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drm/i915: Allow userspace to clone contexts on creation

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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.

The ideal here is that we don't expose control over anything more than
can be obtained via CONTEXT_PARAM. That is userspace retains explicit
control over all features, and this api is just convenience.

For example, you could replace

	struct context_param p = { .param = CONTEXT_PARAM_VM };

	param.ctx_id = old_id;
	gem_context_get_param(&p.param);

	new_id = gem_context_create();

	param.ctx_id = new_id;
	gem_context_set_param(&p.param);

	gem_vm_destroy(param.value); /* drop the ref to VM_ID handle */

with

	struct create_ext_param p = {
	  { .name = CONTEXT_CREATE_CLONE },
	  .clone_id = old_id,
	  .flags = CLONE_FLAGS_VM
	}
	new_id = gem_context_create_ext(&p);

and not have to worry about stray namespace pollution etc.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190521211134.16117-5-chris@chris-wilson.co.uk
This commit is contained in:
Chris Wilson
2019-05-21 22:11:29 +01:00
parent 8319f44c05
commit b81dde7194
2 changed files with 221 additions and 0 deletions
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15
include/uapi/drm/i915_drm.h
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@@ -1624,6 +1624,21 @@ struct drm_i915_gem_context_create_ext_setparam {
struct drm_i915_gem_context_param param;
};
struct drm_i915_gem_context_create_ext_clone {
#define I915_CONTEXT_CREATE_EXT_CLONE 1
struct i915_user_extension base;
__u32 clone_id;
__u32 flags;
#define I915_CONTEXT_CLONE_ENGINES (1u << 0)
#define I915_CONTEXT_CLONE_FLAGS (1u << 1)
#define I915_CONTEXT_CLONE_SCHEDATTR (1u << 2)
#define I915_CONTEXT_CLONE_SSEU (1u << 3)
#define I915_CONTEXT_CLONE_TIMELINE (1u << 4)
#define I915_CONTEXT_CLONE_VM (1u << 5)
#define I915_CONTEXT_CLONE_UNKNOWN -(I915_CONTEXT_CLONE_VM << 1)
__u64 rsvd;
};
struct drm_i915_gem_context_destroy {
__u32 ctx_id;
__u32 pad;