[PATCH] drm/i915: Only mark the ctx as initialised after a SET_CONTEXT operation

[PATCH] drm/i915: Only mark the ctx as initialised after a SET_CONTEXT operation

[Chris Wilson]

Fallout from

commit 46470fc932ac8a0e8317a220b3f4ea4ed903338e
Author: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Date:   Wed May 21 19:01:06 2014 +0300

    drm/i915: Add null state batch to active list

undid the earlier fix of only marking the ctx as initialised after it is
saved by the hardware during a SET_CONTEXT operation.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Damien Lespiau <damien.lespiau@intel.com>
Cc: Mika Kuoppala <mika.kuoppala@intel.com>
Cc: Ben Widawsky <ben@bwidawsk.net>
---
 drivers/gpu/drm/i915/i915_gem_context.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem_context.c b/drivers/gpu/drm/i915/i915_gem_context.c
index 5a71ef1975b3..34a0b49e6add 100644
--- a/drivers/gpu/drm/i915/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/i915_gem_context.c
@@ -641,6 +641,7 @@ static int do_switch(struct intel_engine_cs *ring,
 	struct intel_context *from = ring->last_context;
 	struct i915_hw_ppgtt *ppgtt = ctx_to_ppgtt(to);
 	u32 hw_flags = 0;
+	bool uninitialized = false;
 	int ret, i;
 
 	if (from != NULL && ring == &dev_priv->ring[RCS]) {
@@ -739,18 +740,19 @@ static int do_switch(struct intel_engine_cs *ring,
 		i915_gem_context_unreference(from);
 	}
 
+	uninitialized = !to->is_initialized && from == NULL;
+	to->is_initialized = true;
+
 done:
 	i915_gem_context_reference(to);
 	ring->last_context = to;
 
-	if (ring->id == RCS && !to->is_initialized && from == NULL) {
+	if (uninitialized) {
 		ret = i915_gem_render_state_init(ring);
 		if (ret)
 			DRM_ERROR("init render state: %d\n", ret);
 	}
 
-	to->is_initialized = true;
-
 	return 0;
 
 unpin_out:
-- 
2.0.0.rc4

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Re: [PATCH] drm/i915: Only mark the ctx as initialised after a SET_CONTEXT operation

[Ben Widawsky]

On Fri, May 30, 2014 at 02:16:30PM +0100, Chris Wilson wrote:
> Fallout from
> 
> commit 46470fc932ac8a0e8317a220b3f4ea4ed903338e
> Author: Mika Kuoppala <mika.kuoppala@linux.intel.com>
> Date:   Wed May 21 19:01:06 2014 +0300
> 
>     drm/i915: Add null state batch to active list
> 
> undid the earlier fix of only marking the ctx as initialised after it is
> saved by the hardware during a SET_CONTEXT operation.
> 
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> Cc: Damien Lespiau <damien.lespiau@intel.com>
> Cc: Mika Kuoppala <mika.kuoppala@intel.com>
> Cc: Ben Widawsky <ben@bwidawsk.net>
> ---
>  drivers/gpu/drm/i915/i915_gem_context.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_gem_context.c b/drivers/gpu/drm/i915/i915_gem_context.c
> index 5a71ef1975b3..34a0b49e6add 100644
> --- a/drivers/gpu/drm/i915/i915_gem_context.c
> +++ b/drivers/gpu/drm/i915/i915_gem_context.c
> @@ -641,6 +641,7 @@ static int do_switch(struct intel_engine_cs *ring,
>  	struct intel_context *from = ring->last_context;
>  	struct i915_hw_ppgtt *ppgtt = ctx_to_ppgtt(to);
>  	u32 hw_flags = 0;
> +	bool uninitialized = false;
>  	int ret, i;
>  
>  	if (from != NULL && ring == &dev_priv->ring[RCS]) {
> @@ -739,18 +740,19 @@ static int do_switch(struct intel_engine_cs *ring,
>  		i915_gem_context_unreference(from);
>  	}
>  
> +	uninitialized = !to->is_initialized && from == NULL;
> +	to->is_initialized = true;

Aren't you missing some error paths if you do this?  I think we need to
set the state after we've successfully emitted the MI_SET_CONTEXT
command (though really, until we move the ringbuffer tail, it's all
lies, on that note, I'm scared to look at if reset dtrt).

