Re: [Intel-gfx] [RFC 34/60] drm/i915: introduce kernel blitter_context
+Chris Wilson
On Mon, Aug 3, 2020 at 12:59 PM Lucas De Marchi
wrote:
>
> On Fri, Jul 10, 2020 at 5:00 AM Matthew Auld wrote:
> >
> > We may be without a context to perform various internal blitter
> > operations, for example when performing object migration. Piggybacking
> > off the kernel_context is probably a bad idea, since it has other uses.
> >
> > Signed-off-by: Matthew Auld
> > Cc: Joonas Lahtinen
> > Cc: Abdiel Janulgue
> > ---
> > drivers/gpu/drm/i915/gt/intel_engine_cs.c| 30 +---
> > drivers/gpu/drm/i915/gt/intel_engine_types.h | 1 +
> > 2 files changed, 27 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/gt/intel_engine_cs.c
> > b/drivers/gpu/drm/i915/gt/intel_engine_cs.c
> > index dd1a42c4d344..1df94e82550f 100644
> > --- a/drivers/gpu/drm/i915/gt/intel_engine_cs.c
> > +++ b/drivers/gpu/drm/i915/gt/intel_engine_cs.c
> > @@ -792,6 +792,7 @@ create_kernel_context(struct intel_engine_cs *engine)
> > int err;
> >
> > ce = intel_context_create(engine);
> > +
> > if (IS_ERR(ce))
> > return ce;
> >
> > @@ -845,16 +846,32 @@ static int engine_init_common(struct intel_engine_cs
> > *engine)
> > return PTR_ERR(ce);
> >
> > ret = measure_breadcrumb_dw(ce);
> > - if (ret < 0)
> > - goto err_context;
> > + if (ret < 0) {
> > + intel_context_put(ce);
>
> I think it's easier to follow the code if the error handling is in one
> place. Since you have to put the context.
> And since create_kernel_context() pins it, don't we have to
> intel_context_unpin() like we are doing
> in intel_engine_cleanup_common()? Which would also mean to probably
> factor out a `destroy_kernel_context()`
> to always do it, and call from here and from intel_engine_cleanup_common().
We actually had a destroy_kernel_context() and the unpin, but that got dropped
by e6ba76480299 ("drm/i915: Remove i915->kernel_context") .
Wouldn't we hit a GEM_BUG_ON() in the destroy function if we don't unpin it ?
Lucas De Marchi
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Re: [Intel-gfx] [RFC 34/60] drm/i915: introduce kernel blitter_context
On Fri, Jul 10, 2020 at 5:00 AM Matthew Auld wrote:
>
> We may be without a context to perform various internal blitter
> operations, for example when performing object migration. Piggybacking
> off the kernel_context is probably a bad idea, since it has other uses.
>
> Signed-off-by: Matthew Auld
> Cc: Joonas Lahtinen
> Cc: Abdiel Janulgue
> ---
> drivers/gpu/drm/i915/gt/intel_engine_cs.c| 30 +---
> drivers/gpu/drm/i915/gt/intel_engine_types.h | 1 +
> 2 files changed, 27 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/gt/intel_engine_cs.c
> b/drivers/gpu/drm/i915/gt/intel_engine_cs.c
> index dd1a42c4d344..1df94e82550f 100644
> --- a/drivers/gpu/drm/i915/gt/intel_engine_cs.c
> +++ b/drivers/gpu/drm/i915/gt/intel_engine_cs.c
> @@ -792,6 +792,7 @@ create_kernel_context(struct intel_engine_cs *engine)
> int err;
>
> ce = intel_context_create(engine);
> +
> if (IS_ERR(ce))
> return ce;
>
> @@ -845,16 +846,32 @@ static int engine_init_common(struct intel_engine_cs
> *engine)
> return PTR_ERR(ce);
>
> ret = measure_breadcrumb_dw(ce);
> - if (ret < 0)
> - goto err_context;
> + if (ret < 0) {
> + intel_context_put(ce);
I think it's easier to follow the code if the error handling is in one
place. Since you have to put the context.
And since create_kernel_context() pins it, don't we have to
intel_context_unpin() like we are doing
in intel_engine_cleanup_common()? Which would also mean to probably
factor out a `destroy_kernel_context()`
to always do it, and call from here and from intel_engine_cleanup_common().
Lucas De Marchi
> + return ret;
> + }
>
> engine->emit_fini_breadcrumb_dw = ret;
> engine->kernel_context = ce;
>
> + /*
> +* The blitter context is used to quickly memset or migrate objects
> +* in local memory, so it has to always be available.
