On 19/03/2019 11:57, Chris Wilson wrote:
Having allowed the user to define a set of engines that they will want
to only use, we go one step further and allow them to bind those engines
into a single virtual instance. Submitting a batch to the virtual engine
will then forward it to any one of the set in a manner as best to
distribute load. The virtual engine has a single timeline across all
engines (it operates as a single queue), so it is not able to concurrently
run batches across multiple engines by itself; that is left up to the user
to submit multiple concurrent batches to multiple queues. Multiple users
will be load balanced across the system.
The mechanism used for load balancing in this patch is a late greedy
balancer. When a request is ready for execution, it is added to each
engine's queue, and when an engine is ready for its next request it
claims it from the virtual engine. The first engine to do so, wins, i.e.
the request is executed at the earliest opportunity (idle moment) in the
system.
As not all HW is created equal, the user is still able to skip the
virtual engine and execute the batch on a specific engine, all within the
same queue. It will then be executed in order on the correct engine,
with execution on other virtual engines being moved away due to the load
detection.
A couple of areas for potential improvement left!
- The virtual engine always take priority over equal-priority tasks.
Mostly broken up by applying FQ_CODEL rules for prioritising new clients,
and hopefully the virtual and real engines are not then congested (i.e.
all work is via virtual engines, or all work is to the real engine).
- We require the breadcrumb irq around every virtual engine request. For
normal engines, we eliminate the need for the slow round trip via
interrupt by using the submit fence and queueing in order. For virtual
engines, we have to allow any job to transfer to a new ring, and cannot
coalesce the submissions, so require the completion fence instead,
forcing the persistent use of interrupts.
- We only drip feed single requests through each virtual engine and onto
the physical engines, even if there was enough work to fill all ELSP,
leaving small stalls with an idle CS event at the end of every request.
Could we be greedy and fill both slots? Being lazy is virtuous for load
distribution on less-than-full workloads though.
Other areas of improvement are more general, such as reducing lock
contention, reducing dispatch overhead, looking at direct submission
rather than bouncing around tasklets etc.
sseu: Lift the restriction to allow sseu to be reconfigured on virtual
engines composed of RENDER_CLASS (rcs).
v2: macroize check_user_mbz()
v3: Cancel virtual engines on wedging
v4: Commence commenting
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
---
drivers/gpu/drm/i915/i915_gem.h | 5 +
drivers/gpu/drm/i915/i915_gem_context.c | 126 ++++-
drivers/gpu/drm/i915/i915_scheduler.c | 18 +-
drivers/gpu/drm/i915/i915_timeline_types.h | 1 +
drivers/gpu/drm/i915/intel_engine_types.h | 8 +
drivers/gpu/drm/i915/intel_lrc.c | 567 ++++++++++++++++++++-
drivers/gpu/drm/i915/intel_lrc.h | 11 +
drivers/gpu/drm/i915/selftests/intel_lrc.c | 165 ++++++
include/uapi/drm/i915_drm.h | 30 ++
9 files changed, 912 insertions(+), 19 deletions(-)
diff --git a/drivers/gpu/drm/i915/i915_gem.h b/drivers/gpu/drm/i915/i915_gem.h
index 5c073fe73664..3ca855505715 100644
--- a/drivers/gpu/drm/i915/i915_gem.h
+++ b/drivers/gpu/drm/i915/i915_gem.h
@@ -96,4 +96,9 @@ static inline bool __tasklet_enable(struct tasklet_struct *t)
return atomic_dec_and_test(&t->count);
}
+static inline bool __tasklet_is_scheduled(struct tasklet_struct *t)
+{
+ return test_bit(TASKLET_STATE_SCHED, &t->state);
+}
+
#endif /* __I915_GEM_H__ */
diff --git a/drivers/gpu/drm/i915/i915_gem_context.c b/drivers/gpu/drm/i915/i915_gem_context.c
index cbd76ef95115..8d8fcc8c7a86 100644
--- a/drivers/gpu/drm/i915/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/i915_gem_context.c
@@ -86,6 +86,7 @@
*/
#include <linux/log2.h>
+#include <linux/nospec.h>
#include <drm/i915_drm.h>
@@ -94,6 +95,7 @@
#include "i915_trace.h"
#include "i915_user_extensions.h"
#include "intel_lrc_reg.h"
+#include "intel_lrc.h"
#include "intel_workarounds.h"
#define ALL_L3_SLICES(dev) (1 << NUM_L3_SLICES(dev)) - 1
@@ -241,6 +243,20 @@ static void release_hw_id(struct i915_gem_context *ctx)
mutex_unlock(&i915->contexts.mutex);
}
+static void free_engines(struct intel_engine_cs **engines, int count)
+{
+ int i;
+
+ if (ZERO_OR_NULL_PTR(engines))
+ return;
+
+ /* We own the veng we created; regular engines are ignored */
+ for (i = 0; i < count; i++)
+ intel_virtual_engine_destroy(engines[i]);
+
+ kfree(engines);
+}
+
static void i915_gem_context_free(struct i915_gem_context *ctx)
{
struct intel_context *it, *n;
@@ -251,8 +267,7 @@ static void i915_gem_context_free(struct i915_gem_context *ctx)
release_hw_id(ctx);
i915_ppgtt_put(ctx->ppgtt);
-
- kfree(ctx->engines);
+ free_engines(ctx->engines, ctx->num_engines);
rbtree_postorder_for_each_entry_safe(it, n, &ctx->hw_contexts, node)
intel_context_put(it);
@@ -1239,7 +1254,6 @@ __i915_gem_context_reconfigure_sseu(struct i915_gem_context *ctx,
int ret = 0;
GEM_BUG_ON(INTEL_GEN(ctx->i915) < 8);
- GEM_BUG_ON(engine->id != RCS0);
ce = intel_context_pin_lock(ctx, engine);
if (IS_ERR(ce))
@@ -1433,7 +1447,80 @@ struct set_engines {
unsigned int num_engines;
};
+static int
+set_engines__load_balance(struct i915_user_extension __user *base, void *data)
+{
+ struct i915_context_engines_load_balance __user *ext =
+ container_of_user(base, typeof(*ext), base);
+ const struct set_engines *set = data;
+ struct intel_engine_cs *ve;
+ unsigned int n;
+ u64 mask;
+ u16 idx;
+ int err;
+
+ if (!HAS_EXECLISTS(set->ctx->i915))
+ return -ENODEV;
+
+ if (USES_GUC_SUBMISSION(set->ctx->i915))
+ return -ENODEV; /* not implement yet */
+
+ if (get_user(idx, &ext->engine_index))
+ return -EFAULT;
+
+ if (idx >= set->num_engines)
+ return -EINVAL;
+
+ idx = array_index_nospec(idx, set->num_engines);
+ if (set->engines[idx])
+ return -EEXIST;
+
+ err = check_user_mbz(&ext->mbz16);
+ if (err)
+ return err;
+
+ err = check_user_mbz(&ext->flags);
+ if (err)
+ return err;
+
+ for (n = 0; n < ARRAY_SIZE(ext->mbz64); n++) {
+ err = check_user_mbz(&ext->mbz64[n]);
+ if (err)
+ return err;
+ }
+
+ if (get_user(mask, &ext->engines_mask))
+ return -EFAULT;
+
+ mask &= GENMASK_ULL(set->num_engines - 1, 0) & ~BIT_ULL(idx);
+ if (!mask)
+ return -EINVAL;
+
+ if (is_power_of_2(mask)) {
+ ve = set->engines[__ffs64(mask)];
+ } else {
+ struct intel_engine_cs *stack[64];
+ int bit;
+
+ n = 0;
+ for_each_set_bit(bit, (unsigned long *)&mask, set->num_engines)
+ stack[n++] = set->engines[bit];
+
+ ve = intel_execlists_create_virtual(set->ctx, stack, n);
+ }
+ if (IS_ERR(ve))
+ return PTR_ERR(ve);
+
+ if (cmpxchg(&set->engines[idx], NULL, ve)) {
+ intel_virtual_engine_destroy(ve);
+ return -EEXIST;
+ }
+
+ return 0;
+}
+
static const i915_user_extension_fn set_engines__extensions[] = {
+ [I915_CONTEXT_ENGINES_EXT_LOAD_BALANCE] = set_engines__load_balance,
};
static int
@@ -1497,13 +1584,13 @@ set_engines(struct i915_gem_context *ctx,
ARRAY_SIZE(set_engines__extensions),
&set);
if (err) {
- kfree(set.engines);
+ free_engines(set.engines, set.num_engines);
return err;
}
out:
mutex_lock(&ctx->i915->drm.struct_mutex);
- kfree(ctx->engines);
+ free_engines(ctx->engines, ctx->num_engines);
ctx->engines = set.engines;
ctx->num_engines = set.num_engines;
mutex_unlock(&ctx->i915->drm.struct_mutex);
@@ -1692,7 +1779,7 @@ static int clone_engines(struct i915_gem_context *dst,
struct i915_gem_context *src)
{
struct intel_engine_cs **engines;
- unsigned int num_engines;
+ unsigned int num_engines, i;
mutex_lock(&src->i915->drm.struct_mutex); /* serialise src->engine[] */
@@ -1707,11 +1794,36 @@ static int clone_engines(struct i915_gem_context *dst,
mutex_unlock(&src->i915->drm.struct_mutex);
return -ENOMEM;
}
+
+ /*
+ * Virtual engines are singletons; they can only exist
+ * inside a single context, because they embed their
+ * HW context... As each virtual context implies a single
+ * timeline (each engine can only dequeue a single request
+ * at any time), it would be surprising for two contexts
+ * to use the same engine. So let's create a copy of
+ * the virtual engine instead.
+ */
+ for (i = 0; i < num_engines; i++) {
+ struct intel_engine_cs *engine = engines[i];
+
+ if (!engine || !intel_engine_is_virtual(engine))
+ continue;
+
+ engine = intel_execlists_clone_virtual(dst, engine);
+ if (IS_ERR(engine)) {
+ free_engines(engines, i);
+ mutex_unlock(&src->i915->drm.struct_mutex);
+ return PTR_ERR(engine);
+ }
+
+ engines[i] = engine;
+ }
}
mutex_unlock(&src->i915->drm.struct_mutex);
- kfree(dst->engines);
+ free_engines(dst->engines, dst->num_engines);
dst->engines = engines;
dst->num_engines = num_engines;
return 0;
diff --git a/drivers/gpu/drm/i915/i915_scheduler.c b/drivers/gpu/drm/i915/i915_scheduler.c
index e0f609d01564..8cff4f6d6158 100644
--- a/drivers/gpu/drm/i915/i915_scheduler.c
+++ b/drivers/gpu/drm/i915/i915_scheduler.c
@@ -247,17 +247,26 @@ sched_lock_engine(const struct i915_sched_node *node,
struct intel_engine_cs *locked,
struct sched_cache *cache)
{
- struct intel_engine_cs *engine = node_to_request(node)->engine;
+ const struct i915_request *rq = node_to_request(node);
+ struct intel_engine_cs *engine;
GEM_BUG_ON(!locked);
- if (engine != locked) {
+ /*
+ * Virtual engines complicate acquiring the engine timeline lock,
+ * as their rq->engine pointer is not stable until under that
+ * engine lock. The simple ploy we use is to take the lock then
+ * check that the rq still belongs to the newly locked engine.
+ */
+ while (locked != (engine = READ_ONCE(rq->engine))) {
spin_unlock(&locked->timeline.lock);
memset(cache, 0, sizeof(*cache));
spin_lock(&engine->timeline.lock);
+ locked = engine;
}
- return engine;
+ GEM_BUG_ON(locked != engine);
+ return locked;
}
static bool inflight(const struct i915_request *rq,
@@ -370,8 +379,11 @@ static void __i915_schedule(struct i915_request *rq,
if (prio <= node->attr.priority || node_signaled(node))
continue;
+ GEM_BUG_ON(node_to_request(node)->engine != engine);
+
node->attr.priority = prio;
if (!list_empty(&node->link)) {
+ GEM_BUG_ON(intel_engine_is_virtual(engine));
if (!cache.priolist)
cache.priolist =
i915_sched_lookup_priolist(engine,
diff --git a/drivers/gpu/drm/i915/i915_timeline_types.h b/drivers/gpu/drm/i915/i915_timeline_types.h
index 1f5b55d9ffb5..57c79830bb8c 100644
--- a/drivers/gpu/drm/i915/i915_timeline_types.h
+++ b/drivers/gpu/drm/i915/i915_timeline_types.h
@@ -26,6 +26,7 @@ struct i915_timeline {
spinlock_t lock;
#define TIMELINE_CLIENT 0 /* default subclass */
#define TIMELINE_ENGINE 1
+#define TIMELINE_VIRTUAL 2
struct mutex mutex; /* protects the flow of requests */
unsigned int pin_count;
diff --git a/drivers/gpu/drm/i915/intel_engine_types.h b/drivers/gpu/drm/i915/intel_engine_types.h
index cef1e71a7401..4d526767c371 100644
--- a/drivers/gpu/drm/i915/intel_engine_types.h
+++ b/drivers/gpu/drm/i915/intel_engine_types.h
@@ -224,6 +224,7 @@ struct intel_engine_execlists {
* @queue: queue of requests, in priority lists
*/
struct rb_root_cached queue;
+ struct rb_root_cached virtual;
/**
* @csb_write: control register for Context Switch buffer
@@ -429,6 +430,7 @@ struct intel_engine_cs {
#define I915_ENGINE_SUPPORTS_STATS BIT(1)
#define I915_ENGINE_HAS_PREEMPTION BIT(2)
#define I915_ENGINE_HAS_SEMAPHORES BIT(3)
+#define I915_ENGINE_IS_VIRTUAL BIT(4)
unsigned int flags;
/*
@@ -512,6 +514,12 @@ intel_engine_has_semaphores(const struct intel_engine_cs *engine)
return engine->flags & I915_ENGINE_HAS_SEMAPHORES;
}
+static inline bool
+intel_engine_is_virtual(const struct intel_engine_cs *engine)
+{
+ return engine->flags & I915_ENGINE_IS_VIRTUAL;
+}
+
#define instdone_slice_mask(dev_priv__) \
(IS_GEN(dev_priv__, 7) ? \
1 : RUNTIME_INFO(dev_priv__)->sseu.slice_mask)
diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
index 0e64317ddcbf..a7f0235f19c5 100644
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -166,6 +166,41 @@
#define ACTIVE_PRIORITY (I915_PRIORITY_NEWCLIENT | I915_PRIORITY_NOSEMAPHORE)
+struct virtual_engine {
+ struct intel_engine_cs base;
+ struct intel_context context;
+
+ /*
+ * We allow only a single request through the virtual engine at a time
+ * (each request in the timeline waits for the completion fence of
+ * the previous before being submitted). By restricting ourselves to
+ * only submitting a single request, each request is placed on to a
+ * physical to maximise load spreading (by virtue of the late greedy
+ * scheduling -- each real engine takes the next available request
+ * upon idling).
+ */
+ struct i915_request *request;
+
+ /*
+ * We keep a rbtree of available virtual engines inside each physical
+ * engine, sorted by priority. Here we preallocate the nodes we need
+ * for the virtual engine, indexed by physical_engine->id.
+ */
+ struct ve_node {
+ struct rb_node rb;
+ int prio;
+ } nodes[I915_NUM_ENGINES];
+
+ /* And finally, which physical engines this virtual engine maps onto. */
+ unsigned int count;
+ struct intel_engine_cs *siblings[0];
+};
+
+static struct virtual_engine *to_virtual_engine(struct intel_engine_cs *engine)
+{
+ return container_of(engine, struct virtual_engine, base);
+}
+
static int execlists_context_deferred_alloc(struct intel_context *ce,
struct intel_engine_cs *engine);
static void execlists_init_reg_state(u32 *reg_state,
@@ -229,7 +264,8 @@ static int queue_prio(const struct intel_engine_execlists *execlists)
}
static inline bool need_preempt(const struct intel_engine_cs *engine,
- const struct i915_request *rq)
+ const struct i915_request *rq,
+ struct rb_node *rb)
{
int last_prio;
@@ -264,6 +300,22 @@ static inline bool need_preempt(const struct intel_engine_cs *engine,
rq_prio(list_next_entry(rq, link)) > last_prio)
return true;
+ if (rb) { /* XXX virtual precedence */
+ struct virtual_engine *ve =
+ rb_entry(rb, typeof(*ve), nodes[engine->id].rb);
+ bool preempt = false;
+
+ if (engine == ve->siblings[0]) { /* only preempt one sibling */
+ spin_lock(&ve->base.timeline.lock);
+ if (ve->request)
+ preempt = rq_prio(ve->request) > last_prio;
+ spin_unlock(&ve->base.timeline.lock);
+ }
+
+ if (preempt)
+ return preempt;
+ }
+
/*
* If the inflight context did not trigger the preemption, then maybe
* it was the set of queued requests? Pick the highest priority in
@@ -382,6 +434,8 @@ __unwind_incomplete_requests(struct intel_engine_cs *engine)
list_for_each_entry_safe_reverse(rq, rn,
&engine->timeline.requests,
link) {
+ struct intel_engine_cs *owner;
+
if (i915_request_completed(rq))
break;
@@ -390,14 +444,30 @@ __unwind_incomplete_requests(struct intel_engine_cs *engine)
GEM_BUG_ON(rq->hw_context->active);
- GEM_BUG_ON(rq_prio(rq) == I915_PRIORITY_INVALID);
- if (rq_prio(rq) != prio) {
- prio = rq_prio(rq);
- pl = i915_sched_lookup_priolist(engine, prio);
- }
- GEM_BUG_ON(RB_EMPTY_ROOT(&engine->execlists.queue.rb_root));
+ /*
+ * Push the request back into the queue for later resubmission.
+ * If this request is not native to this physical engine (i.e.
+ * it came from a virtual source), push it back onto the virtual
+ * engine so that it can be moved across onto another physical
+ * engine as load dictates.
