On Wed, Jun 9, 2021 at 6:28 AM Daniel Vetter <daniel@xxxxxxxx> wrote:
>
> On Tue, Jun 08, 2021 at 11:35:58PM -0500, Jason Ekstrand wrote:
> > The current context uAPI allows for two methods of setting context
> > parameters: SET_CONTEXT_PARAM and CONTEXT_CREATE_EXT_SETPARAM. The
> > former is allowed to be called at any time while the later happens as
> > part of GEM_CONTEXT_CREATE. Currently, everything settable via one is
> > settable via the other. While some params are fairly simple and setting
> > them on a live context is harmless such the context priority, others are
> > far trickier such as the VM or the set of engines. In order to swap out
> > the VM, for instance, we have to delay until all current in-flight work
> > is complete, swap in the new VM, and then continue. This leads to a
> > plethora of potential race conditions we'd really rather avoid.
> >
> > Unfortunately, both methods of setting the VM and the engine set are in
> > active use today so we can't simply disallow setting the VM or engine
> > set vial SET_CONTEXT_PARAM. In order to work around this wart, this
> > commit adds a proto-context struct which contains all the context create
> > parameters.
> >
> > v2 (Daniel Vetter):
> > - Better commit message
> > - Use __set/clear_bit instead of set/clear_bit because there's no race
> > and we don't need the atomics
> >
> > v3 (Daniel Vetter):
> > - Use manual bitops and BIT() instead of __set_bit
> >
> > v4 (Daniel Vetter):
> > - Add a changelog to the commit message
> > - Better hyperlinking in docs
> > - Create the default PPGTT in i915_gem_create_context
> >
> > Signed-off-by: Jason Ekstrand <jason@xxxxxxxxxxxxxx>
> > ---
> > drivers/gpu/drm/i915/gem/i915_gem_context.c | 124 +++++++++++++++---
> > .../gpu/drm/i915/gem/i915_gem_context_types.h | 22 ++++
> > .../gpu/drm/i915/gem/selftests/mock_context.c | 16 ++-
> > 3 files changed, 145 insertions(+), 17 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/gem/i915_gem_context.c b/drivers/gpu/drm/i915/gem/i915_gem_context.c
> > index f9a6eac78c0ae..b5d8c1ff5d7b3 100644
> > --- a/drivers/gpu/drm/i915/gem/i915_gem_context.c
> > +++ b/drivers/gpu/drm/i915/gem/i915_gem_context.c
> > @@ -191,6 +191,83 @@ static int validate_priority(struct drm_i915_private *i915,
> > return 0;
> > }
> >
> > +static void proto_context_close(struct i915_gem_proto_context *pc)
> > +{
> > + if (pc->vm)
> > + i915_vm_put(pc->vm);
> > + kfree(pc);
> > +}
> > +
> > +static int proto_context_set_persistence(struct drm_i915_private *i915,
> > + struct i915_gem_proto_context *pc,
> > + bool persist)
> > +{
> > + if (persist) {
> > + /*
> > + * 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->params.enable_hangcheck)
> > + return -EINVAL;
> > +
> > + pc->user_flags |= BIT(UCONTEXT_PERSISTENCE);
> > + } else {
> > + /* To cancel a context we use "preempt-to-idle" */
> > + if (!(i915->caps.scheduler & I915_SCHEDULER_CAP_PREEMPTION))
> > + return -ENODEV;
> > +
> > + /*
> > + * If the cancel fails, we then need to reset, cleanly!
> > + *
> > + * If the per-engine reset fails, all hope is lost! We resort
> > + * to a full GPU reset in that unlikely case, but realistically
> > + * if the engine could not reset, the full reset does not fare
> > + * much better. The damage has been done.
> > + *
> > + * However, if we cannot reset an engine by itself, we cannot
> > + * cleanup a hanging persistent context without causing
> > + * colateral damage, and we should not pretend we can by
> > + * exposing the interface.
> > + */
> > + if (!intel_has_reset_engine(&i915->gt))
> > + return -ENODEV;
> > +
> > + pc->user_flags &= ~BIT(UCONTEXT_PERSISTENCE);
> > + }
> > +
> > + return 0;
> > +}
> > +
> > +static struct i915_gem_proto_context *
> > +proto_context_create(struct drm_i915_private *i915, unsigned int flags)
> > +{
> > + struct i915_gem_proto_context *pc, *err;
> > +
> > + pc = kzalloc(sizeof(*pc), GFP_KERNEL);
> > + if (!pc)
> > + return ERR_PTR(-ENOMEM);
> > +
> > + pc->user_flags = BIT(UCONTEXT_BANNABLE) |
> > + BIT(UCONTEXT_RECOVERABLE);
> > + proto_context_set_persistence(i915, pc, true);
>
> I think we're down to the bikeshed here that I think should be open-coded
> for clarity of what exactly is going on. But maybe better in a distinct
> patch.