> +*/
> + if (engine->class == COPY_ENGINE_CLASS) {
> + ce = create_kernel_context(engine);
> + if (IS_ERR(ce)) {
> + ret = PTR_ERR(ce);
> + goto err_kernel_context;
> + }
> +
> + engine->blitter_context = ce;
> + }
> +
> return 0;
>
> -err_context:
> - intel_context_put(ce);
> +err_kernel_context:
> + intel_context_put(engine->kernel_context);
> return ret;
> }
>
> @@ -910,6 +927,11 @@ void intel_engine_cleanup_common(struct intel_engine_cs
> *engine)
> if (engine->default_state)
> fput(engine->default_state);
>
> + if (engine->blitter_context) {
> + intel_context_unpin(engine->blitter_context);
> + intel_context_put(engine->blitter_context);
> + }
> +
> if (engine->kernel_context) {
> intel_context_unpin(engine->kernel_context);
> intel_context_put(engine->kernel_context);
> diff --git a/drivers/gpu/drm/i915/gt/intel_engine_types.h
> b/drivers/gpu/drm/i915/gt/intel_engine_types.h
> index 490af81bd6f3..3b2d9ed7670f 100644
> --- a/drivers/gpu/drm/i915/gt/intel_engine_types.h
> +++ b/drivers/gpu/drm/i915/gt/intel_engine_types.h
> @@ -342,6 +342,7 @@ struct intel_engine_cs {
> struct llist_head barrier_tasks;
>
> struct intel_context *kernel_context; /* pinned */
> + struct intel_context *blitter_context; /* pinned; exists for BCS only
> */
>
> intel_engine_mask_t saturated; /* submitting semaphores too late? */
>
> --
> 2.26.2
>
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[Intel-gfx] [RFC 34/60] drm/i915: introduce kernel blitter_context
We may be without a context to perform various internal blitter
operations, for example when performing object migration. Piggybacking
off the kernel_context is probably a bad idea, since it has other uses.
Signed-off-by: Matthew Auld
Cc: Joonas Lahtinen
Cc: Abdiel Janulgue
---
drivers/gpu/drm/i915/gt/intel_engine_cs.c| 30 +---
drivers/gpu/drm/i915/gt/intel_engine_types.h | 1 +
2 files changed, 27 insertions(+), 4 deletions(-)
diff --git a/drivers/gpu/drm/i915/gt/intel_engine_cs.c
b/drivers/gpu/drm/i915/gt/intel_engine_cs.c
index dd1a42c4d344..1df94e82550f 100644
--- a/drivers/gpu/drm/i915/gt/intel_engine_cs.c
+++ b/drivers/gpu/drm/i915/gt/intel_engine_cs.c
@@ -792,6 +792,7 @@ create_kernel_context(struct intel_engine_cs *engine)
int err;
ce = intel_context_create(engine);
+
if (IS_ERR(ce))
return ce;
@@ -845,16 +846,32 @@ static int engine_init_common(struct intel_engine_cs
*engine)
return PTR_ERR(ce);
ret = measure_breadcrumb_dw(ce);
- if (ret < 0)
- goto err_context;
+ if (ret < 0) {
+ intel_context_put(ce);
+ return ret;
+ }
engine->emit_fini_breadcrumb_dw = ret;
engine->kernel_context = ce;
+ /*
+* The blitter context is used to quickly memset or migrate objects
+* in local memory, so it has to always be available.
+*/
+ if (engine->class == COPY_ENGINE_CLASS) {
+ ce = create_kernel_context(engine);
+ if (IS_ERR(ce)) {
+ ret = PTR_ERR(ce);
+ goto err_kernel_context;
+ }
+
+ engine->blitter_context = ce;
+ }
+
return 0;
-err_context:
- intel_context_put(ce);
+err_kernel_context:
+ intel_context_put(engine->kernel_context);
return ret;
}
@@ -910,6 +927,11 @@ void intel_engine_cleanup_common(struct intel_engine_cs
*engine)
if (engine->default_state)
fput(engine->default_state);
+ if (engine->blitter_context) {
+ intel_context_unpin(engine->blitter_context);
+ intel_context_put(engine->blitter_context);
+ }
+
if (engine->kernel_context) {
intel_context_unpin(engine->kernel_context);
intel_context_put(engine->kernel_context);
diff --git a/drivers/gpu/drm/i915/gt/intel_engine_types.h
b/drivers/gpu/drm/i915/gt/intel_engine_types.h
index 490af81bd6f3..3b2d9ed7670f 100644
--- a/drivers/gpu/drm/i915/gt/intel_engine_types.h
+++ b/drivers/gpu/drm/i915/gt/intel_engine_types.h
@@ -342,6 +342,7 @@ struct intel_engine_cs {
struct llist_head barrier_tasks;
struct intel_context *kernel_context; /* pinned */
+ struct intel_context *blitter_context; /* pinned; exists for BCS only */
intel_engine_mask_t saturated; /* submitting semaphores too late? */
--
2.26.2
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