Re: [PATCH v2 06/11] drm/i915: Move pinning of dev_priv->kernel_context into its creator

Tvrtko Ursulin
2016-05-23T12:09:09Z

On 23/05/16 12:34, Chris Wilson wrote:
> Rather than have every context ask "am I owned by the kernel? pin!",
> move that logic into the creator of the kernel context, in order to
> improve code comprehension.
>
> v2: Throw away the user_handle on failure to allocate the ppgtt.
>
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
> Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
> ---
> drivers/gpu/drm/i915/i915_gem_context.c | 53 +++++++++++++++------------------
> 1 file changed, 24 insertions(+), 29 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_gem_context.c b/drivers/gpu/drm/i915/i915_gem_context.c
> index a4c6377eea32..474174c20be2 100644
> --- a/drivers/gpu/drm/i915/i915_gem_context.c
> +++ b/drivers/gpu/drm/i915/i915_gem_context.c
> @@ -303,9 +303,7 @@ static struct i915_gem_context *
> i915_gem_create_context(struct drm_device *dev,
> struct drm_i915_file_private *file_priv)
> {
> - const bool is_global_default_ctx = file_priv == NULL;
> struct i915_gem_context *ctx;
> - int ret = 0;
>
> BUG_ON(!mutex_is_locked(&dev->struct_mutex));
>
> @@ -313,30 +311,15 @@ i915_gem_create_context(struct drm_device *dev,
> if (IS_ERR(ctx))
> return ctx;
>
> - if (is_global_default_ctx && ctx->legacy_hw_ctx.rcs_state) {
> - /* We may need to do things with the shrinker which
> - * require us to immediately switch back to the default
> - * context. This can cause a problem as pinning the
> - * default context also requires GTT space which may not
> - * be available. To avoid this we always pin the default
> - * context.
> - */
> - ret = i915_gem_obj_ggtt_pin(ctx->legacy_hw_ctx.rcs_state,
> - get_context_alignment(to_i915(dev)), 0);
> - if (ret) {
> - DRM_DEBUG_DRIVER("Couldn't pin %d\n", ret);
> - goto err_destroy;
> - }
> - }
> -
> if (USES_FULL_PPGTT(dev)) {
> struct i915_hw_ppgtt *ppgtt = i915_ppgtt_create(dev, file_priv);
>
> - if (IS_ERR_OR_NULL(ppgtt)) {
> + if (IS_ERR(ppgtt)) {
> DRM_DEBUG_DRIVER("PPGTT setup failed (%ld)\n",
> PTR_ERR(ppgtt));
> - ret = PTR_ERR(ppgtt);
> - goto err_unpin;
> + idr_remove(&file_priv->context_idr, ctx->user_handle);
> + i915_gem_context_put(ctx);
> + return ERR_CAST(ppgtt);
> }
>
> ctx->ppgtt = ppgtt;
> @@ -345,14 +328,6 @@ i915_gem_create_context(struct drm_device *dev,
> trace_i915_context_create(ctx);
>
> return ctx;
> -
> -err_unpin:
> - if (is_global_default_ctx && ctx->legacy_hw_ctx.rcs_state)
> - i915_gem_object_ggtt_unpin(ctx->legacy_hw_ctx.rcs_state);
> -err_destroy:
> - idr_remove(&file_priv->context_idr, ctx->user_handle);
> - i915_gem_context_put(ctx);
> - return ERR_PTR(ret);
> }
>
> static void i915_gem_context_unpin(struct i915_gem_context *ctx,
> @@ -426,6 +401,26 @@ int i915_gem_context_init(struct drm_device *dev)
> return PTR_ERR(ctx);
> }
>
> + if (ctx->legacy_hw_ctx.rcs_state) {
> + int ret;
> +
> + /* We may need to do things with the shrinker which
> + * require us to immediately switch back to the default
> + * context. This can cause a problem as pinning the
> + * default context also requires GTT space which may not
> + * be available. To avoid this we always pin the default
> + * context.
> + */
> + ret = i915_gem_obj_ggtt_pin(ctx->legacy_hw_ctx.rcs_state,
> + get_context_alignment(dev_priv), 0);
> + if (ret) {
> + DRM_ERROR("Failed to pinned default global context (error %d)\n",
> + ret);

idr_remove here as well? Maybe we should split out the idr context API
from the GEM context to make it explicit - create context, export it to
userspace and back?

> + i915_gem_context_put(ctx);
> + return ret;
> + }
> + }
> +
> dev_priv->kernel_context = ctx;
>
> DRM_DEBUG_DRIVER("%s context support initialized\n",
>

Regards,

Tvrtko