Re: [Intel-gfx] [PATCH v7 20/20] drm/i915/vm_bind: Async vm_unbind support

[Matthew Auld <matthew.auld@intel.com>]

On 15/11/2022 16:15, Niranjana Vishwanathapura wrote:
> On Tue, Nov 15, 2022 at 11:05:21AM +0000, Matthew Auld wrote:
>> On 13/11/2022 07:57, Niranjana Vishwanathapura 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.
>>>
>>> v2: use i915_vma_destroy_async in vm_unbind ioctl
>>>
>>> Signed-off-by: Niranjana Vishwanathapura 
>>> <niranjana.vishwanathapura@intel.com>
>>
>> This only does it for non-partial vma, right? Or was that changed 
>> somewhere?
>>
> 
> No, it applies to any vma (partial or non-partial).
> It was so from the beginning.

Doesn't __i915_vma_unbind_async() return an error when mm.pages != 
vma->pages? IIRC this was discussed before. Just trying to think about 
the consequences of this change.

> 
> Niranjana
> 
>> Reviewed-by: Matthew Auld <matthew.auld@intel.com>
>>
>>> ---
>>>  .../drm/i915/gem/i915_gem_vm_bind_object.c    |  2 +-
>>>  drivers/gpu/drm/i915/i915_vma.c               | 51 +++++++++++++++++--
>>>  drivers/gpu/drm/i915/i915_vma.h               |  1 +
>>>  include/uapi/drm/i915_drm.h                   |  3 +-
>>>  4 files changed, 51 insertions(+), 6 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_vm_bind_object.c 
>>> b/drivers/gpu/drm/i915/gem/i915_gem_vm_bind_object.c
>>> index d87d1210365b..36651b447966 100644
>>> --- a/drivers/gpu/drm/i915/gem/i915_gem_vm_bind_object.c
>>> +++ b/drivers/gpu/drm/i915/gem/i915_gem_vm_bind_object.c
>>> @@ -210,7 +210,7 @@ static int i915_gem_vm_unbind_vma(struct 
>>> i915_address_space *vm,
>>>       */
>>>      obj = vma->obj;
>>>      i915_gem_object_lock(obj, NULL);
>>> -    i915_vma_destroy(vma);
>>> +    i915_vma_destroy_async(vma);
>>>      i915_gem_object_unlock(obj);
>>>      i915_gem_object_put(obj);
>>> diff --git a/drivers/gpu/drm/i915/i915_vma.c 
>>> b/drivers/gpu/drm/i915/i915_vma.c
>>> index 7cf77c67d755..483d25f2425c 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)
>>>  {
>>>      /*
>>> @@ -1713,7 +1715,7 @@ 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;
>>> @@ -1727,7 +1729,21 @@ 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));
>>>  }
>>> @@ -1787,7 +1803,7 @@ 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);
>>>  }
>>> @@ -1798,7 +1814,34 @@ 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)
>>> +{
>>> +    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)
>>> diff --git a/include/uapi/drm/i915_drm.h b/include/uapi/drm/i915_drm.h
>>> index e5600f358a15..431d40bb1dee 100644
>>> --- a/include/uapi/drm/i915_drm.h
>>> +++ b/include/uapi/drm/i915_drm.h
>>> @@ -3969,7 +3969,8 @@ struct drm_i915_gem_vm_bind {
>>>   * any error.
>>>   *
>>>   * VM_BIND/UNBIND ioctl calls executed on different CPU threads 
>>> concurrently
>>> - * are not ordered.
>>> + * are not ordered. Furthermore, parts of the VM_UNBIND operation 
>>> can be done
>>> + * asynchronously.
>>>   */
>>>  struct drm_i915_gem_vm_unbind {
>>>      /** @vm_id: VM (address space) id to bind */