[PATCH 08/21] drm/i915/gem: Disallow bonding of virtual engines
Jason Ekstrand
jason at jlekstrand.net
Tue Apr 27 13:51:08 UTC 2021
On Fri, Apr 23, 2021 at 5:31 PM Jason Ekstrand <jason at jlekstrand.net> wrote:
>
> This adds a bunch of complexity which the media driver has never
> actually used. The media driver does technically bond a balanced engine
> to another engine but the balanced engine only has one engine in the
> sibling set. This doesn't actually result in a virtual engine.
>
> Unless some userspace badly wants it, there's no good reason to support
> this case. This makes I915_CONTEXT_ENGINES_EXT_BOND a total no-op. We
> leave the validation code in place in case we ever decide we want to do
> something interesting with the bonding information.
>
> Signed-off-by: Jason Ekstrand <jason at jlekstrand.net>
> ---
> drivers/gpu/drm/i915/gem/i915_gem_context.c | 18 +-
> .../gpu/drm/i915/gem/i915_gem_execbuffer.c | 2 +-
> drivers/gpu/drm/i915/gt/intel_engine_types.h | 7 -
> .../drm/i915/gt/intel_execlists_submission.c | 100 --------
> .../drm/i915/gt/intel_execlists_submission.h | 4 -
> drivers/gpu/drm/i915/gt/selftest_execlists.c | 229 ------------------
> 6 files changed, 7 insertions(+), 353 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_context.c b/drivers/gpu/drm/i915/gem/i915_gem_context.c
> index e8179918fa306..5f8d0faf783aa 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_context.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_context.c
> @@ -1553,6 +1553,12 @@ set_engines__bond(struct i915_user_extension __user *base, void *data)
> }
> virtual = set->engines->engines[idx]->engine;
>
> + if (intel_engine_is_virtual(virtual)) {
> + drm_dbg(&i915->drm,
> + "Bonding with virtual engines not allowed\n");
> + return -EINVAL;
> + }
> +
> err = check_user_mbz(&ext->flags);
> if (err)
> return err;
> @@ -1593,18 +1599,6 @@ set_engines__bond(struct i915_user_extension __user *base, void *data)
> n, ci.engine_class, ci.engine_instance);
> return -EINVAL;
> }
> -
> - /*
> - * A non-virtual engine has no siblings to choose between; and
> - * a submit fence will always be directed to the one engine.
> - */
> - if (intel_engine_is_virtual(virtual)) {
> - err = intel_virtual_engine_attach_bond(virtual,
> - master,
> - bond);
> - if (err)
> - return err;
> - }
> }
>
> return 0;
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
> index d640bba6ad9ab..efb2fa3522a42 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
> @@ -3474,7 +3474,7 @@ i915_gem_do_execbuffer(struct drm_device *dev,
> if (args->flags & I915_EXEC_FENCE_SUBMIT)
> err = i915_request_await_execution(eb.request,
> in_fence,
> - eb.engine->bond_execute);
> + NULL);
> else
> err = i915_request_await_dma_fence(eb.request,
> in_fence);
> diff --git a/drivers/gpu/drm/i915/gt/intel_engine_types.h b/drivers/gpu/drm/i915/gt/intel_engine_types.h
> index 883bafc449024..68cfe5080325c 100644
> --- a/drivers/gpu/drm/i915/gt/intel_engine_types.h
> +++ b/drivers/gpu/drm/i915/gt/intel_engine_types.h
> @@ -446,13 +446,6 @@ struct intel_engine_cs {
> */
> void (*submit_request)(struct i915_request *rq);
>
> - /*
> - * Called on signaling of a SUBMIT_FENCE, passing along the signaling
> - * request down to the bonded pairs.