> +
>  done:
>  	i915_gem_context_reference(to);
>  	ring->last_context = to;
>  
> -	if (ring->id == RCS && !to->is_initialized && from == NULL) {
> +	if (uninitialized) {
>  		ret = i915_gem_render_state_init(ring);
>  		if (ret)
>  			DRM_ERROR("init render state: %d\n", ret);
>  	}
>  
> -	to->is_initialized = true;
> -
>  	return 0;
>  
>  unpin_out:

I just realized the from == NULL check is something which seems fragile
to me given how much churn we might see with init/reset paths. It'd
probably be good to eventually switch to some global state in dev_priv
which we can track across init/reset/fini

Otherwise it looks correct to me.

-- 
Ben Widawsky, Intel Open Source Technology Center
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Re: [PATCH] drm/i915: Only mark the ctx as initialised after a SET_CONTEXT operation

[Chris Wilson]

On Fri, May 30, 2014 at 10:44:53AM -0700, Ben Widawsky wrote:
> On Fri, May 30, 2014 at 02:16:30PM +0100, Chris Wilson wrote:
> > Fallout from
> > 
> > commit 46470fc932ac8a0e8317a220b3f4ea4ed903338e
> > Author: Mika Kuoppala <mika.kuoppala@linux.intel.com>
> > Date:   Wed May 21 19:01:06 2014 +0300
> > 
> >     drm/i915: Add null state batch to active list
> > 
> > undid the earlier fix of only marking the ctx as initialised after it is
> > saved by the hardware during a SET_CONTEXT operation.
> > 
> > Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> > Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > Cc: Damien Lespiau <damien.lespiau@intel.com>
> > Cc: Mika Kuoppala <mika.kuoppala@intel.com>
> > Cc: Ben Widawsky <ben@bwidawsk.net>
> > ---
> >  drivers/gpu/drm/i915/i915_gem_context.c | 8 +++++---
> >  1 file changed, 5 insertions(+), 3 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/i915_gem_context.c b/drivers/gpu/drm/i915/i915_gem_context.c
> > index 5a71ef1975b3..34a0b49e6add 100644
> > --- a/drivers/gpu/drm/i915/i915_gem_context.c
> > +++ b/drivers/gpu/drm/i915/i915_gem_context.c
> > @@ -641,6 +641,7 @@ static int do_switch(struct intel_engine_cs *ring,
> >  	struct intel_context *from = ring->last_context;
> >  	struct i915_hw_ppgtt *ppgtt = ctx_to_ppgtt(to);
> >  	u32 hw_flags = 0;
> > +	bool uninitialized = false;
> >  	int ret, i;
> >  
> >  	if (from != NULL && ring == &dev_priv->ring[RCS]) {
> > @@ -739,18 +740,19 @@ static int do_switch(struct intel_engine_cs *ring,
> >  		i915_gem_context_unreference(from);
> >  	}
> >  
> > +	uninitialized = !to->is_initialized && from == NULL;
> > +	to->is_initialized = true;
> 
> Aren't you missing some error paths if you do this?  I think we need to
> set the state after we've successfully emitted the MI_SET_CONTEXT
> command (though really, until we move the ringbuffer tail, it's all
> lies, on that note, I'm scared to look at if reset dtrt).

I also think that until we successfully emit the MI_SET_CONTEXT and
allow the execbuffer to proceed, we can continue to treat the context as
garbage and force-inhibit on the next attempt to run the execbuffer.
 
