fence(). Must be called with @obj
+ * locked through dma_resv_lock().
*
* Note that the preallocated slots need to be re-reserved if @obj is unlocked
- * at any time before calling dma_resv_add_shared_fence(). This is validated
- * when CONFIG_DEBUG_MUTEXES is enabled.
+ * at any time before calling dma_resv_add_fence(). This is validated when
+ * CONFIG_DEBUG_MUTEXES is enabled.
*
* RETURNS
* Zero for success, or -errno
@@ -174,11 +182,11 @@ int dma_resv_reserve_fences(struct dma_resv *obj, unsigned int num_fences)

dma_resv_assert_held(obj);

- old = dma_resv_shared_list(obj);
- if (old && old->shared_max) {
- if ((old->shared_count + num_fences) <= old->shared_max)
+ old = dma_resv_fences_list(obj);
+ if (old && old->max_fences) {
+ if ((old->num_fences + num_fences) <= old->max_fences)
return 0;
- max = max(old->shared_count + num_fences, old->shared_max * 2);
+ max = max(old->num_fences + num_fences, old->max_fences * 2);
} else {
max = max(4ul, roundup_pow_of_two(num_fences));
}
@@ -193,27 +201,27 @@ int dma_resv_reserve_fences(struct dma_resv *obj, unsigned int num_fences)
* references from the old struct are carried over to
* the new.
*/
- for (i = 0, j = 0, k = max; i < (old ? old->shared_count : 0); ++i) {
+ for (i = 0, j = 0, k = max; i < (old ? old->num_fences : 0); ++i) {
+ enum dma_resv_usage usage;
struct dma_fence *fence;

- fence = rcu_dereference_protected(old->shared[i],
- dma_resv_held(obj));
+ dma_resv_list_entry(old, i, obj, &fence, &usage);
if (dma_fence_is_signaled(fence))
- RCU_INIT_POINTER(new->shared[--k], fence);
+ RCU_INIT_POINTER(new->table[--k], fence);
else
- RCU_INIT_POINTER(new->shared[j++], fence);
+ dma_resv_list_set(new, j++, fence, usage);
}
- new->shared_count = j;
+ new->num_fences = j;

/*
* We are not changing the effective set of fences here so can
* merely update the pointer to the new array; both existing
* readers and new readers will see exactly the same set of
- * active (unsignaled) shared fences. Individual fences and the
+ * active (unsignaled) fences. Individual fences and the
* old array are protected by RCU and so will not vanish under
* the gaze of the rcu_read_lock() readers.
*/
- rcu_assign_pointer(obj->fence, new);
+ rcu_assign_pointer(obj->fences, new);

if (!old)
return 0;
@@ -222,7 +230,7 @@ int dma_resv_reserve_fences(struct dma_resv *obj, unsigned int num_fences)
for (i = k; i < max; ++i) {
struct dma_fence *fence;

- fence = rcu_dereference_protected(new->shared[i],
+ fence = rcu_dereference_protected(new->table[i],
dma_resv_held(obj));
dma_fence_put(fence);
}
@@ -234,38 +242,39 @@ EXPORT_SYMBOL(dma_resv_reserve_fences);

#ifdef CONFIG_DEBUG_MUTEXES
/**
- * dma_resv_reset_max_fences - reset shared fences for debugging
+ * dma_resv_reset_max_fences - reset fences for debugging
* @obj: the dma_resv object to reset
*
- * Reset the number of pre-reserved shared slots to test that drivers do
+ * Reset the number of pre-reserved fence slots to test that drivers do
* correct slot allocation using dma_resv_reserve_fences(). See also
- * &dma_resv_list.shared_max.
+ * &dma_resv_list.max_fences.
*/
void dma_resv_reset_max_fences(struct dma_resv *obj)
{
- struct dma_resv_list *fences = dma_resv_shared_list(obj);
+ struct dma_resv_list *fences = dma_resv_fences_list(obj);

dma_resv_assert_held(obj);

