[PATCH 11/36] drm/amdgpu: track ring state associated with a fence
Alex Deucher
alexander.deucher at amd.com
Mon Jul 7 19:03:30 UTC 2025
We need to know the wptr and sequence number associated
with a fence so that we can re-emit the unprocessed state
after a ring reset. Pre-allocate storage space for
the ring buffer contents and add helpers to save off
and re-emit the unprocessed state so that it can be
re-emitted after the queue is reset.
Signed-off-by: Alex Deucher <alexander.deucher at amd.com>
---
drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c | 90 +++++++++++++++++++++++
drivers/gpu/drm/amd/amdgpu/amdgpu_ib.c | 15 +++-
drivers/gpu/drm/amd/amdgpu/amdgpu_job.c | 4 +-
drivers/gpu/drm/amd/amdgpu/amdgpu_ring.c | 67 +++++++++++++++++
drivers/gpu/drm/amd/amdgpu/amdgpu_ring.h | 18 +++++
drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c | 4 +
6 files changed, 195 insertions(+), 3 deletions(-)
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c
index 2d6b2b486baf7..3f2080aecd5a3 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c
@@ -120,6 +120,7 @@ int amdgpu_fence_emit(struct amdgpu_ring *ring, struct dma_fence **f,
am_fence = kzalloc(sizeof(*am_fence), GFP_KERNEL);
if (!am_fence)
return -ENOMEM;
+ am_fence->context = 0;
} else {
am_fence = af;
}
@@ -127,6 +128,7 @@ int amdgpu_fence_emit(struct amdgpu_ring *ring, struct dma_fence **f,
am_fence->ring = ring;
seq = ++ring->fence_drv.sync_seq;
+ am_fence->seq = seq;
if (af) {
dma_fence_init(fence, &amdgpu_job_fence_ops,
&ring->fence_drv.lock,
@@ -141,6 +143,7 @@ int amdgpu_fence_emit(struct amdgpu_ring *ring, struct dma_fence **f,
amdgpu_ring_emit_fence(ring, ring->fence_drv.gpu_addr,
seq, flags | AMDGPU_FENCE_FLAG_INT);
+ amdgpu_fence_save_wptr(fence);
pm_runtime_get_noresume(adev_to_drm(adev)->dev);
ptr = &ring->fence_drv.fences[seq & ring->fence_drv.num_fences_mask];
if (unlikely(rcu_dereference_protected(*ptr, 1))) {
@@ -253,6 +256,7 @@ bool amdgpu_fence_process(struct amdgpu_ring *ring)
do {
struct dma_fence *fence, **ptr;
+ struct amdgpu_fence *am_fence;
++last_seq;
last_seq &= drv->num_fences_mask;
@@ -265,6 +269,12 @@ bool amdgpu_fence_process(struct amdgpu_ring *ring)
if (!fence)
continue;
+ /* Save the wptr in the fence driver so we know what the last processed
+ * wptr was. This is required for re-emitting the ring state for
+ * queues that are reset but are not guilty and thus have no guilty fence.
+ */
+ am_fence = container_of(fence, struct amdgpu_fence, base);
+ drv->signalled_wptr = am_fence->wptr;
dma_fence_signal(fence);
dma_fence_put(fence);
pm_runtime_mark_last_busy(adev_to_drm(adev)->dev);
@@ -727,6 +737,86 @@ void amdgpu_fence_driver_force_completion(struct amdgpu_ring *ring)
amdgpu_fence_process(ring);
}
+
+/**
+ * Kernel queue reset handling
+ *
+ * The driver can reset individual queues for most engines, but those queues
+ * may contain work from multiple contexts. Resetting the queue will reset
+ * lose all of that state. In order to minimize the collateral damage, the
+ * driver will save the ring contents which are not associated with the guilty
+ * context prior to resetting the queue. After resetting the queue the queue
+ * contents from the other contexts is re-emitted to the rings so that it can
+ * be processed by the engine. To handle this, we save the queue's write
+ * pointer (wptr) in the fences associated with each context. If we get a
+ * queue timeout, we can then use the wptrs from the fences to determine
+ * which data needs to be saved out of the queue's ring buffer.
+ */
+
+/**
+ * amdgpu_fence_driver_guilty_force_completion - force signal of specified sequence
+ *
+ * @fence: fence of the ring to signal
+ *
+ */
+void amdgpu_fence_driver_guilty_force_completion(struct amdgpu_fence *fence)
+{
+ dma_fence_set_error(&fence->base, -ETIME);
+ amdgpu_fence_write(fence->ring, fence->seq);
+ amdgpu_fence_process(fence->ring);
+}
+
+void amdgpu_fence_save_wptr(struct dma_fence *fence)
+{
+ struct amdgpu_fence *am_fence = container_of(fence, struct amdgpu_fence, base);
+
+ am_fence->wptr = am_fence->ring->wptr;
+}
+
+static void amdgpu_ring_backup_unprocessed_command(struct amdgpu_ring *ring,
+ u64 start_wptr, u32 end_wptr)
+{
+ unsigned int first_idx = start_wptr & ring->buf_mask;
+ unsigned int last_idx = end_wptr & ring->buf_mask;
+ unsigned int i;
+
+ /* Backup the contents of the ring buffer. */
+ for (i = first_idx; i != last_idx; ++i, i &= ring->buf_mask)
+ ring->ring_backup[ring->ring_backup_entries_to_copy++] = ring->ring[i];
+}
+
+void amdgpu_ring_backup_unprocessed_commands(struct amdgpu_ring *ring,
+ struct amdgpu_fence *guilty_fence)
+{
+ struct dma_fence *unprocessed;
+ struct dma_fence __rcu **ptr;
+ struct amdgpu_fence *fence;
+ u64 wptr, i, seqno;
+
+ seqno = amdgpu_fence_read(ring);
+ wptr = ring->fence_drv.signalled_wptr;
+ ring->ring_backup_entries_to_copy = 0;
+
+ for (i = seqno + 1; i <= ring->fence_drv.sync_seq; ++i) {
+ ptr = &ring->fence_drv.fences[i & ring->fence_drv.num_fences_mask];
+ rcu_read_lock();
+ unprocessed = rcu_dereference(*ptr);
+
+ if (unprocessed && !dma_fence_is_signaled(unprocessed)) {
+ fence = container_of(unprocessed, struct amdgpu_fence, base);
+
+ /* save everything if the ring is not guilty, otherwise
+ * just save the content from other contexts.
+ */
+ if (!guilty_fence || (fence->context != guilty_fence->context))
+ amdgpu_ring_backup_unprocessed_command(ring, wptr,
+ fence->wptr);
+ wptr = fence->wptr;
+ }
+ rcu_read_unlock();
+ }
+}
+
/*
* Common fence implementation
*/
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ib.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ib.c
index 206b70acb29a0..7d9bcb72e8dd3 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ib.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ib.c
@@ -139,7 +139,6 @@ int amdgpu_ib_schedule(struct amdgpu_ring *ring, unsigned int num_ibs,
int vmid = AMDGPU_JOB_GET_VMID(job);
bool need_pipe_sync = false;
unsigned int cond_exec;
-
unsigned int i;
int r = 0;
@@ -156,6 +155,11 @@ int amdgpu_ib_schedule(struct amdgpu_ring *ring, unsigned int num_ibs,
gds_va = job->gds_va;
init_shadow = job->init_shadow;
af = &job->hw_fence;
+ /* Save the context of the job for reset handling.
+ * The driver needs this so it can skip the ring
+ * contents for guilty contexts.
+ */
+ af->context = job->base.s_fence ? job->base.s_fence->finished.context : 0;
} else {
vm = NULL;
fence_ctx = 0;
@@ -307,8 +311,17 @@ int amdgpu_ib_schedule(struct amdgpu_ring *ring, unsigned int num_ibs,
ring->hw_prio == AMDGPU_GFX_PIPE_PRIO_HIGH)
ring->funcs->emit_wave_limit(ring, false);
+ /* Save the wptr associated with this fence.
+ * This must be last for resets to work properly
+ * as we need to save the wptr associated with this
+ * fence so we know what rings contents to backup
+ * after we reset the queue.
+ */
+ amdgpu_fence_save_wptr(*f);
+
amdgpu_ring_ib_end(ring);
amdgpu_ring_commit(ring);
+
return 0;
}
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_job.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_job.c
index f0b7080dccb8d..45febdc2f3493 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_job.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_job.c
@@ -89,8 +89,8 @@ static enum drm_gpu_sched_stat amdgpu_job_timedout(struct drm_sched_job *s_job)
{
struct amdgpu_ring *ring = to_amdgpu_ring(s_job->sched);
struct amdgpu_job *job = to_amdgpu_job(s_job);
- struct amdgpu_task_info *ti;
struct amdgpu_device *adev = ring->adev;
+ struct amdgpu_task_info *ti;
int idx, r;
if (!drm_dev_enter(adev_to_drm(adev), &idx)) {
@@ -135,7 +135,7 @@ static enum drm_gpu_sched_stat amdgpu_job_timedout(struct drm_sched_job *s_job)
} else if (amdgpu_gpu_recovery && ring->funcs->reset) {
dev_err(adev->dev, "Starting %s ring reset\n",
s_job->sched->name);
- r = amdgpu_ring_reset(ring, job->vmid, NULL);
+ r = amdgpu_ring_reset(ring, job->vmid, &job->hw_fence);
if (!r) {
atomic_inc(&ring->adev->gpu_reset_counter);
dev_err(adev->dev, "Ring %s reset succeeded\n",
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.c
index 426834806fbf2..09d7681b7a754 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.c
@@ -99,6 +99,29 @@ int amdgpu_ring_alloc(struct amdgpu_ring *ring, unsigned int ndw)
return 0;
}
+/**
+ * amdgpu_ring_alloc_reemit - allocate space on the ring buffer for reemit
+ *
+ * @ring: amdgpu_ring structure holding ring information
+ * @ndw: number of dwords to allocate in the ring buffer
+ *
+ * Allocate @ndw dwords in the ring buffer (all asics).
+ * doesn't check the max_dw limit as we may be reemitting
+ * several submissions.
+ */
+static void amdgpu_ring_alloc_reemit(struct amdgpu_ring *ring, unsigned int ndw)
+{
+ /* Align requested size with padding so unlock_commit can
+ * pad safely */
+ ndw = (ndw + ring->funcs->align_mask) & ~ring->funcs->align_mask;
+
+ ring->count_dw = ndw;
+ ring->wptr_old = ring->wptr;
+
+ if (ring->funcs->begin_use)
+ ring->funcs->begin_use(ring);
+}
+
/** amdgpu_ring_insert_nop - insert NOP packets
*
* @ring: amdgpu_ring structure holding ring information
@@ -333,6 +356,12 @@ int amdgpu_ring_init(struct amdgpu_device *adev, struct amdgpu_ring *ring,
/* Initialize cached_rptr to 0 */
ring->cached_rptr = 0;
+ if (!ring->ring_backup) {
+ ring->ring_backup = kvzalloc(ring->ring_size, GFP_KERNEL);
+ if (!ring->ring_backup)
+ return -ENOMEM;
+ }
+
/* Allocate ring buffer */
if (ring->ring_obj == NULL) {
r = amdgpu_bo_create_kernel(adev, ring->ring_size + ring->funcs->extra_dw, PAGE_SIZE,
@@ -342,6 +371,7 @@ int amdgpu_ring_init(struct amdgpu_device *adev, struct amdgpu_ring *ring,
(void **)&ring->ring);
if (r) {
dev_err(adev->dev, "(%d) ring create failed\n", r);
+ kvfree(ring->ring_backup);
return r;
}
amdgpu_ring_clear_ring(ring);
@@ -385,6 +415,8 @@ void amdgpu_ring_fini(struct amdgpu_ring *ring)
amdgpu_bo_free_kernel(&ring->ring_obj,
&ring->gpu_addr,
(void **)&ring->ring);
+ kvfree(ring->ring_backup);
+ ring->ring_backup = NULL;
dma_fence_put(ring->vmid_wait);
ring->vmid_wait = NULL;
@@ -753,3 +785,38 @@ bool amdgpu_ring_sched_ready(struct amdgpu_ring *ring)
return true;
}
+
+void amdgpu_ring_reset_helper_begin(struct amdgpu_ring *ring,
+ struct amdgpu_fence *guilty_fence)
+{
+ /* Stop the scheduler to prevent anybody else from touching the ring buffer. */
+ drm_sched_wqueue_stop(&ring->sched);
+ /* back up the non-guilty commands */
+ amdgpu_ring_backup_unprocessed_commands(ring, guilty_fence);
+}
+
+int amdgpu_ring_reset_helper_end(struct amdgpu_ring *ring,