> > +
> >  done:
> >  	i915_gem_context_reference(to);
> >  	ring->last_context = to;
> >  
> > -	if (ring->id == RCS && !to->is_initialized && from == NULL) {
> > +	if (uninitialized) {
> >  		ret = i915_gem_render_state_init(ring);
> >  		if (ret)
> >  			DRM_ERROR("init render state: %d\n", ret);
> >  	}
> >  
> > -	to->is_initialized = true;
> > -
> >  	return 0;
> >  
> >  unpin_out:
> 
> I just realized the from == NULL check is something which seems fragile
> to me given how much churn we might see with init/reset paths. It'd
> probably be good to eventually switch to some global state in dev_priv
> which we can track across init/reset/fini

It's as fragile as the bug we are papering over. Presumably we do need
to apply fresh paper after a GPU reset, but it is hard to tell without
knowing the bug.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre

Re: [PATCH] drm/i915: Only mark the ctx as initialised after a SET_CONTEXT operation

[Chris Wilson]

On Fri, May 30, 2014 at 02:16:30PM +0100, Chris Wilson wrote:
> Fallout from
> 
> commit 46470fc932ac8a0e8317a220b3f4ea4ed903338e
> Author: Mika Kuoppala <mika.kuoppala@linux.intel.com>
> Date:   Wed May 21 19:01:06 2014 +0300
> 
>     drm/i915: Add null state batch to active list
> 
> undid the earlier fix of only marking the ctx as initialised after it is
> saved by the hardware during a SET_CONTEXT operation.
> 
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> Cc: Damien Lespiau <damien.lespiau@intel.com>
> Cc: Mika Kuoppala <mika.kuoppala@intel.com>
> Cc: Ben Widawsky <ben@bwidawsk.net>

Ping. Ben's comments do not impact upon the urgent need for this fix.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre

Re: [PATCH] drm/i915: Only mark the ctx as initialised after a SET_CONTEXT operation

[Daniel Vetter]

On Tue, Jun 10, 2014 at 11:34:34AM +0100, Chris Wilson wrote:
> On Fri, May 30, 2014 at 02:16:30PM +0100, Chris Wilson wrote:
> > Fallout from
> > 
> > commit 46470fc932ac8a0e8317a220b3f4ea4ed903338e
> > Author: Mika Kuoppala <mika.kuoppala@linux.intel.com>
> > Date:   Wed May 21 19:01:06 2014 +0300
> > 
> >     drm/i915: Add null state batch to active list
> > 
> > undid the earlier fix of only marking the ctx as initialised after it is
> > saved by the hardware during a SET_CONTEXT operation.
> > 
> > Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> > Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > Cc: Damien Lespiau <damien.lespiau@intel.com>
> > Cc: Mika Kuoppala <mika.kuoppala@intel.com>
> > Cc: Ben Widawsky <ben@bwidawsk.net>
> 
> Ping. Ben's comments do not impact upon the urgent need for this fix.

Ok, this code is extremely convoluted. ctx->last_ring is terrible, and we
should make a clear disdinction of which ctx->foo fields are for the
logical context and which for the per-engine stuff. Will be much more
important for execlists so that we properly fan out the state.

I'm ranting here a bit since it took me a while to realize that
->is_initialized is _only_ for the RCS stuff. I guess we should have
ctx->obj[ring] and ctx->is_initialized[ring] or even better, a substruct
i915_hw_context with an array.

</rant>

With that out of the way, this is Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>

Thanks, Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch

Re: [PATCH] drm/i915: Only mark the ctx as initialised after a SET_CONTEXT operation

[Jani Nikula]

On Fri, 30 May 2014, Chris Wilson <chris@chris-wilson.co.uk> wrote:
> Fallout from
>
> commit 46470fc932ac8a0e8317a220b3f4ea4ed903338e
> Author: Mika Kuoppala <mika.kuoppala@linux.intel.com>
> Date:   Wed May 21 19:01:06 2014 +0300
>
>     drm/i915: Add null state batch to active list
>
> undid the earlier fix of only marking the ctx as initialised after it is
> saved by the hardware during a SET_CONTEXT operation.
>
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> Cc: Damien Lespiau <damien.lespiau@intel.com>
> Cc: Mika Kuoppala <mika.kuoppala@intel.com>
> Cc: Ben Widawsky <ben@bwidawsk.net>

