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

[Niranjana Vishwanathapura <niranjana.vishwanathapura@intel.com>]

On Wed, Nov 09, 2022 at 05:52:54PM +0000, Matthew Auld wrote:
>On Mon, 7 Nov 2022 at 08:53, Niranjana Vishwanathapura
><niranjana.vishwanathapura@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@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.

Ah, got missed out in this patch. It should be called from vm_unbind
path. Will fix it.

Thanks,
Niranjana

>
>> +{
>> +       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
>>