[Intel-gfx] [PATCH 1/9] drm/i915: Assign every HW context a unique ID

[Chris Wilson]

On Tue, Apr 19, 2016 at 09:57:14AM +0100, Tvrtko Ursulin wrote:
> 
> On 19/04/16 07:49, Chris Wilson wrote:
> >The hardware tracks contexts and expects all live contexts (those active
> >on the hardware) to have a unique identifier. This is used by the
> >hardware to assign pagefaults and the like to a particular context.
> >
> >Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> >---
> >  drivers/gpu/drm/i915/i915_debugfs.c     |  2 +-
> >  drivers/gpu/drm/i915/i915_drv.h         |  4 ++++
> >  drivers/gpu/drm/i915/i915_gem_context.c | 32 ++++++++++++++++++++++++++++++++
> >  3 files changed, 37 insertions(+), 1 deletion(-)
> >
> >diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
> >index ffc4734cb2dc..cacbe45b7938 100644
> >--- a/drivers/gpu/drm/i915/i915_debugfs.c
> >+++ b/drivers/gpu/drm/i915/i915_debugfs.c
> >@@ -2014,7 +2014,7 @@ static int i915_context_status(struct seq_file *m, void *unused)
> >  		    ctx->legacy_hw_ctx.rcs_state == NULL)
> >  			continue;
> >
> >-		seq_puts(m, "HW context ");
> >+		seq_printf(m, "HW context %d ", ctx->hw_id);
> 
> Should be %u.
> 
> >  		describe_ctx(m, ctx);
> >  		if (ctx == dev_priv->kernel_context)
> >  			seq_printf(m, "(kernel context) ");
> >diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> >index dc3bb5c10957..368fd7090189 100644
> >--- a/drivers/gpu/drm/i915/i915_drv.h
> >+++ b/drivers/gpu/drm/i915/i915_drv.h
> >@@ -851,6 +851,7 @@ struct intel_context {
> >  	struct i915_ctx_hang_stats hang_stats;
> >  	struct i915_hw_ppgtt *ppgtt;
> >
> >+	unsigned hw_id;
> >  	unsigned flags;
> >  #define CONTEXT_NO_ZEROMAP		(1<<0)
> >  #define CONTEXT_NO_ERROR_CAPTURE	(1<<1)
> >@@ -1810,6 +1811,9 @@ struct drm_i915_private {
> >  	DECLARE_HASHTABLE(mm_structs, 7);
> >  	struct mutex mm_lock;
> >
> >+	struct ida context_hw_ida;
> >+#define MAX_CONTEXT_HW_ID (1<<20)
> 
> BUILD_BUG_ON somewhere if someone in the future is tempted to
> increase this without realizing ids returned by ida_simple_get are
> limited to 0x80000000 ?

How do you fancy a BUILD_BUG_ON? (Just not seeing what I should assert.)
The max-value chosen here is lifted from the ctx-descriptor (as you
know). A comment is definitely in order to explain the limit.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre