A usecase arose out of handling context recovery in mesa, whereby they
wish to recreate a context with fresh logical state but preserving all
other details of the original. Currently, they create a new context and
iterate over which bits they want to copy across, but it would much more
convenient if they were able to just pass in a target context to clone
during creation. This essentially extends the setparam during creation
to pull the details from a target context instead of the user supplied
parameters.

Signed-off-by: Chris Wilson <ch...@chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/i915_gem_context.c | 71 +++++++++++++++++++++++++
 include/uapi/drm/i915_drm.h             | 14 +++++
 2 files changed, 85 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_gem_context.c 
b/drivers/gpu/drm/i915/i915_gem_context.c
index d8e2228636ba..48fb2ffb5f8c 100644
--- a/drivers/gpu/drm/i915/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/i915_gem_context.c
@@ -1456,8 +1456,79 @@ static int create_setparam(struct i915_user_extension 
__user *ext, void *data)
        return ctx_setparam(data, &local.setparam);
 }
 
+static void clone_sseu(struct i915_gem_context *dst,
+                      struct i915_gem_context *src)
+{
+       const struct intel_sseu default_sseu =
+               intel_device_default_sseu(dst->i915);
+       struct intel_engine_cs *engine;
+       enum intel_engine_id id;
+
+       for_each_engine(engine, dst->i915, id) {
+               struct intel_context *ce;
+               struct intel_sseu sseu;
+
+               ce = to_intel_context(src, engine);
+               if (!ce)
+                       continue;
+
+               sseu = ce->sseu;
+               if (!memcmp(&sseu, &default_sseu, sizeof(sseu)))
+                       continue;
+
+               ce = to_intel_context(dst, engine);
+               ce->sseu = sseu;
+       }
+}
+
+static int create_clone(struct i915_user_extension __user *ext, void *data)
+{
+       struct drm_i915_gem_context_create_ext_clone local;
+       struct i915_gem_context *dst = data;
+       struct i915_gem_context *src;
+
+       if (copy_from_user(&local, ext, sizeof(local)))
+               return -EFAULT;
+
+       if (local.flags & I915_CONTEXT_CLONE_UNKNOWN)
+               return -EINVAL;
+
+       if (local.rsvd)
+               return -EINVAL;
+
+       rcu_read_lock();
+       src = __i915_gem_context_lookup_rcu(dst->file_priv, local.clone);
+       rcu_read_unlock();
+       if (!src)
+               return -ENOENT;
+
+       if (local.flags & I915_CONTEXT_CLONE_FLAGS)
+               dst->user_flags = src->user_flags;
+
+       if (local.flags & I915_CONTEXT_CLONE_SCHED)
+               dst->sched = src->sched;
+
+       if (local.flags & I915_CONTEXT_CLONE_SSEU)
+               clone_sseu(dst, src);
+
+       if (local.flags & I915_CONTEXT_CLONE_TIMELINE && src->timeline) {
+               if (dst->timeline)
+                       i915_timeline_put(dst->timeline);
+               dst->timeline = i915_timeline_get(src->timeline);
+       }
+
+       if (local.flags & I915_CONTEXT_CLONE_VM && src->ppgtt) {
+               if (dst->ppgtt)
+                       i915_ppgtt_put(dst->ppgtt);
+               dst->ppgtt = i915_ppgtt_get(src->ppgtt);
+       }
+
+       return 0;
+}
+
 static const i915_user_extension_fn create_extensions[] = {
        [I915_CONTEXT_CREATE_EXT_SETPARAM] = create_setparam,
+       [I915_CONTEXT_CREATE_EXT_CLONE] = create_clone,
 };
 
 static bool client_is_banned(struct drm_i915_file_private *file_priv)
diff --git a/include/uapi/drm/i915_drm.h b/include/uapi/drm/i915_drm.h
index 451d2f36830b..60cbb2e4f140 100644
--- a/include/uapi/drm/i915_drm.h
+++ b/include/uapi/drm/i915_drm.h
@@ -1577,6 +1577,20 @@ struct drm_i915_gem_context_create_ext_setparam {
        struct drm_i915_gem_context_param setparam;
 };
 
+struct drm_i915_gem_context_create_ext_clone {
+#define I915_CONTEXT_CREATE_EXT_CLONE 1
+       struct i915_user_extension base;
+       __u32 clone;
+       __u32 flags;
+#define I915_CONTEXT_CLONE_FLAGS       (1u << 0)
+#define I915_CONTEXT_CLONE_SCHED       (1u << 1)
+#define I915_CONTEXT_CLONE_SSEU                (1u << 2)
+#define I915_CONTEXT_CLONE_TIMELINE    (1u << 3)
+#define I915_CONTEXT_CLONE_VM          (1u << 4)
+#define I915_CONTEXT_CLONE_UNKNOWN -(I915_CONTEXT_CLONE_VM << 1)
+       __u64 rsvd;
+};
+
 struct drm_i915_gem_context_destroy {
        __u32 ctx_id;
        __u32 pad;
-- 
2.20.1

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