[PATCH v6 20/20] drm/i915/vm_bind: Async vm_unbind support

[Matthew Auld]

On Mon, 7 Nov 2022 at 08:53, Niranjana Vishwanathapura
<niranjana.vishwanathapura at intel.com> wrote:
>
> Asynchronously unbind the vma upon vm_unbind call.
> Fall back to synchronous unbind if backend doesn't support
> async unbind or if async unbind fails.
>
> No need for vm_unbind out fence support as i915 will internally
> handle all sequencing and user need not try to sequence any
> operation with the unbind completion.
>
> Signed-off-by: Niranjana Vishwanathapura <niranjana.vishwanathapura at intel.com>
> ---
>  drivers/gpu/drm/i915/i915_vma.c | 51 ++++++++++++++++++++++++++++++---
>  drivers/gpu/drm/i915/i915_vma.h |  1 +
>  2 files changed, 48 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_vma.c b/drivers/gpu/drm/i915/i915_vma.c
> index 08218e3a2f12..03c966fad87b 100644
> --- a/drivers/gpu/drm/i915/i915_vma.c
> +++ b/drivers/gpu/drm/i915/i915_vma.c
> @@ -42,6 +42,8 @@
>  #include "i915_vma.h"
>  #include "i915_vma_resource.h"
>
> +static struct dma_fence *__i915_vma_unbind_async(struct i915_vma *vma);
> +
>  static inline void assert_vma_held_evict(const struct i915_vma *vma)
>  {
>         /*
> @@ -1711,7 +1713,7 @@ void i915_vma_reopen(struct i915_vma *vma)
>         spin_unlock_irq(&gt->closed_lock);
>  }
>
> -static void force_unbind(struct i915_vma *vma)
> +static void force_unbind(struct i915_vma *vma, bool async)
>  {
>         if (!drm_mm_node_allocated(&vma->node))
>                 return;
> @@ -1725,7 +1727,21 @@ static void force_unbind(struct i915_vma *vma)
>                 i915_vma_set_purged(vma);
>
>         atomic_and(~I915_VMA_PIN_MASK, &vma->flags);
> -       WARN_ON(__i915_vma_unbind(vma));
> +       if (async) {
> +               struct dma_fence *fence;
> +
> +               fence = __i915_vma_unbind_async(vma);
> +               if (IS_ERR_OR_NULL(fence)) {
> +                       async = false;
> +               } else {
> +                       dma_resv_add_fence(vma->obj->base.resv, fence,
> +                                          DMA_RESV_USAGE_READ);
> +                       dma_fence_put(fence);
> +               }
> +       }
> +
> +       if (!async)
> +               WARN_ON(__i915_vma_unbind(vma));
>         GEM_BUG_ON(drm_mm_node_allocated(&vma->node));
>  }
>
> @@ -1785,7 +1801,7 @@ void i915_vma_destroy_locked(struct i915_vma *vma)
>  {
>         lockdep_assert_held(&vma->vm->mutex);
>
> -       force_unbind(vma);
> +       force_unbind(vma, false);
>         list_del_init(&vma->vm_link);
>         release_references(vma, vma->vm->gt, false);
>  }
> @@ -1796,7 +1812,34 @@ void i915_vma_destroy(struct i915_vma *vma)
>         bool vm_ddestroy;
>
>         mutex_lock(&vma->vm->mutex);
> -       force_unbind(vma);
> +       force_unbind(vma, false);
> +       list_del_init(&vma->vm_link);
> +       vm_ddestroy = vma->vm_ddestroy;
> +       vma->vm_ddestroy = false;
> +
> +       /* vma->vm may be freed when releasing vma->vm->mutex. */
> +       gt = vma->vm->gt;
> +       mutex_unlock(&vma->vm->mutex);
> +       release_references(vma, gt, vm_ddestroy);
> +}
> +
> +void i915_vma_destroy_async(struct i915_vma *vma)

Where are we calling this? I can't find it.

> +{
> +       bool vm_ddestroy, async = vma->obj->mm.rsgt;
> +       struct intel_gt *gt;
> +
> +       if (dma_resv_reserve_fences(vma->obj->base.resv, 1))
> +               async = false;
> +
> +       mutex_lock(&vma->vm->mutex);
> +       /*
> +        * Ensure any asynchronous binding is complete while using
> +        * async unbind as we will be releasing the vma here.
> +        */
> +       if (async && i915_active_wait(&vma->active))
> +               async = false;
> +
> +       force_unbind(vma, async);
>         list_del_init(&vma->vm_link);
>         vm_ddestroy = vma->vm_ddestroy;
>         vma->vm_ddestroy = false;
> diff --git a/drivers/gpu/drm/i915/i915_vma.h b/drivers/gpu/drm/i915/i915_vma.h
> index 737ef310d046..25f15965dab8 100644
> --- a/drivers/gpu/drm/i915/i915_vma.h
> +++ b/drivers/gpu/drm/i915/i915_vma.h
> @@ -272,6 +272,7 @@ void i915_vma_reopen(struct i915_vma *vma);
>
>  void i915_vma_destroy_locked(struct i915_vma *vma);
>  void i915_vma_destroy(struct i915_vma *vma);
> +void i915_vma_destroy_async(struct i915_vma *vma);
>
>  #define assert_vma_held(vma) dma_resv_assert_held((vma)->obj->base.resv)
>
> --
> 2.21.0.rc0.32.g243a4c7e27
>