- /* Test shared fence slot reservation */
+ /* Test fence slot reservation */
if (fences)
- fences->shared_max = fences->shared_count;
+ fences->max_fences = fences->num_fences;
}
EXPORT_SYMBOL(dma_resv_reset_max_fences);
#endif

/**
- * dma_resv_add_shared_fence - Add a fence to a shared slot
+ * dma_resv_add_fence - Add a fence to the dma_resv obj
* @obj: the reservation object
- * @fence: the shared fence to add
+ * @fence: the fence to add
+ * @usage: how the fence is used, see enum dma_resv_usage
*
- * Add a fence to a shared slot, @obj must be locked with dma_resv_lock(), and
+ * Add a fence to a slot, @obj must be locked with dma_resv_lock(), and
* dma_resv_reserve_fences() has been called.
*
* See also &dma_resv.fence for a discussion of the semantics.
*/
-static void dma_resv_add_shared_fence(struct dma_resv *obj,
- struct dma_fence *fence)
+void dma_resv_add_fence(struct dma_resv *obj, struct dma_fence *fence,
+ enum dma_resv_usage usage)
{
struct dma_resv_list *fobj;
struct dma_fence *old;
@@ -280,32 +289,33 @@ static void dma_resv_add_shared_fence(struct dma_resv *obj,
*/
WARN_ON(dma_fence_is_container(fence));

- fobj = dma_resv_shared_list(obj);
- count = fobj->shared_count;
+ fobj = dma_resv_fences_list(obj);
+ count = fobj->num_fences;

write_seqcount_begin(&obj->seq);

for (i = 0; i < count; ++i) {
+ enum dma_resv_usage old_usage;

- old = rcu_dereference_protected(fobj->shared[i],
- dma_resv_held(obj));
- if (old->context == fence->context ||
+ dma_resv_list_entry(fobj, i, obj, &old, &old_usage);
+ if ((old->context == fence->context && old_usage >= usage) ||
dma_fence_is_signaled(old))
goto replace;
}

- BUG_ON(fobj->shared_count >= fobj->shared_max);
+ BUG_ON(fobj->num_fences >= fobj->max_fences);
old = NULL;
count++;

replace:
- RCU_INIT_POINTER(fobj->shared[i], fence);
- /* pointer update must be visible before we extend the shared_count */
- smp_store_mb(fobj->shared_count, count);
+ dma_resv_list_set(fobj, i, fence, usage);
+ /* pointer update must be visible before we extend the num_fences */
+ smp_store_mb(fobj->num_fences, count);

write_seqcount_end(&obj->seq);
dma_fence_put(old);
}
+EXPORT_SYMBOL(dma_resv_add_fence);

/**
* dma_resv_replace_fences - replace fences in the dma_resv obj
@@ -326,128 +336,63 @@ void dma_resv_replace_fences(struct dma_resv *obj, uint64_t context,
enum dma_resv_usage usage)
{
struct dma_resv_list *list;
- struct dma_fence *old;
unsigned int i;

- /* Only readers supported for now */
- WARN_ON(usage != DMA_RESV_USAGE_READ);
-
dma_resv_assert_held(obj);

+ list = dma_resv_fences_list(obj);
write_seqcount_begin(&obj->seq);
+ for (i = 0; list && i < list->num_fences; ++i) {
+ struct dma_fence *old;

- old = dma_resv_excl_fence(obj);
- if (old->context == context) {
- RCU_INIT_POINTER(obj->fence_excl, dma_fence_get(replacement));
- dma_fence_put(old);
- }
-
- list = dma_resv_shared_list(obj);
- for (i = 0; list && i < list->shared_count; ++i) {
- old = rcu_dereference_protected(list->shared[i],
- dma_resv_held(obj));
+ dma_resv_list_entry(list, i, obj, &old, NULL);
if (old->context != context)
continue;