> - */
> - void (*bond_execute)(struct i915_request *rq,
> - struct dma_fence *signal);
> -
> /*
> * Call when the priority on a request has changed and it and its
> * dependencies may need rescheduling. Note the request itself may
> diff --git a/drivers/gpu/drm/i915/gt/intel_execlists_submission.c b/drivers/gpu/drm/i915/gt/intel_execlists_submission.c
> index de124870af44d..b6e2b59f133b7 100644
> --- a/drivers/gpu/drm/i915/gt/intel_execlists_submission.c
> +++ b/drivers/gpu/drm/i915/gt/intel_execlists_submission.c
> @@ -181,18 +181,6 @@ struct virtual_engine {
> int prio;
> } nodes[I915_NUM_ENGINES];
>
> - /*
> - * Keep track of bonded pairs -- restrictions upon on our selection
> - * of physical engines any particular request may be submitted to.
> - * If we receive a submit-fence from a master engine, we will only
> - * use one of sibling_mask physical engines.
> - */
> - struct ve_bond {
> - const struct intel_engine_cs *master;
> - intel_engine_mask_t sibling_mask;
> - } *bonds;
> - unsigned int num_bonds;
> -
> /* And finally, which physical engines this virtual engine maps onto. */
> unsigned int num_siblings;
> struct intel_engine_cs *siblings[];
> @@ -3307,7 +3295,6 @@ static void rcu_virtual_context_destroy(struct work_struct *wrk)
> intel_breadcrumbs_free(ve->base.breadcrumbs);
> intel_engine_free_request_pool(&ve->base);
>
> - kfree(ve->bonds);
> kfree(ve);
> }
>
> @@ -3560,42 +3547,6 @@ static void virtual_submit_request(struct i915_request *rq)
> spin_unlock_irqrestore(&ve->base.active.lock, flags);
> }
>
> -static struct ve_bond *
> -virtual_find_bond(struct virtual_engine *ve,
> - const struct intel_engine_cs *master)
> -{
> - int i;
> -
> - for (i = 0; i < ve->num_bonds; i++) {
> - if (ve->bonds[i].master == master)
> - return &ve->bonds[i];
> - }
> -
> - return NULL;
> -}
> -
> -static void
> -virtual_bond_execute(struct i915_request *rq, struct dma_fence *signal)
> -{
> - struct virtual_engine *ve = to_virtual_engine(rq->engine);
> - intel_engine_mask_t allowed, exec;
> - struct ve_bond *bond;
> -
> - allowed = ~to_request(signal)->engine->mask;
> -
> - bond = virtual_find_bond(ve, to_request(signal)->engine);
> - if (bond)
> - allowed &= bond->sibling_mask;
> -
> - /* Restrict the bonded request to run on only the available engines */
> - exec = READ_ONCE(rq->execution_mask);
> - while (!try_cmpxchg(&rq->execution_mask, &exec, exec & allowed))
> - ;
> -
> - /* Prevent the master from being re-run on the bonded engines */
> - to_request(signal)->execution_mask &= ~allowed;
I sent a v2 of this patch because it turns out I deleted a bit too
much code. This function in particular, has to stay, unfortunately.
When a batch is submitted with a SUBMIT_FENCE, this is used to push
the work onto a different engine than than the one it's supposed to
run in parallel with. This means we can't dead-code this function or
the bond_execution function pointer and related stuff.
--Jason
> -}
> -
> struct intel_context *
> intel_execlists_create_virtual(struct intel_engine_cs **siblings,
> unsigned int count)
> @@ -3649,7 +3600,6 @@ intel_execlists_create_virtual(struct intel_engine_cs **siblings,
>
> ve->base.schedule = i915_schedule;
> ve->base.submit_request = virtual_submit_request;
> - ve->base.bond_execute = virtual_bond_execute;
>
> INIT_LIST_HEAD(virtual_queue(ve));
> ve->base.execlists.queue_priority_hint = INT_MIN;
> @@ -3747,59 +3697,9 @@ intel_execlists_clone_virtual(struct intel_engine_cs *src)
> if (IS_ERR(dst))
> return dst;
>
> - if (se->num_bonds) {
> - struct virtual_engine *de = to_virtual_engine(dst->engine);
> -
> - de->bonds = kmemdup(se->bonds,
> - sizeof(*se->bonds) * se->num_bonds,
> - GFP_KERNEL);
> - if (!de->bonds) {
> - intel_context_put(dst);
> - return ERR_PTR(-ENOMEM);
> - }
> -
> - de->num_bonds = se->num_bonds;
> - }
> -
> return dst;
> }
>
> -int intel_virtual_engine_attach_bond(struct intel_engine_cs *engine,
> - const struct intel_engine_cs *master,
> - const struct intel_engine_cs *sibling)
> -{
> - struct virtual_engine *ve = to_virtual_engine(engine);
> - struct ve_bond *bond;
> - int n;
> -
> - /* Sanity check the sibling is part of the virtual engine */
> - for (n = 0; n < ve->num_siblings; n++)
> - if (sibling == ve->siblings[n])
> - break;
> - if (n == ve->num_siblings)
> - return -EINVAL;
> -
> - bond = virtual_find_bond(ve, master);
> - if (bond) {
> - bond->sibling_mask |= sibling->mask;
> - return 0;
> - }
> -
> - bond = krealloc(ve->bonds,
> - sizeof(*bond) * (ve->num_bonds + 1),
> - GFP_KERNEL);
> - if (!bond)
> - return -ENOMEM;
> -
> - bond[ve->num_bonds].master = master;
> - bond[ve->num_bonds].sibling_mask = sibling->mask;
> -
> - ve->bonds = bond;
> - ve->num_bonds++;
> -
> - return 0;
> -}
> -
> void intel_execlists_show_requests(struct intel_engine_cs *engine,
> struct drm_printer *m,
> void (*show_request)(struct drm_printer *m,
> diff --git a/drivers/gpu/drm/i915/gt/intel_execlists_submission.h b/drivers/gpu/drm/i915/gt/intel_execlists_submission.h
> index fd61dae820e9e..80cec37a56ba9 100644
> --- a/drivers/gpu/drm/i915/gt/intel_execlists_submission.h
> +++ b/drivers/gpu/drm/i915/gt/intel_execlists_submission.h
> @@ -39,10 +39,6 @@ intel_execlists_create_virtual(struct intel_engine_cs **siblings,
> struct intel_context *
> intel_execlists_clone_virtual(struct intel_engine_cs *src);
>
> -int intel_virtual_engine_attach_bond(struct intel_engine_cs *engine,
> - const struct intel_engine_cs *master,
> - const struct intel_engine_cs *sibling);
> -
> bool
> intel_engine_in_execlists_submission_mode(const struct intel_engine_cs *engine);
>
> diff --git a/drivers/gpu/drm/i915/gt/selftest_execlists.c b/drivers/gpu/drm/i915/gt/selftest_execlists.c
> index 1081cd36a2bd3..f03446d587160 100644
> --- a/drivers/gpu/drm/i915/gt/selftest_execlists.c
> +++ b/drivers/gpu/drm/i915/gt/selftest_execlists.c
> @@ -4311,234 +4311,6 @@ static int live_virtual_preserved(void *arg)
> return 0;
> }
>
> -static int bond_virtual_engine(struct intel_gt *gt,
> - unsigned int class,
> - struct intel_engine_cs **siblings,
> - unsigned int nsibling,
> - unsigned int flags)
> -#define BOND_SCHEDULE BIT(0)
> -{
> - struct intel_engine_cs *master;
> - struct i915_request *rq[16];
> - enum intel_engine_id id;
> - struct igt_spinner spin;
> - unsigned long n;
> - int err;
> -
> - /*
> - * A set of bonded requests is intended to be run concurrently
> - * across a number of engines. We use one request per-engine
> - * and a magic fence to schedule each of the bonded requests
> - * at the same time. A consequence of our current scheduler is that
> - * we only move requests to the HW ready queue when the request
> - * becomes ready, that is when all of its prerequisite fences have
> - * been signaled. As one of those fences is the master submit fence,
> - * there is a delay on all secondary fences as the HW may be
> - * currently busy. Equally, as all the requests are independent,
> - * they may have other fences that delay individual request
> - * submission to HW. Ergo, we do not guarantee that all requests are
> - * immediately submitted to HW at the same time, just that if the
> - * rules are abided by, they are ready at the same time as the
> - * first is submitted. Userspace can embed semaphores in its batch
> - * to ensure parallel execution of its phases as it requires.
> - * Though naturally it gets requested that perhaps the scheduler should
> - * take care of parallel execution, even across preemption events on
> - * different HW. (The proper answer is of course "lalalala".)
> - *
> - * With the submit-fence, we have identified three possible phases
> - * of synchronisation depending on the master fence: queued (not
> - * ready), executing, and signaled. The first two are quite simple
> - * and checked below. However, the signaled master fence handling is
> - * contentious. Currently we do not distinguish between a signaled
> - * fence and an expired fence, as once signaled it does not convey
> - * any information about the previous execution. It may even be freed
> - * and hence checking later it may not exist at all. Ergo we currently
> - * do not apply the bonding constraint for an already signaled fence,
> - * as our expectation is that it should not constrain the secondaries
> - * and is outside of the scope of the bonded request API (i.e. all
> - * userspace requests are meant to be running in parallel). As
> - * it imposes no constraint, and is effectively a no-op, we do not
> - * check below as normal execution flows are checked extensively above.
> - *
> - * XXX Is the degenerate handling of signaled submit fences the
> - * expected behaviour for userpace?
> - */
> -
> - GEM_BUG_ON(nsibling >= ARRAY_SIZE(rq) - 1);
> -
> - if (igt_spinner_init(&spin, gt))
> - return -ENOMEM;
> -
> - err = 0;
> - rq[0] = ERR_PTR(-ENOMEM);
> - for_each_engine(master, gt, id) {
> - struct i915_sw_fence fence = {};
> - struct intel_context *ce;
> -
> - if (master->class == class)
> - continue;
> -
> - ce = intel_context_create(master);
> - if (IS_ERR(ce)) {
> - err = PTR_ERR(ce);
> - goto out;
> - }
> -
> - memset_p((void *)rq, ERR_PTR(-EINVAL), ARRAY_SIZE(rq));
> -
> - rq[0] = igt_spinner_create_request(&spin, ce, MI_NOOP);
> - intel_context_put(ce);
> - if (IS_ERR(rq[0])) {
> - err = PTR_ERR(rq[0]);
> - goto out;
> - }
> - i915_request_get(rq[0]);
> -
> - if (flags & BOND_SCHEDULE) {
> - onstack_fence_init(&fence);
> - err = i915_sw_fence_await_sw_fence_gfp(&rq[0]->submit,
> - &fence,
> - GFP_KERNEL);
> - }
> -
> - i915_request_add(rq[0]);
> - if (err < 0)
> - goto out;
> -
> - if (!(flags & BOND_SCHEDULE) &&
> - !igt_wait_for_spinner(&spin, rq[0])) {
> - err = -EIO;
> - goto out;
> - }
> -
> - for (n = 0; n < nsibling; n++) {
> - struct intel_context *ve;
> -
> - ve = intel_execlists_create_virtual(siblings, nsibling);
> - if (IS_ERR(ve)) {
> - err = PTR_ERR(ve);
> - onstack_fence_fini(&fence);
> - goto out;
> - }
> -
> - err = intel_virtual_engine_attach_bond(ve->engine,
> - master,
> - siblings[n]);
> - if (err) {
> - intel_context_put(ve);
> - onstack_fence_fini(&fence);
> - goto out;
> - }
> -
> - err = intel_context_pin(ve);
> - intel_context_put(ve);
