Re: [Intel-gfx] [PATCH 16/21] drm/i915/gem: Delay context creation

[Jason Ekstrand <jason@jlekstrand.net>]

On Thu, Apr 29, 2021 at 10:51 AM Daniel Vetter <daniel@ffwll.ch> wrote:
>
> Yeah this needs some text to explain what/why you're doing this, and maybe
> some rough sketch of the locking design.

Yup.  Will add.

>
> On Fri, Apr 23, 2021 at 05:31:26PM -0500, Jason Ekstrand wrote:
> > Signed-off-by: Jason Ekstrand <jason@jlekstrand.net>
> > ---
> >  drivers/gpu/drm/i915/gem/i915_gem_context.c   | 657 ++++++++++++++++--
> >  drivers/gpu/drm/i915/gem/i915_gem_context.h   |   3 +
> >  .../gpu/drm/i915/gem/i915_gem_context_types.h |  26 +
> >  .../gpu/drm/i915/gem/selftests/mock_context.c |   5 +-
> >  drivers/gpu/drm/i915/i915_drv.h               |  17 +-
> >  5 files changed, 648 insertions(+), 60 deletions(-)
>
> So I think the patch split here is a bit unfortunate, because you're
> adding the new vm/engine validation code for proto context here, but the
> old stuff is only removed in the next patches that make vm/engines
> immutable after first use.

Yes, it's very unfortunate.  I'm reworking things now to have a
different split which I think makes more sense but actually separates
the add from the remove even further. :-(

> I think a better split would be if this patch here only has all the
> scaffolding. You already have the EOPNOTSUPP fallback (which I hope gets
> removed), so moving the conversion entirely to later patches should be all
> fine.
>
> Or do I miss something?
>
> I think the only concern I'm seeing is that bisectability might be a bit
> lost, because we finalize the context in some cases in setparam. And if we
> do the conversion in a different order than the one media uses for its
> setparam, then later setparam might fail because the context is finalized
> already. But also
> - it's just bisectability of media functionality I think
> - just check which order media calls CTX_SETPARAM and use that to do the
>   conversion
>
> And we should be fine ... I think?

Before we go down that path, let's what you think of my new ordering.

> Some more thoughts below, but the proto ctx stuff itself looks fine.
>
> >
> > diff --git a/drivers/gpu/drm/i915/gem/i915_gem_context.c b/drivers/gpu/drm/i915/gem/i915_gem_context.c
> > index db9153e0f85a7..aa8e61211924f 100644
> > --- a/drivers/gpu/drm/i915/gem/i915_gem_context.c
> > +++ b/drivers/gpu/drm/i915/gem/i915_gem_context.c
> > @@ -193,8 +193,15 @@ static int validate_priority(struct drm_i915_private *i915,
> >
> >  static void proto_context_close(struct i915_gem_proto_context *pc)
> >  {
> > +     int i;
> > +
> >       if (pc->vm)
> >               i915_vm_put(pc->vm);
> > +     if (pc->user_engines) {
> > +             for (i = 0; i < pc->num_user_engines; i++)
> > +                     kfree(pc->user_engines[i].siblings);
> > +             kfree(pc->user_engines);
> > +     }
> >       kfree(pc);
> >  }
> >
> > @@ -274,12 +281,417 @@ proto_context_create(struct drm_i915_private *i915, unsigned int flags)
> >       proto_context_set_persistence(i915, pc, true);
> >       pc->sched.priority = I915_PRIORITY_NORMAL;
> >
> > +     pc->num_user_engines = -1;
> > +     pc->user_engines = NULL;
> > +
> >       if (flags & I915_CONTEXT_CREATE_FLAGS_SINGLE_TIMELINE)
> >               pc->single_timeline = true;
> >
> >       return pc;
> >  }
> >
> > +static int proto_context_register_locked(struct drm_i915_file_private *fpriv,
> > +                                      struct i915_gem_proto_context *pc,
> > +                                      u32 *id)
> > +{
> > +     int ret;
> > +     void *old;
>
> assert_lock_held just for consistency.

Done.

