[Intel-gfx] [PATCH 16/29] drm/i915/gem: Add an intermediate proto_context struct
Jason Ekstrand
jason at jlekstrand.net
Wed Jun 2 21:24:42 UTC 2021
On Mon, May 31, 2021 at 3:47 AM Daniel Vetter <daniel at ffwll.ch> wrote:
>
> On Thu, May 27, 2021 at 11:26:37AM -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 engine set are in
>
> ^the
>
> At least my English parser jumped there a bit and got confused :-)
I believe what I wrote was correct but I'm happy to tweak it if it
helps others' parsers.
> > 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.
> >
> > Signed-off-by: Jason Ekstrand <jason at jlekstrand.net>
>
> I also looked at my review from the previous round and I think we have a
> few opens there that haven't been addressed here. Would be nice to check
> that out too and my reply there if you're disagreeing and want to paint
> the shed differently :-)
Ok, I'll try to dig it up. I miss GitLab and it's "resolve
discussion" button so much....
> I've found a few other things needing polish below on top of the earlier
> bits.
> -Daniel
>
> > ---
> > drivers/gpu/drm/i915/gem/i915_gem_context.c | 145 ++++++++++++++----
> > .../gpu/drm/i915/gem/i915_gem_context_types.h | 22 +++
> > .../gpu/drm/i915/gem/selftests/mock_context.c | 16 +-
> > 3 files changed, 153 insertions(+), 30 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/gem/i915_gem_context.c b/drivers/gpu/drm/i915/gem/i915_gem_context.c
> > index fc471243aa769..10bff488444b6 100644
> > --- a/drivers/gpu/drm/i915/gem/i915_gem_context.c
> > +++ b/drivers/gpu/drm/i915/gem/i915_gem_context.c
> > @@ -191,6 +191,97 @@ 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;
> > +
> > + __set_bit(UCONTEXT_PERSISTENCE, &pc->user_flags);
> > + } 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;
> > +
> > + __clear_bit(UCONTEXT_PERSISTENCE, &pc->user_flags);
> > + }
> > +
> > + 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);
> > +
> > + if (HAS_FULL_PPGTT(i915)) {
> > + struct i915_ppgtt *ppgtt;
> > +
> > + ppgtt = i915_ppgtt_create(&i915->gt);
> > + if (IS_ERR(ppgtt)) {
> > + drm_dbg(&i915->drm, "PPGTT setup failed (%ld)\n",
> > + PTR_ERR(ppgtt));
> > + err = ERR_CAST(ppgtt);
> > + goto proto_close;
> > + }
> > + pc->vm = &ppgtt->vm;
> > + }
> > +
> > + pc->user_flags = 0;
> > + __set_bit(UCONTEXT_BANNABLE, &pc->user_flags);
> > + __set_bit(UCONTEXT_RECOVERABLE, &pc->user_flags);
> > + proto_context_set_persistence(i915, pc, true);
>
> You've lost the error handling here.
No, I've not. This is where that helper is both wonderful and crazy
annoying. We could have a helper to check whether or not a particular
persistence setting is allowed. Instead (and this is what the old
code does too), it's initialized to false by kzalloc and then we try
to set it to true and ignore the failure. This ensures that,
regardless of which options are allowed, we'll end up with an allowed
one. Yeah, the more I type here the more I realize just how bad of an
idea that is. :-) If you'd like, we can refactor things to have a
validation function persistence_setting_valid() or maybe a pair
requires_persistence() and persistence_allowed(). I'm open to other
suggestions too.
> > + 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 +751,8 @@ 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 +765,7 @@ __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 +788,7 @@ __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;
> > @@ -786,38 +876,23 @@ 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)) {
> > - struct i915_ppgtt *ppgtt;
> > -
> > - ppgtt = i915_ppgtt_create(&i915->gt);
> > - if (IS_ERR(ppgtt)) {
> > - drm_dbg(&i915->drm, "PPGTT setup failed (%ld)\n",
> > - PTR_ERR(ppgtt));
> > - context_close(ctx);
> > - return ERR_CAST(ppgtt);
> > - }
> > -
> > + if (pc->vm) {
> > mutex_lock(&ctx->mutex);
> > - __assign_ppgtt(ctx, &ppgtt->vm);
> > + __assign_ppgtt(ctx, pc->vm);
> > mutex_unlock(&ctx->mutex);
> > -
> > - 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 +958,7 @@ 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 +968,14 @@ 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 +1967,7 @@ 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 +1990,12 @@ 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..0bf337b6d89ac 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
> > + * an i915_gem_context. This is used to gather parameters provided either
>
> a struct i915_gem_context
Done.
> With that you get an automatic neat hyperlink. See
>
> https://dri.freedesktop.org/docs/drm/doc-guide/kernel-doc.html#highlights-and-cross-references
>
> for what it all recognizes automatically.
>
> > + * 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 */
>
> Hyperlinks need &i915_gem_context.vm in kerneldoc. Same for the others
> below.
Fixed.
I'll try to dig through your previous one now. I thought I'd gotten
everything but clearly you found something I hadn't.
--Jason
> > + 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 at lists.freedesktop.org
> > https://lists.freedesktop.org/mailman/listinfo/intel-gfx
>
> --
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch
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