Nope. I just failed at rebasing. :-) I put it in the 2nd big
proto-ctx patch instead of this one. Should be fixed now.
> Reviewed-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
Thanks!
> > + pc->sched.priority = I915_PRIORITY_NORMAL;
> > +
> > + if (flags & I915_CONTEXT_CREATE_FLAGS_SINGLE_TIMELINE) {
> > + if (!HAS_EXECLISTS(i915)) {
> > + err = ERR_PTR(-EINVAL);
> > + goto proto_close;
> > + }
> > + pc->single_timeline = true;
> > + }
> > +
> > + return pc;
> > +
> > +proto_close:
> > + proto_context_close(pc);
> > + return err;
> > +}
> > +
> > static struct i915_address_space *
> > context_get_vm_rcu(struct i915_gem_context *ctx)
> > {
> > @@ -660,7 +737,8 @@ static int __context_set_persistence(struct i915_gem_context *ctx, bool state)
> > }
> >
> > static struct i915_gem_context *
> > -__create_context(struct drm_i915_private *i915)
> > +__create_context(struct drm_i915_private *i915,
> > + const struct i915_gem_proto_context *pc)
> > {
> > struct i915_gem_context *ctx;
> > struct i915_gem_engines *e;
> > @@ -673,7 +751,7 @@ __create_context(struct drm_i915_private *i915)
> >
> > kref_init(&ctx->ref);
> > ctx->i915 = i915;
> > - ctx->sched.priority = I915_PRIORITY_NORMAL;
> > + ctx->sched = pc->sched;
> > mutex_init(&ctx->mutex);
> > INIT_LIST_HEAD(&ctx->link);
> >
> > @@ -696,9 +774,7 @@ __create_context(struct drm_i915_private *i915)
> > * is no remap info, it will be a NOP. */
> > ctx->remap_slice = ALL_L3_SLICES(i915);
> >
> > - i915_gem_context_set_bannable(ctx);
> > - i915_gem_context_set_recoverable(ctx);
> > - __context_set_persistence(ctx, true /* cgroup hook? */);
> > + ctx->user_flags = pc->user_flags;
> >
> > for (i = 0; i < ARRAY_SIZE(ctx->hang_timestamp); i++)
> > ctx->hang_timestamp[i] = jiffies - CONTEXT_FAST_HANG_JIFFIES;
> > @@ -786,20 +862,22 @@ static void __assign_ppgtt(struct i915_gem_context *ctx,
> > }
> >
> > static struct i915_gem_context *
> > -i915_gem_create_context(struct drm_i915_private *i915, unsigned int flags)
> > +i915_gem_create_context(struct drm_i915_private *i915,
> > + const struct i915_gem_proto_context *pc)
> > {
> > struct i915_gem_context *ctx;
> > int ret;
> >
> > - if (flags & I915_CONTEXT_CREATE_FLAGS_SINGLE_TIMELINE &&
> > - !HAS_EXECLISTS(i915))
> > - return ERR_PTR(-EINVAL);
> > -
> > - ctx = __create_context(i915);
> > + ctx = __create_context(i915, pc);
> > if (IS_ERR(ctx))
> > return ctx;
> >
> > - if (HAS_FULL_PPGTT(i915)) {
> > + if (pc->vm) {
> > + /* __assign_ppgtt() requires this mutex to be held */
> > + mutex_lock(&ctx->mutex);
> > + __assign_ppgtt(ctx, pc->vm);
> > + mutex_unlock(&ctx->mutex);
> > + } else if (HAS_FULL_PPGTT(i915)) {
> > struct i915_ppgtt *ppgtt;
> >
> > ppgtt = i915_ppgtt_create(&i915->gt);
> > @@ -810,14 +888,16 @@ i915_gem_create_context(struct drm_i915_private *i915, unsigned int flags)
> > return ERR_CAST(ppgtt);
> > }
> >
> > + /* __assign_ppgtt() requires this mutex to be held */
> > mutex_lock(&ctx->mutex);
> > __assign_ppgtt(ctx, &ppgtt->vm);
> > mutex_unlock(&ctx->mutex);
> >
> > + /* __assign_ppgtt() takes another reference for us */
> > i915_vm_put(&ppgtt->vm);
> > }
> >
> > - if (flags & I915_CONTEXT_CREATE_FLAGS_SINGLE_TIMELINE) {
> > + if (pc->single_timeline) {
> > ret = drm_syncobj_create(&ctx->syncobj,
> > DRM_SYNCOBJ_CREATE_SIGNALED,
> > NULL);
> > @@ -883,6 +963,7 @@ int i915_gem_context_open(struct drm_i915_private *i915,
> > struct drm_file *file)
> > {
> > struct drm_i915_file_private *file_priv = file->driver_priv;
> > + struct i915_gem_proto_context *pc;
> > struct i915_gem_context *ctx;
> > int err;
> > u32 id;
> > @@ -892,7 +973,14 @@ int i915_gem_context_open(struct drm_i915_private *i915,
> > /* 0 reserved for invalid/unassigned ppgtt */
> > xa_init_flags(&file_priv->vm_xa, XA_FLAGS_ALLOC1);
> >
> > - ctx = i915_gem_create_context(i915, 0);
> > + pc = proto_context_create(i915, 0);
> > + if (IS_ERR(pc)) {
> > + err = PTR_ERR(pc);
> > + goto err;
> > + }
> > +
> > + ctx = i915_gem_create_context(i915, pc);
> > + proto_context_close(pc);
> > if (IS_ERR(ctx)) {
> > err = PTR_ERR(ctx);
> > goto err;
> > @@ -1884,6 +1972,7 @@ int i915_gem_context_create_ioctl(struct drm_device *dev, void *data,
> > {
> > struct drm_i915_private *i915 = to_i915(dev);
> > struct drm_i915_gem_context_create_ext *args = data;
> > + struct i915_gem_proto_context *pc;
> > struct create_ext ext_data;
> > int ret;
> > u32 id;
> > @@ -1906,7 +1995,12 @@ int i915_gem_context_create_ioctl(struct drm_device *dev, void *data,
> > return -EIO;
> > }
> >
> > - ext_data.ctx = i915_gem_create_context(i915, args->flags);
> > + pc = proto_context_create(i915, args->flags);
> > + if (IS_ERR(pc))
> > + return PTR_ERR(pc);
> > +
> > + ext_data.ctx = i915_gem_create_context(i915, pc);
> > + proto_context_close(pc);
> > if (IS_ERR(ext_data.ctx))
> > return PTR_ERR(ext_data.ctx);
> >
> > 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 5f0673a2129f9..e0bdf3e298a6a 100644
> > --- a/drivers/gpu/drm/i915/gem/i915_gem_context_types.h
> > +++ b/drivers/gpu/drm/i915/gem/i915_gem_context_types.h
> > @@ -66,6 +66,28 @@ struct i915_gem_engines_iter {
> > const struct i915_gem_engines *engines;
> > };
> >
> > +/**
> > + * struct i915_gem_proto_context - prototype context
> > + *
> > + * The struct i915_gem_proto_context represents the creation parameters for
> > + * a struct i915_gem_context. This is used to gather parameters provided
> > + * either through creation flags or via SET_CONTEXT_PARAM so that, when we
> > + * create the final i915_gem_context, those parameters can be immutable.
> > + */
> > +struct i915_gem_proto_context {
> > + /** @vm: See &i915_gem_context.vm */
> > + struct i915_address_space *vm;
> > +
> > + /** @user_flags: See &i915_gem_context.user_flags */
> > + unsigned long user_flags;
> > +
> > + /** @sched: See &i915_gem_context.sched */
> > + struct i915_sched_attr sched;
> > +
> > + /** @single_timeline: See See &i915_gem_context.syncobj */
> > + bool single_timeline;
> > +};
> > +
> > /**
> > * struct i915_gem_context - client state
> > *
> > diff --git a/drivers/gpu/drm/i915/gem/selftests/mock_context.c b/drivers/gpu/drm/i915/gem/selftests/mock_context.c
> > index 51b5a3421b400..e0f512ef7f3c6 100644
> > --- a/drivers/gpu/drm/i915/gem/selftests/mock_context.c
> > +++ b/drivers/gpu/drm/i915/gem/selftests/mock_context.c
> > @@ -80,11 +80,17 @@ void mock_init_contexts(struct drm_i915_private *i915)
> > struct i915_gem_context *
> > live_context(struct drm_i915_private *i915, struct file *file)
> > {
> > + struct i915_gem_proto_context *pc;
> > struct i915_gem_context *ctx;
> > int err;
> > u32 id;
> >
> > - ctx = i915_gem_create_context(i915, 0);
> > + pc = proto_context_create(i915, 0);
> > + if (IS_ERR(pc))
> > + return ERR_CAST(pc);
> > +
> > + ctx = i915_gem_create_context(i915, pc);
> > + proto_context_close(pc);
> > if (IS_ERR(ctx))
> > return ctx;
> >
> > @@ -142,8 +148,14 @@ struct i915_gem_context *
> > kernel_context(struct drm_i915_private *i915)
> > {
> > struct i915_gem_context *ctx;
> > + struct i915_gem_proto_context *pc;
> > +
> > + pc = proto_context_create(i915, 0);
> > + if (IS_ERR(pc))
> > + return ERR_CAST(pc);
> >
> > - ctx = i915_gem_create_context(i915, 0);
> > + ctx = i915_gem_create_context(i915, pc);
> > + proto_context_close(pc);
> > if (IS_ERR(ctx))
> > return ctx;
> >
> > --
> > 2.31.1
> >
> > _______________________________________________
> > Intel-gfx mailing list
> > Intel-gfx@xxxxxxxxxxxxxxxxxxxxx
> > https://lists.freedesktop.org/mailman/listinfo/intel-gfx
>
> --
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch
