[Intel-gfx] [PATCH v2] drm/i915: Cancel non-persistent contexts on close
Chris Wilson
chris at chris-wilson.co.uk
Wed Oct 2 14:23:15 UTC 2019
Normally, we rely on our hangcheck to prevent persistent batches from
hogging the GPU. However, if the user disables hangcheck, this mechanism
breaks down. Despite our insistence that this is unsafe, the users are
equally insistent that they want to use endless batches and will disable
the hangcheck mechanism. We are looking at perhaps replacing hangcheck
with a softer mechanism, that sends a pulse down the engine to check if
it is well. We can use the same preemptive pulse to flush an active
persistent context off the GPU upon context close, preventing resources
being lost and unkillable requests remaining on the GPU after process
termination. To avoid changing the ABI and accidentally breaking
existing userspace, we make the persistence of a context explicit and
enable it by default (matching current ABI). Userspace can opt out of
persistent mode (forcing requests to be cancelled when the context is
closed by process termination or explicitly) by a context parameter. To
facilitate existing use-cases of disabling hangcheck, if the modparam is
disabled (i915.enable_hangcheck=0), we disable persistence mode by
default. (Note, one of the outcomes for supporting endless mode will be
the removal of hangchecking, at which point opting into persistent mode
will be mandatory, or maybe the default perhaps controlled by cgroups.)
v2: Check for hangchecking at context termination, so that we are not
left with undying contexts from a craft user.
Testcase: igt/gem_ctx_persistence
Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
Cc: Michał Winiarski <michal.winiarski at intel.com>
Cc: Jon Bloomfield <jon.bloomfield at intel.com>
Reviewed-by: Jon Bloomfield <jon.bloomfield at intel.com>
---
drivers/gpu/drm/i915/Makefile | 1 +
drivers/gpu/drm/i915/gem/i915_gem_context.c | 132 ++++++++++++++++++
drivers/gpu/drm/i915/gem/i915_gem_context.h | 15 ++
.../gpu/drm/i915/gem/i915_gem_context_types.h | 1 +
.../gpu/drm/i915/gem/selftests/mock_context.c | 2 +
.../gpu/drm/i915/gt/intel_engine_heartbeat.c | 56 ++++++++
.../gpu/drm/i915/gt/intel_engine_heartbeat.h | 14 ++
drivers/gpu/drm/i915/gt/intel_engine_pm.c | 2 +-
drivers/gpu/drm/i915/i915_priolist_types.h | 1 +
include/uapi/drm/i915_drm.h | 15 ++
10 files changed, 238 insertions(+), 1 deletion(-)
create mode 100644 drivers/gpu/drm/i915/gt/intel_engine_heartbeat.c
create mode 100644 drivers/gpu/drm/i915/gt/intel_engine_heartbeat.h
diff --git a/drivers/gpu/drm/i915/Makefile b/drivers/gpu/drm/i915/Makefile
index 1f87c70a2842..561fa2bb3006 100644
--- a/drivers/gpu/drm/i915/Makefile
+++ b/drivers/gpu/drm/i915/Makefile
@@ -76,6 +76,7 @@ gt-y += \
gt/intel_breadcrumbs.o \
gt/intel_context.o \
gt/intel_engine_cs.o \
+ gt/intel_engine_heartbeat.o \
gt/intel_engine_pm.o \
gt/intel_engine_pool.o \
gt/intel_engine_sysfs.o \
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_context.c b/drivers/gpu/drm/i915/gem/i915_gem_context.c
index 0ab416887fc2..172fe95d863e 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_context.c
@@ -70,6 +70,7 @@
#include <drm/i915_drm.h>
#include "gt/intel_lrc_reg.h"
+#include "gt/intel_engine_heartbeat.h"
#include "gt/intel_engine_user.h"
#include "i915_gem_context.h"
@@ -375,6 +376,78 @@ void i915_gem_context_release(struct kref *ref)
queue_work(i915->wq, &i915->contexts.free_work);
}
+static inline struct i915_gem_engines *
+__context_engines_static(struct i915_gem_context *ctx)
+{
+ return rcu_dereference_protected(ctx->engines, true);
+}
+
+static void kill_context(struct i915_gem_context *ctx)
+{
+ intel_engine_mask_t tmp, active, reset;
+ struct intel_gt *gt = &ctx->i915->gt;
+ struct i915_gem_engines_iter it;
+ struct intel_engine_cs *engine;
+ struct intel_context *ce;
+
+ /*
+ * If we are already banned, it was due to a guilty request causing
+ * a reset and the entire context being evicted from the GPU.
+ */
+ if (i915_gem_context_is_banned(ctx))
+ return;
+
+ i915_gem_context_set_banned(ctx);
+
+ /*
+ * Map the user's engine back to the actual engines; one virtual
+ * engine will be mapped to multiple engines, and using ctx->engine[]
+ * the same engine may be have multiple instances in the user's map.
+ * However, we only care about pending requests, so only include
+ * engines on which there are incomplete requests.
+ */
+ active = 0;
+ for_each_gem_engine(ce, __context_engines_static(ctx), it) {
+ struct dma_fence *fence;
+
+ if (!ce->timeline)
+ continue;
+
+ fence = i915_active_fence_get(&ce->timeline->last_request);
+ if (!fence)
+ continue;
+
+ engine = to_request(fence)->engine;
+ if (HAS_EXECLISTS(gt->i915))
+ engine = intel_context_inflight(ce);
+ if (engine)
+ active |= engine->mask;
+
+ dma_fence_put(fence);
+ }
+
+ /*
+ * Send a "high priority pulse" down the engine to cause the
+ * current request to be momentarily preempted. (If it fails to
+ * be preempted, it will be reset). As we have marked our context
+ * as banned, any incomplete request, including any running, will
+ * be skipped following the preemption.
+ */
+ reset = 0;
+ for_each_engine_masked(engine, gt->i915, active, tmp)
+ if (intel_engine_pulse(engine))
+ reset |= engine->mask;
+
+ /*
+ * If we are unable to send a preemptive pulse to bump
+ * the context from the GPU, we have to resort to a full
+ * reset. We hope the collateral damage is worth it.
+ */
+ if (reset)
+ intel_gt_handle_error(gt, reset, 0,
+ "context closure in %s", ctx->name);
+}
+
static void context_close(struct i915_gem_context *ctx)
{
i915_gem_context_set_closed(ctx);
@@ -400,9 +473,47 @@ static void context_close(struct i915_gem_context *ctx)
lut_close(ctx);
mutex_unlock(&ctx->mutex);
+
+ /*
+ * If the user has disabled hangchecking, we can not be sure that
+ * the batches will ever complete after the context is closed,
+ * keep the context and all resources pinned forever. So in this
+ * case we opt to forcibly kill off all remaining requests on
+ * context close.
+ */
+ if (!i915_gem_context_is_persistent(ctx) ||
+ !i915_modparams.enable_hangcheck)
+ kill_context(ctx);
+
i915_gem_context_put(ctx);
}
+static int __context_set_persistence(struct i915_gem_context *ctx, bool state)
+{
+ if (i915_gem_context_is_persistent(ctx) == state)
+ return 0;
+
+ if (state) {
+ /*
+ * Only contexts that are short-lived [that will expire or be
+ * reset] are allowed to survive past termination. We require
+ * hangcheck to ensure that the persistent requests are healthy.
+ */
+ if (!i915_modparams.enable_hangcheck)
+ return -EINVAL;
+
+ i915_gem_context_set_persistence(ctx);
+ } else {
+ /* To cancel a context we use "preempt-to-idle" */
+ if (!(ctx->i915->caps.scheduler & I915_SCHEDULER_CAP_PREEMPTION))
+ return -ENODEV;
+
+ i915_gem_context_clear_persistence(ctx);
+ }
+
+ return 0;
+}
+
static struct i915_gem_context *
__create_context(struct drm_i915_private *i915)
{
@@ -439,6 +550,7 @@ __create_context(struct drm_i915_private *i915)
i915_gem_context_set_bannable(ctx);
i915_gem_context_set_recoverable(ctx);
+ __context_set_persistence(ctx, true /* cgroup hook? */);
for (i = 0; i < ARRAY_SIZE(ctx->hang_timestamp); i++)
ctx->hang_timestamp[i] = jiffies - CONTEXT_FAST_HANG_JIFFIES;
@@ -597,6 +709,7 @@ i915_gem_context_create_kernel(struct drm_i915_private *i915, int prio)
}
i915_gem_context_clear_bannable(ctx);
+ i915_gem_context_set_persistence(ctx);
ctx->sched.priority = I915_USER_PRIORITY(prio);
GEM_BUG_ON(!i915_gem_context_is_kernel(ctx));
@@ -1724,6 +1837,16 @@ get_engines(struct i915_gem_context *ctx,
return err;
}
+static int
+set_persistence(struct i915_gem_context *ctx,
+ const struct drm_i915_gem_context_param *args)
+{
+ if (args->size)
+ return -EINVAL;
+
+ return __context_set_persistence(ctx, args->value);
+}
+
static int ctx_setparam(struct drm_i915_file_private *fpriv,
struct i915_gem_context *ctx,
struct drm_i915_gem_context_param *args)
@@ -1801,6 +1924,10 @@ static int ctx_setparam(struct drm_i915_file_private *fpriv,
ret = set_engines(ctx, args);
break;
+ case I915_CONTEXT_PARAM_PERSISTENCE:
+ ret = set_persistence(ctx, args);
+ break;
+
case I915_CONTEXT_PARAM_BAN_PERIOD:
default:
ret = -EINVAL;
@@ -2250,6 +2377,11 @@ int i915_gem_context_getparam_ioctl(struct drm_device *dev, void *data,
ret = get_engines(ctx, args);
break;
+ case I915_CONTEXT_PARAM_PERSISTENCE:
+ args->size = 0;
+ args->value = i915_gem_context_is_persistent(ctx);
+ break;
+
case I915_CONTEXT_PARAM_BAN_PERIOD:
default:
ret = -EINVAL;
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_context.h b/drivers/gpu/drm/i915/gem/i915_gem_context.h
index 176978608b6f..e0f5b6c6a331 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_context.h
+++ b/drivers/gpu/drm/i915/gem/i915_gem_context.h
@@ -74,6 +74,21 @@ static inline void i915_gem_context_clear_recoverable(struct i915_gem_context *c
clear_bit(UCONTEXT_RECOVERABLE, &ctx->user_flags);
}
+static inline bool i915_gem_context_is_persistent(const struct i915_gem_context *ctx)
+{
+ return test_bit(UCONTEXT_PERSISTENCE, &ctx->user_flags);
+}
+
+static inline void i915_gem_context_set_persistence(struct i915_gem_context *ctx)
+{
+ set_bit(UCONTEXT_PERSISTENCE, &ctx->user_flags);
+}
+
+static inline void i915_gem_context_clear_persistence(struct i915_gem_context *ctx)
+{
+ clear_bit(UCONTEXT_PERSISTENCE, &ctx->user_flags);
+}
+
static inline bool i915_gem_context_is_banned(const struct i915_gem_context *ctx)
{
return test_bit(CONTEXT_BANNED, &ctx->flags);
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_context_types.h b/drivers/gpu/drm/i915/gem/i915_gem_context_types.h
index 260d59cc3de8..daf1ea5075a6 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_context_types.h
+++ b/drivers/gpu/drm/i915/gem/i915_gem_context_types.h
@@ -137,6 +137,7 @@ struct i915_gem_context {
#define UCONTEXT_NO_ERROR_CAPTURE 1
#define UCONTEXT_BANNABLE 2
#define UCONTEXT_RECOVERABLE 3
+#define UCONTEXT_PERSISTENCE 4
/**
* @flags: small set of booleans
diff --git a/drivers/gpu/drm/i915/gem/selftests/mock_context.c b/drivers/gpu/drm/i915/gem/selftests/mock_context.c
index be8974ccff24..0d1a275ec316 100644
--- a/drivers/gpu/drm/i915/gem/selftests/mock_context.c
+++ b/drivers/gpu/drm/i915/gem/selftests/mock_context.c
@@ -23,6 +23,8 @@ mock_context(struct drm_i915_private *i915,
INIT_LIST_HEAD(&ctx->link);
ctx->i915 = i915;
+ i915_gem_context_set_persistence(ctx);
+
mutex_init(&ctx->engines_mutex);
e = default_engines(ctx);
if (IS_ERR(e))
diff --git a/drivers/gpu/drm/i915/gt/intel_engine_heartbeat.c b/drivers/gpu/drm/i915/gt/intel_engine_heartbeat.c
new file mode 100644
index 000000000000..2fc413f9d506
--- /dev/null
+++ b/drivers/gpu/drm/i915/gt/intel_engine_heartbeat.c
@@ -0,0 +1,56 @@
+/*
+ * SPDX-License-Identifier: MIT
+ *
+ * Copyright © 2019 Intel Corporation
+ */
+
+#include "i915_request.h"
+
+#include "intel_context.h"
+#include "intel_engine_heartbeat.h"
+#include "intel_engine_pm.h"
+#include "intel_engine.h"
+#include "intel_gt.h"
+
+static void idle_pulse(struct intel_engine_cs *engine, struct i915_request *rq)
+{
+ engine->wakeref_serial = READ_ONCE(engine->serial) + 1;
+ i915_request_add_active_barriers(rq);
+}
+
+int intel_engine_pulse(struct intel_engine_cs *engine)
+{
+ struct i915_sched_attr attr = { .priority = I915_PRIORITY_BARRIER };
+ struct intel_context *ce = engine->kernel_context;
+ struct i915_request *rq;
+ int err = 0;
+
+ if (!intel_engine_has_preemption(engine))
+ return -ENODEV;
+
+ if (!intel_engine_pm_get_if_awake(engine))
+ return 0;
+
+ if (mutex_lock_interruptible(&ce->timeline->mutex))
+ goto out_rpm;
+
+ intel_context_enter(ce);
+ rq = __i915_request_create(ce, GFP_NOWAIT | __GFP_NOWARN);
+ intel_context_exit(ce);
+ if (IS_ERR(rq)) {
+ err = PTR_ERR(rq);
+ goto out_unlock;
+ }
+
+ rq->flags |= I915_REQUEST_SENTINEL;
+ idle_pulse(engine, rq);
+
+ __i915_request_commit(rq);
+ __i915_request_queue(rq, &attr);
+
+out_unlock:
+ mutex_unlock(&ce->timeline->mutex);
+out_rpm:
+ intel_engine_pm_put(engine);
+ return err;
+}
diff --git a/drivers/gpu/drm/i915/gt/intel_engine_heartbeat.h b/drivers/gpu/drm/i915/gt/intel_engine_heartbeat.h
new file mode 100644
index 000000000000..b950451b5998
--- /dev/null
+++ b/drivers/gpu/drm/i915/gt/intel_engine_heartbeat.h
@@ -0,0 +1,14 @@
+/*
+ * SPDX-License-Identifier: MIT
+ *
+ * Copyright © 2019 Intel Corporation
+ */
+
+#ifndef INTEL_ENGINE_HEARTBEAT_H
+#define INTEL_ENGINE_HEARTBEAT_H
+
+struct intel_engine_cs;
+
+int intel_engine_pulse(struct intel_engine_cs *engine);
+
+#endif /* INTEL_ENGINE_HEARTBEAT_H */
diff --git a/drivers/gpu/drm/i915/gt/intel_engine_pm.c b/drivers/gpu/drm/i915/gt/intel_engine_pm.c
index 8e5e513eddc9..86c0b2280b7b 100644
--- a/drivers/gpu/drm/i915/gt/intel_engine_pm.c
+++ b/drivers/gpu/drm/i915/gt/intel_engine_pm.c
@@ -111,7 +111,7 @@ static bool switch_to_kernel_context(struct intel_engine_cs *engine)
i915_request_add_active_barriers(rq);
/* Install ourselves as a preemption barrier */
- rq->sched.attr.priority = I915_PRIORITY_UNPREEMPTABLE;
+ rq->sched.attr.priority = I915_PRIORITY_BARRIER;
__i915_request_commit(rq);
/* Release our exclusive hold on the engine */
diff --git a/drivers/gpu/drm/i915/i915_priolist_types.h b/drivers/gpu/drm/i915/i915_priolist_types.h
index 21037a2e2038..ae8bb3cb627e 100644
--- a/drivers/gpu/drm/i915/i915_priolist_types.h
+++ b/drivers/gpu/drm/i915/i915_priolist_types.h
@@ -39,6 +39,7 @@ enum {
* active request.
*/
#define I915_PRIORITY_UNPREEMPTABLE INT_MAX
+#define I915_PRIORITY_BARRIER INT_MAX
#define __NO_PREEMPTION (I915_PRIORITY_WAIT)
diff --git a/include/uapi/drm/i915_drm.h b/include/uapi/drm/i915_drm.h
index 30c542144016..eb9e704d717a 100644
--- a/include/uapi/drm/i915_drm.h
+++ b/include/uapi/drm/i915_drm.h
@@ -1565,6 +1565,21 @@ struct drm_i915_gem_context_param {
* i915_context_engines_bond (I915_CONTEXT_ENGINES_EXT_BOND)
*/
#define I915_CONTEXT_PARAM_ENGINES 0xa
+
+/*
+ * I915_CONTEXT_PARAM_PERSISTENCE:
+ *
+ * Allow the context and active rendering to survive the process until
+ * completion. Persistence allows fire-and-forget clients to queue up a
+ * bunch of work, hand the output over to a display server and the quit.
+ * If the context is not marked as persistent, upon closing (either via
+ * an explicit DRM_I915_GEM_CONTEXT_DESTROY or implicitly from file closure
+ * or process termination), the context and any outstanding requests will be
+ * cancelled (and exported fences for cancelled requests marked as -EIO).
+ *
+ * By default, new contexts allow persistence.
+ */
+#define I915_CONTEXT_PARAM_PERSISTENCE 0xb
/* Must be kept compact -- no holes and well documented */
__u64 value;
--
2.23.0
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