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=79108

> ---
>  drivers/gpu/drm/i915/i915_gem_context.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_gem_context.c b/drivers/gpu/drm/i915/i915_gem_context.c
> index 5a71ef1975b3..34a0b49e6add 100644
> --- a/drivers/gpu/drm/i915/i915_gem_context.c
> +++ b/drivers/gpu/drm/i915/i915_gem_context.c
> @@ -641,6 +641,7 @@ static int do_switch(struct intel_engine_cs *ring,
>  	struct intel_context *from = ring->last_context;
>  	struct i915_hw_ppgtt *ppgtt = ctx_to_ppgtt(to);
>  	u32 hw_flags = 0;
> +	bool uninitialized = false;
>  	int ret, i;
>  
>  	if (from != NULL && ring == &dev_priv->ring[RCS]) {
> @@ -739,18 +740,19 @@ static int do_switch(struct intel_engine_cs *ring,
>  		i915_gem_context_unreference(from);
>  	}
>  
> +	uninitialized = !to->is_initialized && from == NULL;
> +	to->is_initialized = true;
> +
>  done:
>  	i915_gem_context_reference(to);
>  	ring->last_context = to;
>  
> -	if (ring->id == RCS && !to->is_initialized && from == NULL) {
> +	if (uninitialized) {
>  		ret = i915_gem_render_state_init(ring);
>  		if (ret)
>  			DRM_ERROR("init render state: %d\n", ret);
>  	}
>  
> -	to->is_initialized = true;
> -
>  	return 0;
>  
>  unpin_out:
> -- 
> 2.0.0.rc4
>
> _______________________________________________
> Intel-gfx mailing list
> Intel-gfx@lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/intel-gfx

-- 
Jani Nikula, Intel Open Source Technology Center
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Re: [PATCH] drm/i915: Only mark the ctx as initialised after a SET_CONTEXT operation

[Ben Widawsky]

On Mon, Jun 23, 2014 at 12:55:47PM +0300, Jani Nikula wrote:
> On Fri, 30 May 2014, Chris Wilson <chris@chris-wilson.co.uk> wrote:
> > Fallout from
> >
> > commit 46470fc932ac8a0e8317a220b3f4ea4ed903338e
> > Author: Mika Kuoppala <mika.kuoppala@linux.intel.com>
> > Date:   Wed May 21 19:01:06 2014 +0300
> >
> >     drm/i915: Add null state batch to active list
> >
> > undid the earlier fix of only marking the ctx as initialised after it is
> > saved by the hardware during a SET_CONTEXT operation.
> >
> > Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> > Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > Cc: Damien Lespiau <damien.lespiau@intel.com>
> > Cc: Mika Kuoppala <mika.kuoppala@intel.com>
> > Cc: Ben Widawsky <ben@bwidawsk.net>
> 
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=79108
> 

Daniel put his IRC r-b on this on IIRC.

[snip]

-- 
Ben Widawsky, Intel Open Source Technology Center
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Re: [PATCH] drm/i915: Only mark the ctx as initialised after a SET_CONTEXT operation

[Jani Nikula]

On Mon, 23 Jun 2014, Ben Widawsky <ben@bwidawsk.net> wrote:
> On Mon, Jun 23, 2014 at 12:55:47PM +0300, Jani Nikula wrote:
>> On Fri, 30 May 2014, Chris Wilson <chris@chris-wilson.co.uk> wrote:
>> > Fallout from
>> >
>> > commit 46470fc932ac8a0e8317a220b3f4ea4ed903338e
>> > Author: Mika Kuoppala <mika.kuoppala@linux.intel.com>
>> > Date:   Wed May 21 19:01:06 2014 +0300
>> >
>> >     drm/i915: Add null state batch to active list
>> >
>> > undid the earlier fix of only marking the ctx as initialised after it is
>> > saved by the hardware during a SET_CONTEXT operation.
>> >
>> > Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
>> > Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
>> > Cc: Damien Lespiau <damien.lespiau@intel.com>
>> > Cc: Mika Kuoppala <mika.kuoppala@intel.com>
>> > Cc: Ben Widawsky <ben@bwidawsk.net>
>> 
>> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=79108
>> 
>
> Daniel put his IRC r-b on this on IIRC.

Pushed to -fixes, thanks for the patch and review.

BR,
Jani.


>
> [snip]
>
> -- 
> Ben Widawsky, Intel Open Source Technology Center

-- 
Jani Nikula, Intel Open Source Technology Center
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