> > +
> > +     ret = xa_alloc(&fpriv->context_xa, id, NULL, xa_limit_32b, GFP_KERNEL);
> > +     if (ret)
> > +             return ret;
> > +
> > +     old = xa_store(&fpriv->proto_context_xa, *id, pc, GFP_KERNEL);
> > +     if (xa_is_err(old)) {
> > +             xa_erase(&fpriv->context_xa, *id);
> > +             return xa_err(old);
> > +     }
> > +     GEM_BUG_ON(old);
> > +
> > +     return 0;
> > +}
> > +
> > +static int proto_context_register(struct drm_i915_file_private *fpriv,
> > +                               struct i915_gem_proto_context *pc,
> > +                               u32 *id)
> > +{
> > +     int ret;
> > +
> > +     mutex_lock(&fpriv->proto_context_lock);
> > +     ret = proto_context_register_locked(fpriv, pc, id);
> > +     mutex_unlock(&fpriv->proto_context_lock);
> > +
> > +     return ret;
> > +}
> > +
> > +static int set_proto_ctx_vm(struct drm_i915_file_private *fpriv,
> > +                         struct i915_gem_proto_context *pc,
> > +                         const struct drm_i915_gem_context_param *args)
> > +{
> > +     struct i915_address_space *vm;
> > +
> > +     if (args->size)
> > +             return -EINVAL;
> > +
> > +     if (!pc->vm)
> > +             return -ENODEV;
> > +
> > +     if (upper_32_bits(args->value))
> > +             return -ENOENT;
> > +
> > +     rcu_read_lock();
> > +     vm = xa_load(&fpriv->vm_xa, args->value);
> > +     if (vm && !kref_get_unless_zero(&vm->ref))
> > +             vm = NULL;
> > +     rcu_read_unlock();
> > +     if (!vm)
> > +             return -ENOENT;
> > +
> > +     i915_vm_put(pc->vm);
> > +     pc->vm = vm;
> > +
> > +     return 0;
> > +}
> > +
> > +struct set_proto_ctx_engines {
> > +     struct drm_i915_private *i915;
> > +     unsigned num_engines;
> > +     struct i915_gem_proto_engine *engines;
> > +};
> > +
> > +static int
> > +set_proto_ctx_engines_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_proto_ctx_engines *set = data;
> > +     struct drm_i915_private *i915 = set->i915;
> > +     struct intel_engine_cs **siblings;
> > +     u16 num_siblings, idx;
> > +     unsigned int n;
> > +     int err;
> > +
> > +     if (!HAS_EXECLISTS(i915))
> > +             return -ENODEV;
> > +
> > +     if (intel_uc_uses_guc_submission(&i915->gt.uc))
> > +             return -ENODEV; /* not implement yet */
> > +
> > +     if (get_user(idx, &ext->engine_index))
> > +             return -EFAULT;
> > +
> > +     if (idx >= set->num_engines) {
> > +             drm_dbg(&i915->drm, "Invalid placement value, %d >= %d\n",
> > +                     idx, set->num_engines);
> > +             return -EINVAL;
> > +     }
> > +
> > +     idx = array_index_nospec(idx, set->num_engines);
> > +     if (set->engines[idx].type != I915_GEM_ENGINE_TYPE_INVALID) {
> > +             drm_dbg(&i915->drm,
> > +                     "Invalid placement[%d], already occupied\n", idx);
> > +             return -EEXIST;
> > +     }
> > +
> > +     if (get_user(num_siblings, &ext->num_siblings))
> > +             return -EFAULT;
> > +
> > +     err = check_user_mbz(&ext->flags);
> > +     if (err)
> > +             return err;
> > +
> > +     err = check_user_mbz(&ext->mbz64);
> > +     if (err)
> > +             return err;
> > +
> > +     if (num_siblings == 0)
> > +             return 0;
> > +
> > +     siblings = kmalloc_array(num_siblings, sizeof(*siblings), GFP_KERNEL);
> > +     if (!siblings)
> > +             return -ENOMEM;
> > +
> > +     for (n = 0; n < num_siblings; n++) {
> > +             struct i915_engine_class_instance ci;
> > +
> > +             if (copy_from_user(&ci, &ext->engines[n], sizeof(ci))) {
> > +                     err = -EFAULT;
> > +                     goto err_siblings;
> > +             }
> > +
> > +             siblings[n] = intel_engine_lookup_user(i915,
> > +                                                    ci.engine_class,
> > +                                                    ci.engine_instance);
> > +             if (!siblings[n]) {
> > +                     drm_dbg(&i915->drm,
> > +                             "Invalid sibling[%d]: { class:%d, inst:%d }\n",
> > +                             n, ci.engine_class, ci.engine_instance);
> > +                     err = -EINVAL;
> > +                     goto err_siblings;
> > +             }
> > +     }
> > +
> > +     if (num_siblings == 1) {
> > +             set->engines[idx].type = I915_GEM_ENGINE_TYPE_PHYSICAL;
> > +             set->engines[idx].engine = siblings[0];
> > +             kfree(siblings);
> > +     } else {
> > +             set->engines[idx].type = I915_GEM_ENGINE_TYPE_BALANCED;
> > +             set->engines[idx].num_siblings = num_siblings;
> > +             set->engines[idx].siblings = siblings;
> > +     }
> > +
> > +     return 0;
> > +
> > +err_siblings:
> > +     kfree(siblings);
> > +
> > +     return err;
> > +}
> > +
> > +static int
> > +set_proto_ctx_engines_bond(struct i915_user_extension __user *base, void *data)
> > +{
> > +     struct i915_context_engines_bond __user *ext =
> > +             container_of_user(base, typeof(*ext), base);
> > +     const struct set_proto_ctx_engines *set = data;
> > +     struct drm_i915_private *i915 = set->i915;
> > +     struct i915_engine_class_instance ci;
> > +     struct intel_engine_cs *master;
> > +     u16 idx, num_bonds;
> > +     int err, n;
> > +
> > +     if (get_user(idx, &ext->virtual_index))
> > +             return -EFAULT;
> > +
> > +     if (idx >= set->num_engines) {
> > +             drm_dbg(&i915->drm,
> > +                     "Invalid index for virtual engine: %d >= %d\n",
> > +                     idx, set->num_engines);
> > +             return -EINVAL;
> > +     }
> > +
> > +     idx = array_index_nospec(idx, set->num_engines);
> > +     if (set->engines[idx].type == I915_GEM_ENGINE_TYPE_INVALID) {
> > +             drm_dbg(&i915->drm, "Invalid engine at %d\n", idx);
> > +             return -EINVAL;
> > +     }
> > +
> > +     if (set->engines[idx].type != I915_GEM_ENGINE_TYPE_PHYSICAL) {
> > +             drm_dbg(&i915->drm,
> > +                     "Bonding with virtual engines not allowed\n");
> > +             return -EINVAL;
> > +     }
> > +
> > +     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 (copy_from_user(&ci, &ext->master, sizeof(ci)))
> > +             return -EFAULT;
> > +
> > +     master = intel_engine_lookup_user(i915,
> > +                                       ci.engine_class,
> > +                                       ci.engine_instance);
> > +     if (!master) {
> > +             drm_dbg(&i915->drm,
> > +                     "Unrecognised master engine: { class:%u, instance:%u }\n",
> > +                     ci.engine_class, ci.engine_instance);
> > +             return -EINVAL;
> > +     }
> > +
> > +     if (get_user(num_bonds, &ext->num_bonds))
> > +             return -EFAULT;
> > +
> > +     for (n = 0; n < num_bonds; n++) {
> > +             struct intel_engine_cs *bond;
> > +
> > +             if (copy_from_user(&ci, &ext->engines[n], sizeof(ci)))
> > +                     return -EFAULT;
> > +
> > +             bond = intel_engine_lookup_user(i915,
> > +                                             ci.engine_class,
> > +                                             ci.engine_instance);
> > +             if (!bond) {
> > +                     drm_dbg(&i915->drm,
> > +                             "Unrecognised engine[%d] for bonding: { class:%d, instance: %d }\n",
> > +                             n, ci.engine_class, ci.engine_instance);
> > +                     return -EINVAL;
> > +             }
> > +     }
> > +
> > +     return 0;
> > +}
> > +
> > +static const i915_user_extension_fn set_proto_ctx_engines_extensions[] = {
> > +     [I915_CONTEXT_ENGINES_EXT_LOAD_BALANCE] = set_proto_ctx_engines_balance,
> > +     [I915_CONTEXT_ENGINES_EXT_BOND] = set_proto_ctx_engines_bond,
> > +};
> > +
> > +static int set_proto_ctx_engines(struct drm_i915_file_private *fpriv,
> > +                              struct i915_gem_proto_context *pc,
> > +                              const struct drm_i915_gem_context_param *args)
> > +{
> > +     struct drm_i915_private *i915 = fpriv->dev_priv;
> > +     struct set_proto_ctx_engines set = { .i915 = i915 };
> > +     struct i915_context_param_engines __user *user =
> > +             u64_to_user_ptr(args->value);
> > +     unsigned int n;
> > +     u64 extensions;
> > +     int err;
> > +
> > +     if (!args->size) {
> > +             kfree(pc->user_engines);
> > +             pc->num_user_engines = -1;
> > +             pc->user_engines = NULL;
> > +             return 0;
> > +     }
> > +
> > +     BUILD_BUG_ON(!IS_ALIGNED(sizeof(*user), sizeof(*user->engines)));
> > +     if (args->size < sizeof(*user) ||
> > +         !IS_ALIGNED(args->size, sizeof(*user->engines))) {
> > +             drm_dbg(&i915->drm, "Invalid size for engine array: %d\n",
> > +                     args->size);
> > +             return -EINVAL;
> > +     }
> > +
> > +     set.num_engines = (args->size - sizeof(*user)) / sizeof(*user->engines);
> > +     if (set.num_engines > I915_EXEC_RING_MASK + 1)
> > +             return -EINVAL;
> > +
> > +     set.engines = kmalloc_array(set.num_engines, sizeof(*set.engines), GFP_KERNEL);
> > +     if (!set.engines)
> > +             return -ENOMEM;
> > +
> > +     for (n = 0; n < set.num_engines; n++) {
> > +             struct i915_engine_class_instance ci;
> > +             struct intel_engine_cs *engine;
> > +
> > +             if (copy_from_user(&ci, &user->engines[n], sizeof(ci))) {
> > +                     kfree(set.engines);
> > +                     return -EFAULT;
> > +             }
> > +
> > +             memset(&set.engines[n], 0, sizeof(set.engines[n]));
> > +
> > +             if (ci.engine_class == (u16)I915_ENGINE_CLASS_INVALID &&
> > +                 ci.engine_instance == (u16)I915_ENGINE_CLASS_INVALID_NONE)
> > +                     continue;
> > +
> > +             engine = intel_engine_lookup_user(i915,
> > +                                               ci.engine_class,
> > +                                               ci.engine_instance);
> > +             if (!engine) {
> > +                     drm_dbg(&i915->drm,
> > +                             "Invalid engine[%d]: { class:%d, instance:%d }\n",
> > +                             n, ci.engine_class, ci.engine_instance);
> > +                     kfree(set.engines);
> > +                     return -ENOENT;
> > +             }
> > +
> > +             set.engines[n].type = I915_GEM_ENGINE_TYPE_PHYSICAL;
> > +             set.engines[n].engine = engine;
> > +     }
> > +
> > +     err = -EFAULT;
> > +     if (!get_user(extensions, &user->extensions))
> > +             err = i915_user_extensions(u64_to_user_ptr(extensions),
> > +                                        set_proto_ctx_engines_extensions,
> > +                                        ARRAY_SIZE(set_proto_ctx_engines_extensions),
> > +                                        &set);
> > +     if (err) {
> > +             kfree(set.engines);
> > +             return err;
> > +     }
> > +
> > +     kfree(pc->user_engines);
> > +     pc->num_user_engines = set.num_engines;
> > +     pc->user_engines = set.engines;
> > +
> > +     return 0;
> > +}
> > +
> > +static int set_proto_ctx_param(struct drm_i915_file_private *fpriv,
> > +                            struct i915_gem_proto_context *pc,
> > +                            struct drm_i915_gem_context_param *args)
> > +{
> > +     int ret = 0;
> > +
> > +     switch (args->param) {
> > +     case I915_CONTEXT_PARAM_NO_ERROR_CAPTURE:
> > +             if (args->size)
> > +                     ret = -EINVAL;
> > +             else if (args->value)
> > +                     set_bit(UCONTEXT_NO_ERROR_CAPTURE, &pc->user_flags);
>
> Atomic bitops like in previous patches: Pls no :-)

Yup.  Fixed.

> > +             else
> > +                     clear_bit(UCONTEXT_NO_ERROR_CAPTURE, &pc->user_flags);
> > +             break;
> > +
> > +     case I915_CONTEXT_PARAM_BANNABLE:
> > +             if (args->size)
> > +                     ret = -EINVAL;
> > +             else if (!capable(CAP_SYS_ADMIN) && !args->value)
> > +                     ret = -EPERM;
> > +             else if (args->value)
> > +                     set_bit(UCONTEXT_BANNABLE, &pc->user_flags);
> > +             else
> > +                     clear_bit(UCONTEXT_BANNABLE, &pc->user_flags);
> > +             break;
> > +
> > +     case I915_CONTEXT_PARAM_RECOVERABLE:
> > +             if (args->size)
> > +                     ret = -EINVAL;
> > +             else if (args->value)
> > +                     set_bit(UCONTEXT_RECOVERABLE, &pc->user_flags);
> > +             else
> > +                     clear_bit(UCONTEXT_RECOVERABLE, &pc->user_flags);
> > +             break;
> > +
> > +     case I915_CONTEXT_PARAM_PRIORITY:
> > +             ret = validate_priority(fpriv->dev_priv, args);
> > +             if (!ret)
> > +                     pc->sched.priority = args->value;
> > +             break;
> > +
> > +     case I915_CONTEXT_PARAM_SSEU:
> > +             ret = -ENOTSUPP;
> > +             break;
> > +
> > +     case I915_CONTEXT_PARAM_VM:
> > +             ret = set_proto_ctx_vm(fpriv, pc, args);
> > +             break;
> > +
> > +     case I915_CONTEXT_PARAM_ENGINES:
> > +             ret = set_proto_ctx_engines(fpriv, pc, args);
> > +             break;
> > +
> > +     case I915_CONTEXT_PARAM_PERSISTENCE:
> > +             if (args->size)
> > +                     ret = -EINVAL;
> > +             else if (args->value)
> > +                     set_bit(UCONTEXT_PERSISTENCE, &pc->user_flags);
> > +             else
> > +                     clear_bit(UCONTEXT_PERSISTENCE, &pc->user_flags);
> > +             break;
> > +
> > +     case I915_CONTEXT_PARAM_NO_ZEROMAP:
> > +     case I915_CONTEXT_PARAM_BAN_PERIOD:
> > +     case I915_CONTEXT_PARAM_RINGSIZE:
> > +     default:
> > +             ret = -EINVAL;
> > +             break;
> > +     }
> > +
> > +     return ret;
> > +}
> > +
> >  static struct i915_address_space *
> >  context_get_vm_rcu(struct i915_gem_context *ctx)
> >  {
> > @@ -450,6 +862,47 @@ static struct i915_gem_engines *default_engines(struct i915_gem_context *ctx)
> >       return e;
> >  }
> >
> > +static struct i915_gem_engines *user_engines(struct i915_gem_context *ctx,
> > +                                          unsigned int num_engines,
> > +                                          struct i915_gem_proto_engine *pe)
> > +{
> > +     struct i915_gem_engines *e;
> > +     unsigned int n;
> > +
> > +     e = alloc_engines(num_engines);
> > +     for (n = 0; n < num_engines; n++) {
> > +             struct intel_context *ce;
> > +
> > +             switch (pe[n].type) {
> > +             case I915_GEM_ENGINE_TYPE_PHYSICAL:
> > +                     ce = intel_context_create(pe[n].engine);
> > +                     break;
> > +
> > +             case I915_GEM_ENGINE_TYPE_BALANCED:
> > +                     ce = intel_execlists_create_virtual(pe[n].siblings,
> > +                                                         pe[n].num_siblings);
> > +                     break;
> > +
> > +             case I915_GEM_ENGINE_TYPE_INVALID:
> > +             default:
> > +                     GEM_WARN_ON(pe[n].type != I915_GEM_ENGINE_TYPE_INVALID);
> > +                     continue;
> > +             }
> > +
> > +             if (IS_ERR(ce)) {
> > +                     __free_engines(e, n);
> > +                     return ERR_CAST(ce);
> > +             }
> > +
> > +             intel_context_set_gem(ce, ctx);
> > +
> > +             e->engines[n] = ce;
> > +     }
> > +     e->num_engines = num_engines;
> > +
> > +     return e;
> > +}
> > +
> >  void i915_gem_context_release(struct kref *ref)
> >  {
> >       struct i915_gem_context *ctx = container_of(ref, typeof(*ctx), ref);
> > @@ -890,6 +1343,24 @@ i915_gem_create_context(struct drm_i915_private *i915,
> >               mutex_unlock(&ctx->mutex);
> >       }
> >
> > +     if (pc->num_user_engines >= 0) {
> > +             struct i915_gem_engines *engines;
> > +
> > +             engines = user_engines(ctx, pc->num_user_engines,
> > +                                    pc->user_engines);
> > +             if (IS_ERR(engines)) {
> > +                     context_close(ctx);
> > +                     return ERR_CAST(engines);
> > +             }
> > +
> > +             mutex_lock(&ctx->engines_mutex);
> > +             i915_gem_context_set_user_engines(ctx);
> > +             engines = rcu_replace_pointer(ctx->engines, engines, 1);
> > +             mutex_unlock(&ctx->engines_mutex);
> > +
> > +             free_engines(engines);
> > +     }
> > +
> >       if (pc->single_timeline) {
> >               ret = drm_syncobj_create(&ctx->syncobj,
> >                                        DRM_SYNCOBJ_CREATE_SIGNALED,
> > @@ -916,12 +1387,12 @@ void i915_gem_init__contexts(struct drm_i915_private *i915)
> >       init_contexts(&i915->gem.contexts);
> >  }
> >
> > -static int gem_context_register(struct i915_gem_context *ctx,
> > -                             struct drm_i915_file_private *fpriv,
> > -                             u32 *id)
> > +static void gem_context_register(struct i915_gem_context *ctx,
> > +                              struct drm_i915_file_private *fpriv,
> > +                              u32 id)
> >  {
> >       struct drm_i915_private *i915 = ctx->i915;
> > -     int ret;
> > +     void *old;
> >
> >       ctx->file_priv = fpriv;
> >
> > @@ -930,19 +1401,12 @@ static int gem_context_register(struct i915_gem_context *ctx,
> >                current->comm, pid_nr(ctx->pid));
> >
> >       /* And finally expose ourselves to userspace via the idr */
> > -     ret = xa_alloc(&fpriv->context_xa, id, ctx, xa_limit_32b, GFP_KERNEL);
> > -     if (ret)
> > -             goto err_pid;
> > +     old = xa_store(&fpriv->context_xa, id, ctx, GFP_KERNEL);
> > +     GEM_BUG_ON(old);
> >
> >       spin_lock(&i915->gem.contexts.lock);
> >       list_add_tail(&ctx->link, &i915->gem.contexts.list);
> >       spin_unlock(&i915->gem.contexts.lock);
> > -
> > -     return 0;
> > -
> > -err_pid:
> > -     put_pid(fetch_and_zero(&ctx->pid));
> > -     return ret;
> >  }
> >
> >  int i915_gem_context_open(struct drm_i915_private *i915,
> > @@ -952,9 +1416,12 @@ int i915_gem_context_open(struct drm_i915_private *i915,
> >       struct i915_gem_proto_context *pc;
> >       struct i915_gem_context *ctx;
> >       int err;
> > -     u32 id;
> >
> > -     xa_init_flags(&file_priv->context_xa, XA_FLAGS_ALLOC);
> > +     mutex_init(&file_priv->proto_context_lock);
> > +     xa_init_flags(&file_priv->proto_context_xa, XA_FLAGS_ALLOC);
> > +
> > +     /* 0 reserved for the default context */
> > +     xa_init_flags(&file_priv->context_xa, XA_FLAGS_ALLOC1);
> >
> >       /* 0 reserved for invalid/unassigned ppgtt */
> >       xa_init_flags(&file_priv->vm_xa, XA_FLAGS_ALLOC1);
> > @@ -972,28 +1439,31 @@ int i915_gem_context_open(struct drm_i915_private *i915,
> >               goto err;
> >       }
> >
> > -     err = gem_context_register(ctx, file_priv, &id);
> > -     if (err < 0)
> > -             goto err_ctx;
> > +     gem_context_register(ctx, file_priv, 0);
> >
> > -     GEM_BUG_ON(id);
> >       return 0;
> >
> > -err_ctx:
> > -     context_close(ctx);
> >  err:
> >       xa_destroy(&file_priv->vm_xa);
> >       xa_destroy(&file_priv->context_xa);
> > +     xa_destroy(&file_priv->proto_context_xa);
> > +     mutex_destroy(&file_priv->proto_context_lock);
> >       return err;
> >  }
> >
> >  void i915_gem_context_close(struct drm_file *file)
> >  {
> >       struct drm_i915_file_private *file_priv = file->driver_priv;
> > +     struct i915_gem_proto_context *pc;
> >       struct i915_address_space *vm;
> >       struct i915_gem_context *ctx;
> >       unsigned long idx;
> >
> > +     xa_for_each(&file_priv->proto_context_xa, idx, pc)
> > +             proto_context_close(pc);
> > +     xa_destroy(&file_priv->proto_context_xa);
> > +     mutex_destroy(&file_priv->proto_context_lock);
> > +
> >       xa_for_each(&file_priv->context_xa, idx, ctx)
> >               context_close(ctx);
> >       xa_destroy(&file_priv->context_xa);
> > @@ -1918,7 +2388,7 @@ static int ctx_setparam(struct drm_i915_file_private *fpriv,
> >  }
> >
> >  struct create_ext {
> > -     struct i915_gem_context *ctx;
> > +     struct i915_gem_proto_context *pc;
> >       struct drm_i915_file_private *fpriv;
> >  };
> >
> > @@ -1933,7 +2403,7 @@ static int create_setparam(struct i915_user_extension __user *ext, void *data)
> >       if (local.param.ctx_id)
> >               return -EINVAL;
> >
> > -     return ctx_setparam(arg->fpriv, arg->ctx, &local.param);
> > +     return set_proto_ctx_param(arg->fpriv, arg->pc, &local.param);
> >  }
> >
> >  static int invalid_ext(struct i915_user_extension __user *ext, void *data)
> > @@ -1951,12 +2421,71 @@ static bool client_is_banned(struct drm_i915_file_private *file_priv)
> >       return atomic_read(&file_priv->ban_score) >= I915_CLIENT_SCORE_BANNED;
> >  }
> >
> > +static inline struct i915_gem_context *
> > +__context_lookup(struct drm_i915_file_private *file_priv, u32 id)
> > +{
> > +     struct i915_gem_context *ctx;
> > +
> > +     rcu_read_lock();
> > +     ctx = xa_load(&file_priv->context_xa, id);
> > +     if (ctx && !kref_get_unless_zero(&ctx->ref))
> > +             ctx = NULL;
> > +     rcu_read_unlock();
> > +
> > +     return ctx;
> > +}
> > +
> > +struct i915_gem_context *
> > +lazy_create_context_locked(struct drm_i915_file_private *file_priv,
> > +                        struct i915_gem_proto_context *pc, u32 id)
> > +{
> > +     struct i915_gem_context *ctx;
> > +     void *old;
>
> assert_lock_held is alwasy nice in all _locked functions. It entirely
> compiles out without CONFIG_PROVE_LOCKING enabled.

Done.

> > +
> > +     ctx = i915_gem_create_context(file_priv->dev_priv, pc);
>
> I think we need a prep patch which changes the calling convetion of this
> and anything it calls to only return a NULL pointer. Then
> i915_gem_context_lookup below can return the ERR_PTR(-ENOMEM) below for
> that case, and we know that we're never returning a wrong error pointer.
>
> > +     if (IS_ERR(ctx))
> > +             return ctx;
> > +
> > +     gem_context_register(ctx, file_priv, id);
> > +
> > +     old = xa_erase(&file_priv->proto_context_xa, id);
> > +     GEM_BUG_ON(old != pc);
> > +     proto_context_close(pc);
> > +
> > +     /* One for the xarray and one for the caller */
> > +     return i915_gem_context_get(ctx);
> > +}
> > +
> > +struct i915_gem_context *
> > +i915_gem_context_lookup(struct drm_i915_file_private *file_priv, u32 id)
> > +{
> > +     struct i915_gem_proto_context *pc;
> > +     struct i915_gem_context *ctx;
> > +
> > +     ctx = __context_lookup(file_priv, id);
> > +     if (ctx)
> > +             return ctx;
> > +
> > +     mutex_lock(&file_priv->proto_context_lock);
> > +     /* Try one more time under the lock */
> > +     ctx = __context_lookup(file_priv, id);
> > +     if (!ctx) {
> > +             pc = xa_load(&file_priv->proto_context_xa, id);
> > +             if (!pc)
> > +                     ctx = ERR_PTR(-ENOENT);
> > +             else
> > +                     ctx = lazy_create_context_locked(file_priv, pc, id);
> > +     }
> > +     mutex_unlock(&file_priv->proto_context_lock);
> > +
> > +     return ctx;
> > +}
> > +
> >  int i915_gem_context_create_ioctl(struct drm_device *dev, void *data,
> >                                 struct drm_file *file)
> >  {
> >       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;
> > @@ -1979,14 +2508,9 @@ int i915_gem_context_create_ioctl(struct drm_device *dev, void *data,
> >               return -EIO;
> >       }
> >
> > -     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);
> > +     ext_data.pc = proto_context_create(i915, args->flags);
> > +     if (IS_ERR(ext_data.pc))
> > +             return PTR_ERR(ext_data.pc);
> >
> >       if (args->flags & I915_CONTEXT_CREATE_FLAGS_USE_EXTENSIONS) {
> >               ret = i915_user_extensions(u64_to_user_ptr(args->extensions),
> > @@ -1994,20 +2518,20 @@ int i915_gem_context_create_ioctl(struct drm_device *dev, void *data,
> >                                          ARRAY_SIZE(create_extensions),
> >                                          &ext_data);
> >               if (ret)
> > -                     goto err_ctx;
> > +                     goto err_pc;
> >       }
> >
> > -     ret = gem_context_register(ext_data.ctx, ext_data.fpriv, &id);
> > +     ret = proto_context_register(ext_data.fpriv, ext_data.pc, &id);
> >       if (ret < 0)
> > -             goto err_ctx;
> > +             goto err_pc;
> >
> >       args->ctx_id = id;
> >       drm_dbg(&i915->drm, "HW context %d created\n", args->ctx_id);
> >
> >       return 0;
> >
> > -err_ctx:
> > -     context_close(ext_data.ctx);
> > +err_pc:
> > +     proto_context_close(ext_data.pc);
> >       return ret;
> >  }
> >
> > @@ -2016,6 +2540,7 @@ int i915_gem_context_destroy_ioctl(struct drm_device *dev, void *data,
> >  {
> >       struct drm_i915_gem_context_destroy *args = data;
> >       struct drm_i915_file_private *file_priv = file->driver_priv;
> > +     struct i915_gem_proto_context *pc;
> >       struct i915_gem_context *ctx;
> >
> >       if (args->pad != 0)
> > @@ -2024,11 +2549,21 @@ int i915_gem_context_destroy_ioctl(struct drm_device *dev, void *data,
> >       if (!args->ctx_id)
> >               return -ENOENT;
> >
> > +     mutex_lock(&file_priv->proto_context_lock);
> >       ctx = xa_erase(&file_priv->context_xa, args->ctx_id);
> > -     if (!ctx)
> > +     pc = xa_erase(&file_priv->proto_context_xa, args->ctx_id);
> > +     mutex_unlock(&file_priv->proto_context_lock);
> > +
> > +     if (!ctx && !pc)
> >               return -ENOENT;
> > +     GEM_WARN_ON(ctx && pc);
> > +
> > +     if (pc)
> > +             proto_context_close(pc);
> > +
> > +     if (ctx)
> > +             context_close(ctx);
> >
> > -     context_close(ctx);
> >       return 0;
> >  }
> >
> > @@ -2161,16 +2696,48 @@ int i915_gem_context_setparam_ioctl(struct drm_device *dev, void *data,
> >  {
> >       struct drm_i915_file_private *file_priv = file->driver_priv;
> >       struct drm_i915_gem_context_param *args = data;
> > +     struct i915_gem_proto_context *pc;
> >       struct i915_gem_context *ctx;
> > -     int ret;
> > +     int ret = 0;
> >
> > -     ctx = i915_gem_context_lookup(file_priv, args->ctx_id);
> > -     if (IS_ERR(ctx))
> > -             return PTR_ERR(ctx);
> > +     ctx = __context_lookup(file_priv, args->ctx_id);
> > +     if (ctx)
> > +             goto set_ctx_param;
> >
> > -     ret = ctx_setparam(file_priv, ctx, args);
> > +     mutex_lock(&file_priv->proto_context_lock);
> > +     ctx = __context_lookup(file_priv, args->ctx_id);
> > +     if (ctx)
> > +             goto unlock;
> > +
> > +     pc = xa_load(&file_priv->proto_context_xa, args->ctx_id);
> > +     if (!pc) {
> > +             ret = -ENOENT;
> > +             goto unlock;
> > +     }
> > +
> > +     ret = set_proto_ctx_param(file_priv, pc, args);
>
> I think we should have a FIXME here of not allowing this on some future
> platforms because just use CTX_CREATE_EXT.

Done.

> > +     if (ret == -ENOTSUPP) {
> > +             /* Some params, specifically SSEU, can only be set on fully
>
> I think this needs a FIXME: that this only holds during the conversion?
> Otherwise we kinda have a bit a problem me thinks ...

I'm not sure what you mean by that.

> > +              * created contexts.
> > +              */
> > +             ret = 0;
> > +             ctx = lazy_create_context_locked(file_priv, pc, args->ctx_id);
> > +             if (IS_ERR(ctx)) {
> > +                     ret = PTR_ERR(ctx);
> > +                     ctx = NULL;
> > +             }
> > +     }
> > +
> > +unlock:
> > +     mutex_unlock(&file_priv->proto_context_lock);
> > +
> > +set_ctx_param:
> > +     if (!ret && ctx)
> > +             ret = ctx_setparam(file_priv, ctx, args);
> > +
> > +     if (ctx)
> > +             i915_gem_context_put(ctx);
> >
> > -     i915_gem_context_put(ctx);
> >       return ret;
> >  }
> >
> > diff --git a/drivers/gpu/drm/i915/gem/i915_gem_context.h b/drivers/gpu/drm/i915/gem/i915_gem_context.h
> > index b5c908f3f4f22..20411db84914a 100644
> > --- a/drivers/gpu/drm/i915/gem/i915_gem_context.h
> > +++ b/drivers/gpu/drm/i915/gem/i915_gem_context.h
> > @@ -133,6 +133,9 @@ int i915_gem_context_setparam_ioctl(struct drm_device *dev, void *data,
> >  int i915_gem_context_reset_stats_ioctl(struct drm_device *dev, void *data,
> >                                      struct drm_file *file);
> >
> > +struct i915_gem_context *
> > +i915_gem_context_lookup(struct drm_i915_file_private *file_priv, u32 id);
> > +
> >  static inline struct i915_gem_context *
> >  i915_gem_context_get(struct i915_gem_context *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 a42c429f94577..067ea3030ac91 100644
> > --- a/drivers/gpu/drm/i915/gem/i915_gem_context_types.h
> > +++ b/drivers/gpu/drm/i915/gem/i915_gem_context_types.h
> > @@ -46,6 +46,26 @@ struct i915_gem_engines_iter {
> >       const struct i915_gem_engines *engines;
> >  };
> >
> > +enum i915_gem_engine_type {
> > +     I915_GEM_ENGINE_TYPE_INVALID = 0,
> > +     I915_GEM_ENGINE_TYPE_PHYSICAL,
> > +     I915_GEM_ENGINE_TYPE_BALANCED,
> > +};
> > +
>
> Some kerneldoc missing?

Yup.  Fixed.

> > +struct i915_gem_proto_engine {
> > +     /** @type: Type of this engine */
> > +     enum i915_gem_engine_type type;
> > +
> > +     /** @num_siblings: Engine, for physical */
> > +     struct intel_engine_cs *engine;
> > +
> > +     /** @num_siblings: Number of balanced siblings */
> > +     unsigned int num_siblings;
> > +
> > +     /** @num_siblings: Balanced siblings */
> > +     struct intel_engine_cs **siblings;
>
> I guess you're stuffing both balanced and siblings into one?

Nope.  Thanks to the patch to disable balance+bonded, we just throw
the bonding info away. :-D

> > +};
> > +
> >  /**
> >   * struct i915_gem_proto_context - prototype context
> >   *
> > @@ -64,6 +84,12 @@ struct i915_gem_proto_context {
> >       /** @sched: See i915_gem_context::sched */
> >       struct i915_sched_attr sched;
> >
> > +     /** @num_user_engines: Number of user-specified engines or -1 */
> > +     int num_user_engines;
> > +
> > +     /** @num_user_engines: User-specified engines */
> > +     struct i915_gem_proto_engine *user_engines;
> > +
> >       bool single_timeline;
> >  };
> >
> > diff --git a/drivers/gpu/drm/i915/gem/selftests/mock_context.c b/drivers/gpu/drm/i915/gem/selftests/mock_context.c
> > index e0f512ef7f3c6..32cf2103828f9 100644
> > --- a/drivers/gpu/drm/i915/gem/selftests/mock_context.c
> > +++ b/drivers/gpu/drm/i915/gem/selftests/mock_context.c
> > @@ -80,6 +80,7 @@ void mock_init_contexts(struct drm_i915_private *i915)
> >  struct i915_gem_context *
> >  live_context(struct drm_i915_private *i915, struct file *file)
> >  {
> > +     struct drm_i915_file_private *fpriv = to_drm_file(file)->driver_priv;
> >       struct i915_gem_proto_context *pc;
> >       struct i915_gem_context *ctx;
> >       int err;
> > @@ -96,10 +97,12 @@ live_context(struct drm_i915_private *i915, struct file *file)
> >
> >       i915_gem_context_set_no_error_capture(ctx);
> >
> > -     err = gem_context_register(ctx, to_drm_file(file)->driver_priv, &id);
> > +     err = xa_alloc(&fpriv->context_xa, &id, NULL, xa_limit_32b, GFP_KERNEL);
> >       if (err < 0)
> >               goto err_ctx;
> >
> > +     gem_context_register(ctx, fpriv, id);
> > +
> >       return ctx;
> >
> >  err_ctx:
> > diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> > index 004ed0e59c999..365c042529d72 100644
> > --- a/drivers/gpu/drm/i915/i915_drv.h
> > +++ b/drivers/gpu/drm/i915/i915_drv.h
> > @@ -200,6 +200,9 @@ struct drm_i915_file_private {
> >               struct rcu_head rcu;
> >       };
> >
> > +     struct mutex proto_context_lock;
> > +     struct xarray proto_context_xa;
>
> Kerneldoc here please. Ideally also for the context_xa below (but maybe
> that's for later).
>
> Also please add a hint to the proto context struct that it's all fully
> protected by proto_context_lock above and is never visible outside of
> that.

Both done.

> > +
> >       struct xarray context_xa;
> >       struct xarray vm_xa;
> >
> > @@ -1840,20 +1843,6 @@ struct drm_gem_object *i915_gem_prime_import(struct drm_device *dev,
> >
> >  struct dma_buf *i915_gem_prime_export(struct drm_gem_object *gem_obj, int flags);
> >
> > -static inline struct i915_gem_context *
> > -i915_gem_context_lookup(struct drm_i915_file_private *file_priv, u32 id)
> > -{
> > -     struct i915_gem_context *ctx;
> > -
> > -     rcu_read_lock();
> > -     ctx = xa_load(&file_priv->context_xa, id);
> > -     if (ctx && !kref_get_unless_zero(&ctx->ref))
> > -             ctx = NULL;
> > -     rcu_read_unlock();
> > -
> > -     return ctx ? ctx : ERR_PTR(-ENOENT);
> > -}
> > -
> >  /* i915_gem_evict.c */
> >  int __must_check i915_gem_evict_something(struct i915_address_space *vm,
> >                                         u64 min_size, u64 alignment,
>
> I think I'll check details when I'm not getting distracted by the
> vm/engines validation code that I think shouldn't be here :-)

No worries.  I should be sending out a new version of the series
shortly that's hopefully easier to read.

--Jason
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