drm/i915: Assign every HW context a unique ID

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.

v2: Reorder to make sure ctx->link is not left dangling if the
assignment of a hw_id fails (Mika).

v3: We have 21bits of context space, not 20.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1461833819-3991-17-git-send-email-chris@chris-wilson.co.uk

diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
index e1bc5ec..e35d0cc 100644 (file)
--- a/drivers/gpu/drm/i915/i915_debugfs.c
+++ b/drivers/gpu/drm/i915/i915_debugfs.c
@@ -2001,7 +2001,7 @@ 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 %u ", ctx->hw_id);
                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 831da9f..0f75752 100644 (file)
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -851,6 +851,9 @@ struct intel_context {
        struct i915_ctx_hang_stats hang_stats;
        struct i915_hw_ppgtt *ppgtt;
 
+       /* Unique identifier for this context, used by the hw for tracking */
+       unsigned hw_id;
+
        /* Legacy ring buffer submission */
        struct {
                struct drm_i915_gem_object *rcs_state;
@@ -1838,6 +1841,13 @@ struct drm_i915_private {
        DECLARE_HASHTABLE(mm_structs, 7);
        struct mutex mm_lock;
 
+       /* The hw wants to have a stable context identifier for the lifetime
+        * of the context (for OA, PASID, faults, etc). This is limited
+        * in execlists to 21 bits.
+        */
+       struct ida context_hw_ida;
+#define MAX_CONTEXT_HW_ID (1<<21) /* exclusive */
+
        /* Kernel Modesetting */
 
        struct drm_crtc *plane_to_crtc_mapping[I915_MAX_PIPES];

diff --git a/drivers/gpu/drm/i915/i915_gem_context.c b/drivers/gpu/drm/i915/i915_gem_context.c
index 2fea74b..25a9a14 100644 (file)
--- a/drivers/gpu/drm/i915/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/i915_gem_context.c
@@ -171,6 +171,8 @@ void i915_gem_context_free(struct kref *ctx_ref)
        if (ctx->legacy_hw_ctx.rcs_state)
                drm_gem_object_unreference(&ctx->legacy_hw_ctx.rcs_state->base);
        list_del(&ctx->link);
+
+       ida_simple_remove(&ctx->i915->context_hw_ida, ctx->hw_id);
        kfree(ctx);
 }
 
@@ -211,6 +213,28 @@ i915_gem_alloc_context_obj(struct drm_device *dev, size_t size)
        return obj;
 }
 
+static int assign_hw_id(struct drm_i915_private *dev_priv, unsigned *out)
+{
+       int ret;
+
+       ret = ida_simple_get(&dev_priv->context_hw_ida,
+                            0, MAX_CONTEXT_HW_ID, GFP_KERNEL);
+       if (ret < 0) {
+               /* Contexts are only released when no longer active.
+                * Flush any pending retires to hopefully release some
+                * stale contexts and try again.
+                */
+               i915_gem_retire_requests(dev_priv->dev);
+               ret = ida_simple_get(&dev_priv->context_hw_ida,
+                                    0, MAX_CONTEXT_HW_ID, GFP_KERNEL);
+               if (ret < 0)
+                       return ret;
+       }
+
+       *out = ret;
+       return 0;
+}
+
 static struct intel_context *
 __create_hw_context(struct drm_device *dev,
                    struct drm_i915_file_private *file_priv)
@@ -223,6 +247,12 @@ __create_hw_context(struct drm_device *dev,
        if (ctx == NULL)
                return ERR_PTR(-ENOMEM);
 
+       ret = assign_hw_id(dev_priv, &ctx->hw_id);
+       if (ret) {
+               kfree(ctx);
+               return ERR_PTR(ret);
+       }
+
        kref_init(&ctx->ref);
        list_add_tail(&ctx->link, &dev_priv->context_list);
        ctx->i915 = dev_priv;
@@ -366,6 +396,10 @@ int i915_gem_context_init(struct drm_device *dev)
                }
        }
 
+       /* Using the simple ida interface, the max is limited by sizeof(int) */
+       BUILD_BUG_ON(MAX_CONTEXT_HW_ID > INT_MAX);
+       ida_init(&dev_priv->context_hw_ida);
+
        if (i915.enable_execlists) {
                /* NB: intentionally left blank. We will allocate our own
                 * backing objects as we need them, thank you very much */
@@ -429,6 +463,8 @@ void i915_gem_context_fini(struct drm_device *dev)
 
        i915_gem_context_unreference(dctx);
        dev_priv->kernel_context = NULL;
+
+       ida_destroy(&dev_priv->context_hw_ida);
 }
 
 static int context_idr_cleanup(int id, void *p, void *data)