- rcu_assign_pointer(list->shared[i], dma_fence_get(replacement));
+ dma_resv_list_set(list, i, replacement, usage);
dma_fence_put(old);
}
-
write_seqcount_end(&obj->seq);
}
EXPORT_SYMBOL(dma_resv_replace_fences);

-/**
- * dma_resv_add_excl_fence - Add an exclusive fence.
- * @obj: the reservation object
- * @fence: the exclusive fence to add
- *
- * Add a fence to the exclusive slot. @obj must be locked with dma_resv_lock().
- * See also &dma_resv.fence_excl for a discussion of the semantics.
- */
-static void dma_resv_add_excl_fence(struct dma_resv *obj,
- struct dma_fence *fence)
-{
- struct dma_fence *old_fence = dma_resv_excl_fence(obj);
-
- dma_resv_assert_held(obj);
-
- dma_fence_get(fence);
-
- write_seqcount_begin(&obj->seq);
- /* write_seqcount_begin provides the necessary memory barrier */
- RCU_INIT_POINTER(obj->fence_excl, fence);
- write_seqcount_end(&obj->seq);
-
- dma_fence_put(old_fence);
-}
-
-/**
- * dma_resv_add_fence - Add a fence to the dma_resv obj
- * @obj: the reservation object
- * @fence: the fence to add
- * @usage: how the fence is used, see enum dma_resv_usage
- *
- * Add a fence to a slot, @obj must be locked with dma_resv_lock(), and
- * dma_resv_reserve_fences() has been called.
- *
- * See also &dma_resv.fence for a discussion of the semantics.
- */
-void dma_resv_add_fence(struct dma_resv *obj, struct dma_fence *fence,
- enum dma_resv_usage usage)
-{
- if (usage == DMA_RESV_USAGE_WRITE)
- dma_resv_add_excl_fence(obj, fence);
- else
- dma_resv_add_shared_fence(obj, fence);
-}
-EXPORT_SYMBOL(dma_resv_add_fence);
-
-/* Restart the iterator by initializing all the necessary fields, but not the
- * relation to the dma_resv object. */
+/* Restart the unlocked iteration by initializing the cursor object. */
static void dma_resv_iter_restart_unlocked(struct dma_resv_iter *cursor)
{
cursor->seq = read_seqcount_begin(&cursor->obj->seq);
- cursor->index = -1;
- cursor->shared_count = 0;
- if (cursor->usage >= DMA_RESV_USAGE_READ) {
- cursor->fences = dma_resv_shared_list(cursor->obj);
- if (cursor->fences)
- cursor->shared_count = cursor->fences->shared_count;
- } else {
- cursor->fences = NULL;
- }
+ cursor->index = 0;
+ cursor->num_fences = 0;
+ cursor->fences = dma_resv_fences_list(cursor->obj);
+ if (cursor->fences)
+ cursor->num_fences = cursor->fences->num_fences;
cursor->is_restarted = true;
}

/* Walk to the next not signaled fence and grab a reference to it */
static void dma_resv_iter_walk_unlocked(struct dma_resv_iter *cursor)
{
- struct dma_resv *obj = cursor->obj;
+ if (!cursor->fences)
+ return;

do {
/* Drop the reference from the previous round */
dma_fence_put(cursor->fence);

- if (cursor->index == -1) {
- cursor->fence = dma_resv_excl_fence(obj);
- cursor->index++;
- if (!cursor->fence)
- continue;
-
- } else if (!cursor->fences ||
- cursor->index >= cursor->shared_count) {
+ if (cursor->index >= cursor->num_fences) {
cursor->fence = NULL;
break;

- } else {
- struct dma_resv_list *fences = cursor->fences;
- unsigned int idx = cursor->index++;
-
- cursor->fence = rcu_dereference(fences->shared[idx]);
}
+
+ dma_resv_list_entry(cursor->fences, cursor->index++,
+ cursor->obj, &cursor->fence,
+ &cursor->fence_usage);
cursor->fence = dma_fence_get_rcu(cursor->fence);
- if (!cursor->fence || !dma_fence_is_signaled(cursor->fence))
+ if (!cursor->fence)
+ break;
+
+ if (!dma_fence_is_signaled(cursor->fence) &&
+ cursor->usage >= cursor->fence_usage)
break;
} while (true);
}
@@ -522,15 +467,9 @@ struct dma_fence *dma_resv_iter_first(struct dma_resv_iter *cursor)
dma_resv_assert_held(cursor->obj);

cursor->index = 0;
- if (cursor->usage >= DMA_RESV_USAGE_READ)
- cursor->fences = dma_resv_shared_list(cursor->obj);
- else
- cursor->fences = NULL;
-
- fence = dma_resv_excl_fence(cursor->obj);
- if (!fence)
- fence = dma_resv_iter_next(cursor);
+ cursor->fences = dma_resv_fences_list(cursor->obj);

+ fence = dma_resv_iter_next(cursor);
cursor->is_restarted = true;
return fence;
}
@@ -545,17 +484,22 @@ EXPORT_SYMBOL_GPL(dma_resv_iter_first);
*/
struct dma_fence *dma_resv_iter_next(struct dma_resv_iter *cursor)
{
- unsigned int idx;
+ struct dma_fence *fence;

dma_resv_assert_held(cursor->obj);

cursor->is_restarted = false;
- if (!cursor->fences || cursor->index >= cursor->fences->shared_count)
- return NULL;

- idx = cursor->index++;
- return rcu_dereference_protected(cursor->fences->shared[idx],
- dma_resv_held(cursor->obj));
+ do {
+ if (!cursor->fences ||
+ cursor->index >= cursor->fences->num_fences)
+ return NULL;
+
+ dma_resv_list_entry(cursor->fences, cursor->index++,
+ cursor->obj, &fence, &cursor->fence_usage);
+ } while (cursor->fence_usage > cursor->usage);
+
+ return fence;
}
EXPORT_SYMBOL_GPL(dma_resv_iter_next);

@@ -570,57 +514,43 @@ int dma_resv_copy_fences(struct dma_resv *dst, struct dma_resv *src)
{
struct dma_resv_iter cursor;
struct dma_resv_list *list;
- struct dma_fence *f, *excl;
+ struct dma_fence *f;

dma_resv_assert_held(dst);

list = NULL;
- excl = NULL;

dma_resv_iter_begin(&cursor, src, DMA_RESV_USAGE_READ);
dma_resv_for_each_fence_unlocked(&cursor, f) {

if (dma_resv_iter_is_restarted(&cursor)) {
dma_resv_list_free(list);
- dma_fence_put(excl);
-
- if (cursor.shared_count) {
- list = dma_resv_list_alloc(cursor.shared_count);
- if (!list) {
- dma_resv_iter_end(&cursor);
- return -ENOMEM;
- }

- list->shared_count = 0;
-
- } else {
- list = NULL;
+ list = dma_resv_list_alloc(cursor.num_fences);
+ if (!list) {
+ dma_resv_iter_end(&cursor);
+ return -ENOMEM;
}
- excl = NULL;
+ list->num_fences = 0;
}

dma_fence_get(f);
- if (dma_resv_iter_usage(&cursor) == DMA_RESV_USAGE_WRITE)
- excl = f;
- else
- RCU_INIT_POINTER(list->shared[list->shared_count++], f);
+ dma_resv_list_set(list, list->num_fences++, f,
+ dma_resv_iter_usage(&cursor));
}
dma_resv_iter_end(&cursor);

write_seqcount_begin(&dst->seq);
- excl = rcu_replace_pointer(dst->fence_excl, excl, dma_resv_held(dst));
- list = rcu_replace_pointer(dst->fence, list, dma_resv_held(dst));
+ list = rcu_replace_pointer(dst->fences, list, dma_resv_held(dst));
write_seqcount_end(&dst->seq);

dma_resv_list_free(list);
- dma_fence_put(excl);
-
return 0;
}
EXPORT_SYMBOL(dma_resv_copy_fences);

/**
- * dma_resv_get_fences - Get an object's shared and exclusive
+ * dma_resv_get_fences - Get an object's fences
* fences without update side lock held
* @obj: the reservation object
* @usage: controls which fences to include, see enum dma_resv_usage.
@@ -649,7 +579,7 @@ int dma_resv_get_fences(struct dma_resv *obj, enum dma_resv_usage usage,
while (*num_fences)
dma_fence_put((*fences)[--(*num_fences)]);

- count = cursor.shared_count + 1;
+ count = cursor.num_fences + 1;

/* Eventually re-allocate the array */
*fences = krealloc_array(*fences, count,
@@ -723,8 +653,7 @@ int dma_resv_get_singleton(struct dma_resv *obj, enum dma_resv_usage usage,
EXPORT_SYMBOL_GPL(dma_resv_get_singleton);

/**
- * dma_resv_wait_timeout - Wait on reservation's objects
- * shared and/or exclusive fences.
+ * dma_resv_wait_timeout - Wait on reservation's objects fences
* @obj: the reservation object
* @usage: controls which fences to include, see enum dma_resv_usage.
* @intr: if true, do interruptible wait
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_bo_list.h b/drivers/gpu/drm/amd/amdgpu/amdgpu_bo_list.h
index 044b41f0bfd9..529d52a204cf 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_bo_list.h
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_bo_list.h
@@ -34,7 +34,6 @@ struct amdgpu_fpriv;
struct amdgpu_bo_list_entry {
struct ttm_validate_buffer tv;
struct amdgpu_bo_va *bo_va;
- struct dma_fence_chain *chain;
uint32_t priority;
struct page **user_pages;
bool user_invalidated;
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
index 76fd916424d6..8de283997769 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
@@ -574,14 +574,6 @@ static int amdgpu_cs_parser_bos(struct amdgpu_cs_parser *p,
struct amdgpu_bo *bo = ttm_to_amdgpu_bo(e->tv.bo);

e->bo_va = amdgpu_vm_bo_find(vm, bo);
-
- if (bo->tbo.base.dma_buf && !amdgpu_bo_explicit_sync(bo)) {
- e->chain = dma_fence_chain_alloc();
- if (!e->chain) {
- r = -ENOMEM;
- goto error_validate;
- }
- }
}

/* Move fence waiting after getting reservation lock of
@@ -642,13 +634,8 @@ static int amdgpu_cs_parser_bos(struct amdgpu_cs_parser *p,
}

error_validate:
- if (r) {
- amdgpu_bo_list_for_each_entry(e, p->bo_list) {
- dma_fence_chain_free(e->chain);
- e->chain = NULL;
- }
+ if (r)
ttm_eu_backoff_reservation(&p->ticket, &p->validated);
- }
out:
return r;
}
@@ -688,17 +675,9 @@ static void amdgpu_cs_parser_fini(struct amdgpu_cs_parser *parser, int error,
{
unsigned i;

- if (error && backoff) {
- struct amdgpu_bo_list_entry *e;
-
- amdgpu_bo_list_for_each_entry(e, parser->bo_list) {
- dma_fence_chain_free(e->chain);
- e->chain = NULL;
- }
-
+ if (error && backoff)
ttm_eu_backoff_reservation(&parser->ticket,
&parser->validated);
- }

for (i = 0; i < parser->num_post_deps; i++) {
drm_syncobj_put(parser->post_deps[i].syncobj);
@@ -1272,31 +1251,9 @@ static int amdgpu_cs_submit(struct amdgpu_cs_parser *p,

amdgpu_vm_move_to_lru_tail(p->adev, &fpriv->vm);