> - if (err) {
> - onstack_fence_fini(&fence);
> - goto out;
> - }
> -
> - rq[n + 1] = i915_request_create(ve);
> - intel_context_unpin(ve);
> - if (IS_ERR(rq[n + 1])) {
> - err = PTR_ERR(rq[n + 1]);
> - onstack_fence_fini(&fence);
> - goto out;
> - }
> - i915_request_get(rq[n + 1]);
> -
> - err = i915_request_await_execution(rq[n + 1],
> - &rq[0]->fence,
> - ve->engine->bond_execute);
> - i915_request_add(rq[n + 1]);
> - if (err < 0) {
> - onstack_fence_fini(&fence);
> - goto out;
> - }
> - }
> - onstack_fence_fini(&fence);
> - intel_engine_flush_submission(master);
> - igt_spinner_end(&spin);
> -
> - if (i915_request_wait(rq[0], 0, HZ / 10) < 0) {
> - pr_err("Master request did not execute (on %s)!\n",
> - rq[0]->engine->name);
> - err = -EIO;
> - goto out;
> - }
> -
> - for (n = 0; n < nsibling; n++) {
> - if (i915_request_wait(rq[n + 1], 0,
> - MAX_SCHEDULE_TIMEOUT) < 0) {
> - err = -EIO;
> - goto out;
> - }
> -
> - if (rq[n + 1]->engine != siblings[n]) {
> - pr_err("Bonded request did not execute on target engine: expected %s, used %s; master was %s\n",
> - siblings[n]->name,
> - rq[n + 1]->engine->name,
> - rq[0]->engine->name);
> - err = -EINVAL;
> - goto out;
> - }
> - }
> -
> - for (n = 0; !IS_ERR(rq[n]); n++)
> - i915_request_put(rq[n]);
> - rq[0] = ERR_PTR(-ENOMEM);
> - }
> -
> -out:
> - for (n = 0; !IS_ERR(rq[n]); n++)
> - i915_request_put(rq[n]);
> - if (igt_flush_test(gt->i915))
> - err = -EIO;
> -
> - igt_spinner_fini(&spin);
> - return err;
> -}
> -
> -static int live_virtual_bond(void *arg)
> -{
> - static const struct phase {
> - const char *name;
> - unsigned int flags;
> - } phases[] = {
> - { "", 0 },
> - { "schedule", BOND_SCHEDULE },
> - { },
> - };
> - struct intel_gt *gt = arg;
> - struct intel_engine_cs *siblings[MAX_ENGINE_INSTANCE + 1];
> - unsigned int class;
> - int err;
> -
> - if (intel_uc_uses_guc_submission(>->uc))
> - return 0;
> -
> - for (class = 0; class <= MAX_ENGINE_CLASS; class++) {
> - const struct phase *p;
> - int nsibling;
> -
> - nsibling = select_siblings(gt, class, siblings);
> - if (nsibling < 2)
> - continue;
> -
> - for (p = phases; p->name; p++) {
> - err = bond_virtual_engine(gt,
> - class, siblings, nsibling,
> - p->flags);
> - if (err) {
> - pr_err("%s(%s): failed class=%d, nsibling=%d, err=%d\n",
> - __func__, p->name, class, nsibling, err);
> - return err;
> - }
> - }
> - }
> -
> - return 0;
> -}
> -
> static int reset_virtual_engine(struct intel_gt *gt,
> struct intel_engine_cs **siblings,
> unsigned int nsibling)
> @@ -4712,7 +4484,6 @@ int intel_execlists_live_selftests(struct drm_i915_private *i915)
> SUBTEST(live_virtual_mask),
> SUBTEST(live_virtual_preserved),
> SUBTEST(live_virtual_slice),
> - SUBTEST(live_virtual_bond),
> SUBTEST(live_virtual_reset),
> };
>
> --
> 2.31.1
>
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