+ struct amdgpu_fence *guilty_fence)
+{
+ unsigned int i;
+ int r;
+
+ /* verify that the ring is functional */
+ r = amdgpu_ring_test_ring(ring);
+ if (r)
+ return r;
+
+ /* signal the fence of the bad job */
+ if (guilty_fence)
+ amdgpu_fence_driver_guilty_force_completion(guilty_fence);
+ /* Re-emit the non-guilty commands */
+ if (ring->ring_backup_entries_to_copy) {
+ amdgpu_ring_alloc_reemit(ring, ring->ring_backup_entries_to_copy);
+ for (i = 0; i < ring->ring_backup_entries_to_copy; i++)
+ amdgpu_ring_write(ring, ring->ring_backup[i]);
+ amdgpu_ring_commit(ring);
+ }
+ /* Start the scheduler again */
+ drm_sched_wqueue_start(&ring->sched);
+ return 0;
+}
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.h b/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.h
index 784ba2ec354c7..309e7bb6001bd 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.h
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.h
@@ -118,6 +118,7 @@ struct amdgpu_fence_driver {
/* sync_seq is protected by ring emission lock */
uint32_t sync_seq;
atomic_t last_seq;
+ u64 signalled_wptr;
bool initialized;
struct amdgpu_irq_src *irq_src;
unsigned irq_type;
@@ -141,6 +142,12 @@ struct amdgpu_fence {
/* RB, DMA, etc. */
struct amdgpu_ring *ring;
ktime_t start_timestamp;
+
+ /* wptr for the fence for resets */
+ u64 wptr;
+ /* fence context for resets */
+ u64 context;
+ uint32_t seq;
};
extern const struct drm_sched_backend_ops amdgpu_sched_ops;
@@ -148,6 +155,8 @@ extern const struct drm_sched_backend_ops amdgpu_sched_ops;
void amdgpu_fence_driver_clear_job_fences(struct amdgpu_ring *ring);
void amdgpu_fence_driver_set_error(struct amdgpu_ring *ring, int error);
void amdgpu_fence_driver_force_completion(struct amdgpu_ring *ring);
+void amdgpu_fence_driver_guilty_force_completion(struct amdgpu_fence *fence);
+void amdgpu_fence_save_wptr(struct dma_fence *fence);
int amdgpu_fence_driver_init_ring(struct amdgpu_ring *ring);
int amdgpu_fence_driver_start_ring(struct amdgpu_ring *ring,
@@ -284,6 +293,9 @@ struct amdgpu_ring {
struct amdgpu_bo *ring_obj;
uint32_t *ring;
+ /* backups for resets */
+ uint32_t *ring_backup;
+ unsigned int ring_backup_entries_to_copy;
unsigned rptr_offs;
u64 rptr_gpu_addr;
volatile u32 *rptr_cpu_addr;
@@ -550,4 +562,10 @@ int amdgpu_ib_pool_init(struct amdgpu_device *adev);
void amdgpu_ib_pool_fini(struct amdgpu_device *adev);
int amdgpu_ib_ring_tests(struct amdgpu_device *adev);
bool amdgpu_ring_sched_ready(struct amdgpu_ring *ring);
+void amdgpu_ring_backup_unprocessed_commands(struct amdgpu_ring *ring,
+ struct amdgpu_fence *guilty_fence);
+void amdgpu_ring_reset_helper_begin(struct amdgpu_ring *ring,
+ struct amdgpu_fence *guilty_fence);
+int amdgpu_ring_reset_helper_end(struct amdgpu_ring *ring,
+ struct amdgpu_fence *guilty_fence);
#endif
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
index f042372d9f2e6..ea9b0f050f799 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
@@ -765,6 +765,7 @@ int amdgpu_vm_flush(struct amdgpu_ring *ring, struct amdgpu_job *job,
bool cleaner_shader_needed = false;
bool pasid_mapping_needed = false;
struct dma_fence *fence = NULL;
+ struct amdgpu_fence *af;
unsigned int patch;
int r;
@@ -830,6 +831,9 @@ int amdgpu_vm_flush(struct amdgpu_ring *ring, struct amdgpu_job *job,
r = amdgpu_fence_emit(ring, &fence, NULL, 0);
if (r)
return r;
+ /* this is part of the job's context */
+ af = container_of(fence, struct amdgpu_fence, base);
+ af->context = job->base.s_fence ? job->base.s_fence->finished.context : 0;
}
if (vm_flush_needed) {
--
2.50.0
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