- amdgpu_bo_list_for_each_entry(e, p->bo_list) {
- struct dma_resv *resv = e->tv.bo->base.resv;
- struct dma_fence_chain *chain = e->chain;
- struct dma_resv_iter cursor;
- struct dma_fence *fence;
-
- if (!chain)
- continue;
-
- /*
- * Temporary workaround dma_resv shortcommings by wrapping up
- * the submission in a dma_fence_chain and add it as exclusive
- * fence.
- *
- * TODO: Remove together with dma_resv rework.
- */
- dma_resv_for_each_fence(&cursor, resv,
- DMA_RESV_USAGE_WRITE,
- fence) {
- break;
- }
- dma_fence_chain_init(chain, fence, dma_fence_get(p->fence), 1);
- rcu_assign_pointer(resv->fence_excl, &chain->base);
- e->chain = NULL;
- }
+ /* Make sure all BOs are remembered as writers */
+ amdgpu_bo_list_for_each_entry(e, p->bo_list)
+ e->tv.num_shared = 0;

ttm_eu_fence_buffer_objects(&p->ticket, &p->validated, p->fence);
mutex_unlock(&p->adev->notifier_lock);
diff --git a/include/linux/dma-resv.h b/include/linux/dma-resv.h
index 98dc5234b487..7bb7e7edbb6f 100644
--- a/include/linux/dma-resv.h
+++ b/include/linux/dma-resv.h
@@ -99,8 +99,8 @@ static inline enum dma_resv_usage dma_resv_usage_rw(bool write)
/**
* struct dma_resv - a reservation object manages fences for a buffer
*
- * There are multiple uses for this, with sometimes slightly different rules in
- * how the fence slots are used.
+ * This is a container for dma_fence objects which needs to handle multiple use
+ * cases.
*
* One use is to synchronize cross-driver access to a struct dma_buf, either for
* dynamic buffer management or just to handle implicit synchronization between
@@ -130,47 +130,22 @@ struct dma_resv {
* @seq:
*
* Sequence count for managing RCU read-side synchronization, allows
- * read-only access to @fence_excl and @fence while ensuring we take a
- * consistent snapshot.
+ * read-only access to @fences while ensuring we take a consistent
+ * snapshot.
*/
seqcount_ww_mutex_t seq;

/**
- * @fence_excl:
+ * @fences:
*
- * The exclusive fence, if there is one currently.
+ * Array of fences which where added to the dma_resv object
*
- * To guarantee that no fences are lost, this new fence must signal
- * only after the previous exclusive fence has signalled. If
- * semantically only a new access is added without actually treating the
- * previous one as a dependency the exclusive fences can be strung
- * together using struct dma_fence_chain.
- *
- * Note that actual semantics of what an exclusive or shared fence mean
- * is defined by the user, for reservation objects shared across drivers
- * see &dma_buf.resv.
- */
- struct dma_fence __rcu *fence_excl;
-
- /**
- * @fence:
- *
- * List of current shared fences.
- *
- * There are no ordering constraints of shared fences against the
- * exclusive fence slot. If a waiter needs to wait for all access, it
- * has to wait for both sets of fences to signal.
- *
- * A new fence is added by calling dma_resv_add_shared_fence(). Since
- * this often needs to be done past the point of no return in command
+ * A new fence is added by calling dma_resv_add_fence(). Since this
+ * often needs to be done past the point of no return in command
* submission it cannot fail, and therefore sufficient slots need to be
* reserved by calling dma_resv_reserve_fences().
- *
- * Note that actual semantics of what an exclusive or shared fence mean
- * is defined by the user, for reservation objects shared across drivers
- * see &dma_buf.resv.
*/
- struct dma_resv_list __rcu *fence;
+ struct dma_resv_list __rcu *fences;
};

/**
@@ -207,8 +182,8 @@ struct dma_resv_iter {
/** @fences: the shared fences; private, *MUST* not dereference */
struct dma_resv_list *fences;

- /** @shared_count: number of shared fences */
- unsigned int shared_count;
+ /** @num_fences: number of fences */
+ unsigned int num_fences;

/** @is_restarted: true if this is the first returned fence */
bool is_restarted;
--
2.25.1