+ */
+ owner = rq->hw_context->engine;
+ if (likely(owner == engine)) {
+ GEM_BUG_ON(rq_prio(rq) == I915_PRIORITY_INVALID);
+ if (rq_prio(rq) != prio) {
+ prio = rq_prio(rq);
+ pl = i915_sched_lookup_priolist(engine, prio);
+ }
+ GEM_BUG_ON(RB_EMPTY_ROOT(&engine->execlists.queue.rb_root));
- list_add(&rq->sched.link, pl);
+ list_add(&rq->sched.link, pl);
+ } else {
+ if (__i915_request_has_started(rq))
+ rq->sched.attr.priority |= ACTIVE_PRIORITY;
+
+ rq->engine = owner;
+ owner->submit_request(rq);
+ }
active = rq;
}
@@ -659,6 +729,50 @@ static void complete_preempt_context(struct intel_engine_execlists *execlists)
execlists));
}
+static void virtual_update_register_offsets(u32 *regs,
+ struct intel_engine_cs *engine)
+{
+ u32 base = engine->mmio_base;
+
+ regs[CTX_CONTEXT_CONTROL] =
+ i915_mmio_reg_offset(RING_CONTEXT_CONTROL(engine));
+ regs[CTX_RING_HEAD] = i915_mmio_reg_offset(RING_HEAD(base));
+ regs[CTX_RING_TAIL] = i915_mmio_reg_offset(RING_TAIL(base));
+ regs[CTX_RING_BUFFER_START] = i915_mmio_reg_offset(RING_START(base));
+ regs[CTX_RING_BUFFER_CONTROL] = i915_mmio_reg_offset(RING_CTL(base));
+
+ regs[CTX_BB_HEAD_U] = i915_mmio_reg_offset(RING_BBADDR_UDW(base));
+ regs[CTX_BB_HEAD_L] = i915_mmio_reg_offset(RING_BBADDR(base));
+ regs[CTX_BB_STATE] = i915_mmio_reg_offset(RING_BBSTATE(base));
+ regs[CTX_SECOND_BB_HEAD_U] =
+ i915_mmio_reg_offset(RING_SBBADDR_UDW(base));
+ regs[CTX_SECOND_BB_HEAD_L] = i915_mmio_reg_offset(RING_SBBADDR(base));
+ regs[CTX_SECOND_BB_STATE] = i915_mmio_reg_offset(RING_SBBSTATE(base));
+
+ regs[CTX_CTX_TIMESTAMP] =
+ i915_mmio_reg_offset(RING_CTX_TIMESTAMP(base));
+ regs[CTX_PDP3_UDW] = i915_mmio_reg_offset(GEN8_RING_PDP_UDW(engine, 3));
+ regs[CTX_PDP3_LDW] = i915_mmio_reg_offset(GEN8_RING_PDP_LDW(engine, 3));
+ regs[CTX_PDP2_UDW] = i915_mmio_reg_offset(GEN8_RING_PDP_UDW(engine, 2));
+ regs[CTX_PDP2_LDW] = i915_mmio_reg_offset(GEN8_RING_PDP_LDW(engine, 2));
+ regs[CTX_PDP1_UDW] = i915_mmio_reg_offset(GEN8_RING_PDP_UDW(engine, 1));
+ regs[CTX_PDP1_LDW] = i915_mmio_reg_offset(GEN8_RING_PDP_LDW(engine, 1));
+ regs[CTX_PDP0_UDW] = i915_mmio_reg_offset(GEN8_RING_PDP_UDW(engine, 0));
+ regs[CTX_PDP0_LDW] = i915_mmio_reg_offset(GEN8_RING_PDP_LDW(engine, 0));
+
+ if (engine->class == RENDER_CLASS) {
+ regs[CTX_RCS_INDIRECT_CTX] =
+ i915_mmio_reg_offset(RING_INDIRECT_CTX(base));
+ regs[CTX_RCS_INDIRECT_CTX_OFFSET] =
+ i915_mmio_reg_offset(RING_INDIRECT_CTX_OFFSET(base));
+ regs[CTX_BB_PER_CTX_PTR] =
+ i915_mmio_reg_offset(RING_BB_PER_CTX_PTR(base));
+
+ regs[CTX_R_PWR_CLK_STATE] =
+ i915_mmio_reg_offset(GEN8_R_PWR_CLK_STATE);
+ }
+}
+
static void execlists_dequeue(struct intel_engine_cs *engine)
{
struct intel_engine_execlists * const execlists = &engine->execlists;
@@ -691,6 +805,37 @@ static void execlists_dequeue(struct intel_engine_cs *engine)
* and context switches) submission.
*/
+ for (rb = rb_first_cached(&execlists->virtual); rb; ) {
+ struct virtual_engine *ve =
+ rb_entry(rb, typeof(*ve), nodes[engine->id].rb);
+ struct i915_request *rq = READ_ONCE(ve->request);
+ struct intel_engine_cs *active;
+
+ if (!rq) { /* lazily cleanup after another engine handled rq */
+ rb_erase_cached(rb, &execlists->virtual);
+ RB_CLEAR_NODE(rb);
+ rb = rb_first_cached(&execlists->virtual);
+ continue;
+ }
+
+ /*
+ * We track when the HW has completed saving the context image
+ * (i.e. when we have seen the final CS event switching out of
+ * the context) and must not overwrite the context image before
+ * then. This restricts us to only using the active engine
+ * while the previous virtualized request is inflight (so
+ * we reuse the register offsets). This is a very small
+ * hystersis on the greedy seelction algorithm.
+ */
+ active = READ_ONCE(ve->context.active);
+ if (active && active != engine) {
+ rb = rb_next(rb);
+ continue;
+ }
+
+ break;
+ }
+
if (last) {
/*
* Don't resubmit or switch until all outstanding
@@ -712,7 +857,7 @@ static void execlists_dequeue(struct intel_engine_cs *engine)
if (!execlists_is_active(execlists, EXECLISTS_ACTIVE_HWACK))
return;
- if (need_preempt(engine, last)) {
+ if (need_preempt(engine, last, rb)) {
inject_preempt_context(engine);
return;
}
@@ -752,6 +897,72 @@ static void execlists_dequeue(struct intel_engine_cs *engine)
last->tail = last->wa_tail;
}
+ while (rb) { /* XXX virtual is always taking precedence */
+ struct virtual_engine *ve =
+ rb_entry(rb, typeof(*ve), nodes[engine->id].rb);
+ struct i915_request *rq;
+
+ spin_lock(&ve->base.timeline.lock);
+
+ rq = ve->request;
+ if (unlikely(!rq)) { /* lost the race to a sibling */
+ spin_unlock(&ve->base.timeline.lock);
+ rb_erase_cached(rb, &execlists->virtual);
+ RB_CLEAR_NODE(rb);
+ rb = rb_first_cached(&execlists->virtual);
+ continue;
+ }
+
+ if (rq_prio(rq) >= queue_prio(execlists)) {
+ if (last && !can_merge_rq(last, rq)) {
+ spin_unlock(&ve->base.timeline.lock);
+ return; /* leave this rq for another engine */
Should this engine attempt to dequeue something else? Maybe something
from the non-virtual queue for instance could be submitted/appended.
+ }
+
+ GEM_BUG_ON(rq->engine != &ve->base);
+ ve->request = NULL;
+ ve->base.execlists.queue_priority_hint = INT_MIN;
+ rb_erase_cached(rb, &execlists->virtual);
+ RB_CLEAR_NODE(rb);
+
+ GEM_BUG_ON(rq->hw_context != &ve->context);
+ rq->engine = engine;
+
+ if (engine != ve->siblings[0]) {
+ u32 *regs = ve->context.lrc_reg_state;
+ unsigned int n;
+
+ GEM_BUG_ON(READ_ONCE(ve->context.active));
+ virtual_update_register_offsets(regs, engine);
+
+ /*
+ * Move the bound engine to the top of the list
+ * for future execution. We then kick this
+ * tasklet first before checking others, so that
+ * we preferentially reuse this set of bound
+ * registers.
+ */
+ for (n = 1; n < ve->count; n++) {
+ if (ve->siblings[n] == engine) {
+ swap(ve->siblings[n],
+ ve->siblings[0]);
+ break;
+ }
+ }
+
+ GEM_BUG_ON(ve->siblings[0] != engine);
+ }
+
+ __i915_request_submit(rq);
+ trace_i915_request_in(rq, port_index(port, execlists));
+ submit = true;
+ last = rq;
+ }
+
+ spin_unlock(&ve->base.timeline.lock);
+ break;
+ }
+
while ((rb = rb_first_cached(&execlists->queue))) {
struct i915_priolist *p = to_priolist(rb);
struct i915_request *rq, *rn;
@@ -971,6 +1182,24 @@ static void execlists_cancel_requests(struct intel_engine_cs *engine)
i915_priolist_free(p);
}
+ /* Cancel all attached virtual engines */
+ while ((rb = rb_first_cached(&execlists->virtual))) {
+ struct virtual_engine *ve =
+ rb_entry(rb, typeof(*ve), nodes[engine->id].rb);
+
+ rb_erase_cached(rb, &execlists->virtual);
+ RB_CLEAR_NODE(rb);
+
+ spin_lock(&ve->base.timeline.lock);
+ if (ve->request) {
+ __i915_request_submit(ve->request);
+ dma_fence_set_error(&ve->request->fence, -EIO);
+ i915_request_mark_complete(ve->request);
+ ve->request = NULL;
+ }
+ spin_unlock(&ve->base.timeline.lock);
+ }
+
/* Remaining _unready_ requests will be nop'ed when submitted */
execlists->queue_priority_hint = INT_MIN;
@@ -2897,6 +3126,303 @@ void intel_lr_context_resume(struct drm_i915_private *i915)
}
}
+static void virtual_context_destroy(struct kref *kref)
+{
+ struct virtual_engine *ve =
+ container_of(kref, typeof(*ve), context.ref);
+ unsigned int n;
+
+ GEM_BUG_ON(ve->request);
+ GEM_BUG_ON(ve->context.active);
+
+ for (n = 0; n < ve->count; n++) {
+ struct intel_engine_cs *sibling = ve->siblings[n];
+ struct rb_node *node = &ve->nodes[sibling->id].rb;
+
+ if (RB_EMPTY_NODE(node))
+ continue;
+
+ spin_lock_irq(&sibling->timeline.lock);
+
+ if (!RB_EMPTY_NODE(node))
+ rb_erase_cached(node, &sibling->execlists.virtual);
+
+ spin_unlock_irq(&sibling->timeline.lock);
+ }
+ GEM_BUG_ON(__tasklet_is_scheduled(&ve->base.execlists.tasklet));
+
+ if (ve->context.state)
+ __execlists_context_fini(&ve->context);
+
+ i915_timeline_fini(&ve->base.timeline);
+ kfree(ve);
+}
+
+static void virtual_engine_initial_hint(struct virtual_engine *ve)
+{
+ int swp;
+
+ /*
+ * Pick a random sibling on starting to help spread the load around.
+ *
+ * New contexts are typically created with exactly the same order
+ * of siblings, and often started in batches. Due to the way we iterate
+ * the array of sibling when submitting requests, sibling[0] is
+ * prioritised for dequeuing. If we make sure that sibling[0] is fairly
+ * randomised across the system, we also help spread the load by the
+ * first engine we inspect being different each time.
+ *
+ * NB This does not force us to execute on this engine, it will just
+ * typically be the first we inspect for submission.
+ */
+ swp = prandom_u32_max(ve->count);
+ if (!swp)
+ return;
+
+ swap(ve->siblings[swp], ve->siblings[0]);
+ virtual_update_register_offsets(ve->context.lrc_reg_state,
+ ve->siblings[0]);
+}
+
+static int virtual_context_pin(struct intel_context *ce)
+{
+ struct virtual_engine *ve = container_of(ce, typeof(*ve), context);
+ int err;
+
+ /* Note: we must use a real engine class for setting up reg state */
+ err = __execlists_context_pin(ce, ve->siblings[0]);
+ if (err)
+ return err;
+
+ virtual_engine_initial_hint(ve);
+ return 0;
+}
+
+static const struct intel_context_ops virtual_context_ops = {
+ .pin = virtual_context_pin,
+ .unpin = execlists_context_unpin,
+
+ .destroy = virtual_context_destroy,
+};
+
+static void virtual_submission_tasklet(unsigned long data)
+{
+ struct virtual_engine * const ve = (struct virtual_engine *)data;
+ unsigned int n;
+ int prio;
+
+ prio = READ_ONCE(ve->base.execlists.queue_priority_hint);
+ if (prio == INT_MIN)
+ return;
When does it hit this return?
+
+ local_irq_disable();
+ for (n = 0; READ_ONCE(ve->request) && n < ve->count; n++) {
+ struct intel_engine_cs *sibling = ve->siblings[n];
+ struct ve_node * const node = &ve->nodes[sibling->id];
+ struct rb_node **parent, *rb;
+ bool first;
+
+ spin_lock(&sibling->timeline.lock);
+
+ if (!RB_EMPTY_NODE(&node->rb)) {
+ /*
+ * Cheat and avoid rebalancing the tree if we can
+ * reuse this node in situ.
+ */
+ first = rb_first_cached(&sibling->execlists.virtual) ==
+ &node->rb;
+ if (prio == node->prio || (prio > node->prio && first))
+ goto submit_engine;
+
+ rb_erase_cached(&node->rb, &sibling->execlists.virtual);
How the cheat works exactly? Avoids inserting into the tree in some
cases? And how does the real tasklet find this node then?
+ }
+
+ rb = NULL;
+ first = true;
+ parent = &sibling->execlists.virtual.rb_root.rb_node;
+ while (*parent) {
+ struct ve_node *other;
+
+ rb = *parent;
+ other = rb_entry(rb, typeof(*other), rb);
+ if (prio > other->prio) {
+ parent = &rb->rb_left;
+ } else {
+ parent = &rb->rb_right;
+ first = false;
+ }
+ }
+
+ rb_link_node(&node->rb, rb, parent);
+ rb_insert_color_cached(&node->rb,
+ &sibling->execlists.virtual,
+ first);
+
+submit_engine:
+ GEM_BUG_ON(RB_EMPTY_NODE(&node->rb));
+ node->prio = prio;
+ if (first && prio > sibling->execlists.queue_priority_hint) {
+ sibling->execlists.queue_priority_hint = prio;
+ tasklet_hi_schedule(&sibling->execlists.tasklet);
+ }
+
+ spin_unlock(&sibling->timeline.lock);
+ }
+ local_irq_enable();
+}
+
+static void virtual_submit_request(struct i915_request *request)
+{
+ struct virtual_engine *ve = to_virtual_engine(request->engine);
+
+ GEM_BUG_ON(ve->base.submit_request != virtual_submit_request);
+
+ GEM_BUG_ON(ve->request);
+ ve->base.execlists.queue_priority_hint = rq_prio(request);
+ WRITE_ONCE(ve->request, request);
+
+ tasklet_schedule(&ve->base.execlists.tasklet);
+}
+
+struct intel_engine_cs *
+intel_execlists_create_virtual(struct i915_gem_context *ctx,
+ struct intel_engine_cs **siblings,
+ unsigned int count)
+{
+ struct virtual_engine *ve;
+ unsigned int n;
+ int err;
+
+ if (!count)
+ return ERR_PTR(-EINVAL);
+
+ ve = kzalloc(struct_size(ve, siblings, count), GFP_KERNEL);
+ if (!ve)
+ return ERR_PTR(-ENOMEM);
+
+ ve->base.i915 = ctx->i915;
+ ve->base.id = -1;
+ ve->base.class = OTHER_CLASS;
+ ve->base.uabi_class = I915_ENGINE_CLASS_INVALID;
+ ve->base.instance = I915_ENGINE_CLASS_INVALID_VIRTUAL;
+ ve->base.flags = I915_ENGINE_IS_VIRTUAL;
+
+ snprintf(ve->base.name, sizeof(ve->base.name), "virtual");
+
+ err = i915_timeline_init(ctx->i915, &ve->base.timeline, NULL);
+ if (err)
+ goto err_put;
+ i915_timeline_set_subclass(&ve->base.timeline, TIMELINE_VIRTUAL);
+
+ ve->base.cops = &virtual_context_ops;
+ ve->base.request_alloc = execlists_request_alloc;
+
+ ve->base.schedule = i915_schedule;
+ ve->base.submit_request = virtual_submit_request;
+
+ ve->base.execlists.queue_priority_hint = INT_MIN;
+ tasklet_init(&ve->base.execlists.tasklet,
+ virtual_submission_tasklet,
+ (unsigned long)ve);
+
+ intel_context_init(&ve->context, ctx, &ve->base);
+
+ for (n = 0; n < count; n++) {
+ struct intel_engine_cs *sibling = siblings[n];
+
+ GEM_BUG_ON(!is_power_of_2(sibling->mask));
+ if (sibling->mask & ve->base.mask)
+ continue;
Continuing from the previous round - should we -EINVAL if two of the
same are found in the map? Since we are going to silently drop it..
perhaps better to disallow.
+
+ /*
+ * The virtual engine implementation is tightly coupled to
+ * the execlists backend -- we push out request directly
+ * into a tree inside each physical engine. We could support
+ * layering if we handling cloning of the requests and
+ * submitting a copy into each backend.
+ */
+ if (sibling->execlists.tasklet.func !=
+ execlists_submission_tasklet) {
+ err = -ENODEV;
+ goto err_put;
+ }
+
+ GEM_BUG_ON(RB_EMPTY_NODE(&ve->nodes[sibling->id].rb));
+ RB_CLEAR_NODE(&ve->nodes[sibling->id].rb);
+
+ ve->siblings[ve->count++] = sibling;
+ ve->base.mask |= sibling->mask;
+
+ /*
+ * All physical engines must be compatible for their emission
+ * functions (as we build the instructions during request
+ * construction and do not alter them before submission
+ * on the physical engine). We use the engine class as a guide
+ * here, although that could be refined.
+ */
+ if (ve->base.class != OTHER_CLASS) {
+ if (ve->base.class != sibling->class) {
+ err = -EINVAL;
+ goto err_put;
+ }
+ continue;
+ }
+
+ ve->base.class = sibling->class;
+ snprintf(ve->base.name, sizeof(ve->base.name),
+ "v%dx%d", ve->base.class, count);
+ ve->base.context_size = sibling->context_size;
+
+ ve->base.emit_bb_start = sibling->emit_bb_start;
+ ve->base.emit_flush = sibling->emit_flush;
+ ve->base.emit_init_breadcrumb = sibling->emit_init_breadcrumb;
+ ve->base.emit_fini_breadcrumb = sibling->emit_fini_breadcrumb;
+ ve->base.emit_fini_breadcrumb_dw =
+ sibling->emit_fini_breadcrumb_dw;
+ }
+
+ /* gracefully replace a degenerate virtual engine */
+ if (ve->count == 1) {
+ struct intel_engine_cs *actual = ve->siblings[0];
+ intel_context_put(&ve->context);
+ return actual;
+ }
+
+ __intel_context_insert(ctx, &ve->base, &ve->context);
+ return &ve->base;
+
+err_put:
+ intel_context_put(&ve->context);
+ return ERR_PTR(err);
+}
+
+struct intel_engine_cs *
+intel_execlists_clone_virtual(struct i915_gem_context *ctx,
+ struct intel_engine_cs *src)
+{
+ struct virtual_engine *se = to_virtual_engine(src);
+ struct intel_engine_cs *dst;
+
+ dst = intel_execlists_create_virtual(ctx,
+ se->siblings,
+ se->count);
+ if (IS_ERR(dst))
+ return dst;
+
+ return dst;
+}
+
+void intel_virtual_engine_destroy(struct intel_engine_cs *engine)
+{
+ struct virtual_engine *ve = to_virtual_engine(engine);
+
+ if (!engine || !intel_engine_is_virtual(engine))
+ return;
+
+ __intel_context_remove(&ve->context);
+ intel_context_put(&ve->context);
+}
+
void intel_execlists_show_requests(struct intel_engine_cs *engine,
struct drm_printer *m,
void (*show_request)(struct drm_printer *m,
@@ -2954,6 +3480,29 @@ void intel_execlists_show_requests(struct intel_engine_cs *engine,
show_request(m, last, "\t\tQ ");
}
+ last = NULL;
+ count = 0;
+ for (rb = rb_first_cached(&execlists->virtual); rb; rb = rb_next(rb)) {
+ struct virtual_engine *ve =
+ rb_entry(rb, typeof(*ve), nodes[engine->id].rb);
+ struct i915_request *rq = READ_ONCE(ve->request);
+
+ if (rq) {
+ if (count++ < max - 1)
+ show_request(m, rq, "\t\tV ");
+ else
+ last = rq;
+ }
+ }
+ if (last) {
+ if (count > max) {
+ drm_printf(m,
+ "\t\t...skipping %d virtual requests...\n",
+ count - max);
+ }
+ show_request(m, last, "\t\tV ");
+ }
+
spin_unlock_irqrestore(&engine->timeline.lock, flags);
}
diff --git a/drivers/gpu/drm/i915/intel_lrc.h b/drivers/gpu/drm/i915/intel_lrc.h
index f1aec8a6986f..9d90dc68e02b 100644
--- a/drivers/gpu/drm/i915/intel_lrc.h
+++ b/drivers/gpu/drm/i915/intel_lrc.h
@@ -112,6 +112,17 @@ void intel_execlists_show_requests(struct intel_engine_cs *engine,
const char *prefix),
unsigned int max);
+struct intel_engine_cs *
+intel_execlists_create_virtual(struct i915_gem_context *ctx,
+ struct intel_engine_cs **siblings,
+ unsigned int count);
+
+struct intel_engine_cs *
+intel_execlists_clone_virtual(struct i915_gem_context *ctx,
+ struct intel_engine_cs *src);
+
+void intel_virtual_engine_destroy(struct intel_engine_cs *engine);
+
u32 gen8_make_rpcs(struct drm_i915_private *i915, struct intel_sseu *ctx_sseu);
#endif /* _INTEL_LRC_H_ */
diff --git a/drivers/gpu/drm/i915/selftests/intel_lrc.c b/drivers/gpu/drm/i915/selftests/intel_lrc.c
index 9e871eb0bfb1..6df033960350 100644
--- a/drivers/gpu/drm/i915/selftests/intel_lrc.c
+++ b/drivers/gpu/drm/i915/selftests/intel_lrc.c
@@ -10,6 +10,7 @@
#include "../i915_selftest.h"
#include "igt_flush_test.h"
+#include "igt_live_test.h"
#include "igt_spinner.h"
#include "i915_random.h"
@@ -1057,6 +1058,169 @@ static int live_preempt_smoke(void *arg)
return err;
}
+static int nop_virtual_engine(struct drm_i915_private *i915,
+ struct intel_engine_cs **siblings,
+ unsigned int nsibling,
+ unsigned int nctx,
+ unsigned int flags)
+#define CHAIN BIT(0)
+{
+ IGT_TIMEOUT(end_time);
+ struct i915_request *request[16];
+ struct i915_gem_context *ctx[16];
+ struct intel_engine_cs *ve[16];
+ unsigned long n, prime, nc;
+ struct igt_live_test t;
+ ktime_t times[2] = {};
+ int err;
+
+ GEM_BUG_ON(!nctx || nctx > ARRAY_SIZE(ctx));
+
+ for (n = 0; n < nctx; n++) {
+ ctx[n] = kernel_context(i915);
+ if (!ctx[n])
+ return -ENOMEM;
+
+ ve[n] = intel_execlists_create_virtual(ctx[n],
+ siblings, nsibling);
+ if (IS_ERR(ve[n]))
+ return PTR_ERR(ve[n]);
+ }
+
+ err = igt_live_test_begin(&t, i915, __func__, ve[0]->name);
+ if (err)
+ goto out;
+
+ for_each_prime_number_from(prime, 1, 8192) {
+ times[1] = ktime_get_raw();
+
+ if (flags & CHAIN) {
+ for (nc = 0; nc < nctx; nc++) {
+ for (n = 0; n < prime; n++) {
+ request[nc] =
+ i915_request_alloc(ve[nc], ctx[nc]);
+ if (IS_ERR(request[nc])) {
+ err = PTR_ERR(request[nc]);
+ goto out;
+ }
+
+ i915_request_add(request[nc]);
+ }
+ }
+ } else {
+ for (n = 0; n < prime; n++) {
+ for (nc = 0; nc < nctx; nc++) {
+ request[nc] =
+ i915_request_alloc(ve[nc], ctx[nc]);
+ if (IS_ERR(request[nc])) {
+ err = PTR_ERR(request[nc]);
+ goto out;
+ }
+
+ i915_request_add(request[nc]);
+ }
+ }
+ }
+
+ for (nc = 0; nc < nctx; nc++) {
+ if (i915_request_wait(request[nc],
+ I915_WAIT_LOCKED,
+ HZ / 10) < 0) {
+ pr_err("%s(%s): wait for %llx:%lld timed out\n",
+ __func__, ve[0]->name,
+ request[nc]->fence.context,
+ request[nc]->fence.seqno);
+
+ GEM_TRACE("%s(%s) failed at request %llx:%lld\n",
+ __func__, ve[0]->name,
+ request[nc]->fence.context,
+ request[nc]->fence.seqno);
+ GEM_TRACE_DUMP();
+ i915_gem_set_wedged(i915);
+ break;
+ }
+ }
+
+ times[1] = ktime_sub(ktime_get_raw(), times[1]);
+ if (prime == 1)
+ times[0] = times[1];
+
+ if (__igt_timeout(end_time, NULL))
+ break;
+ }
+
+ err = igt_live_test_end(&t);
+ if (err)
+ goto out;
+
+ pr_info("Requestx%d latencies on %s: 1 = %lluns, %lu = %lluns\n",
+ nctx, ve[0]->name, ktime_to_ns(times[0]),
+ prime, div64_u64(ktime_to_ns(times[1]), prime));
+
+out:
+ if (igt_flush_test(i915, I915_WAIT_LOCKED))
+ err = -EIO;
+
+ for (nc = 0; nc < nctx; nc++) {
+ intel_virtual_engine_destroy(ve[nc]);
+ kernel_context_close(ctx[nc]);
+ }
+ return err;
+}
+
+static int live_virtual_engine(void *arg)
+{
+ struct drm_i915_private *i915 = arg;
+ struct intel_engine_cs *siblings[MAX_ENGINE_INSTANCE + 1];
+ struct intel_engine_cs *engine;
+ enum intel_engine_id id;
+ unsigned int class, inst;
+ int err = -ENODEV;
+
+ if (USES_GUC_SUBMISSION(i915))
+ return 0;
+
+ mutex_lock(&i915->drm.struct_mutex);
+
+ for_each_engine(engine, i915, id) {
+ err = nop_virtual_engine(i915, &engine, 1, 1, 0);
+ if (err) {
+ pr_err("Failed to wrap engine %s: err=%d\n",
+ engine->name, err);
+ goto out_unlock;
+ }
+ }
+
+ for (class = 0; class <= MAX_ENGINE_CLASS; class++) {
+ int nsibling, n;
+
+ nsibling = 0;
+ for (inst = 0; inst <= MAX_ENGINE_INSTANCE; inst++) {
+ if (!i915->engine_class[class][inst])
+ break;
+
+ siblings[nsibling++] = i915->engine_class[class][inst];
+ }
+ if (nsibling < 2)
+ continue;
+
+ for (n = 1; n <= nsibling + 1; n++) {
+ err = nop_virtual_engine(i915, siblings, nsibling,
+ n, 0);
+ if (err)
+ goto out_unlock;
+ }
+
+ err = nop_virtual_engine(i915, siblings, nsibling, n, CHAIN);
+ if (err)
+ goto out_unlock;
+ }
+
+out_unlock:
+ mutex_unlock(&i915->drm.struct_mutex);
+ return err;
+}
+
int intel_execlists_live_selftests(struct drm_i915_private *i915)
{
static const struct i915_subtest tests[] = {
@@ -1068,6 +1232,7 @@ int intel_execlists_live_selftests(struct drm_i915_private *i915)
SUBTEST(live_chain_preempt),
SUBTEST(live_preempt_hang),
SUBTEST(live_preempt_smoke),
+ SUBTEST(live_virtual_engine),
};
if (!HAS_EXECLISTS(i915))
diff --git a/include/uapi/drm/i915_drm.h b/include/uapi/drm/i915_drm.h
index 8ef6d60929c6..9c94c037d13b 100644
--- a/include/uapi/drm/i915_drm.h
+++ b/include/uapi/drm/i915_drm.h
@@ -127,6 +127,7 @@ enum drm_i915_gem_engine_class {
};
#define I915_ENGINE_CLASS_INVALID_NONE -1
+#define I915_ENGINE_CLASS_INVALID_VIRTUAL 0
/**
* DOC: perf_events exposed by i915 through /sys/bus/event_sources/drivers/i915
@@ -1598,8 +1599,37 @@ struct drm_i915_gem_context_param_sseu {
__u32 rsvd;
};
+/*
+ * i915_context_engines_load_balance:
+ *
+ * Enable load balancing across this set of engines.
+ *
+ * Into the I915_EXEC_DEFAULT slot [0], a virtual engine is created that when
+ * used will proxy the execbuffer request onto one of the set of engines
+ * in such a way as to distribute the load evenly across the set.
+ *
+ * The set of engines must be compatible (e.g. the same HW class) as they
+ * will share the same logical GPU context and ring.
+ *
+ * To intermix rendering with the virtual engine and direct rendering onto
+ * the backing engines (bypassing the load balancing proxy), the context must
+ * be defined to use a single timeline for all engines.
+ */
+struct i915_context_engines_load_balance {
+ struct i915_user_extension base;
+
+ __u16 engine_index;
+ __u16 mbz16; /* reserved for future use; must be zero */
+ __u32 flags; /* all undefined flags must be zero */
+
+ __u64 engines_mask; /* selection mask of engines[] */
+
+ __u64 mbz64[4]; /* reserved for future use; must be zero */
+};
+
struct i915_context_param_engines {
__u64 extensions; /* linked chain of extension blocks, 0 terminates */
+#define I915_CONTEXT_ENGINES_EXT_LOAD_BALANCE 0
struct {
__u16 engine_class; /* see enum drm_i915_gem_engine_class */
Regards,
Tvrtko
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