Re: [Intel-gfx] [PATCH] drm/i915: Reserve enough fence slot for i915_vma_unbind_async

[Das, Nirmoy]

On 1/5/2023 10:56 AM, Matthew Auld wrote:

On Fri, 23 Dec 2022 at 09:20, Nirmoy Das  wrote:

A nested dma_resv_reserve_fences(1) will not reserve slot from the
2nd call onwards and folowing dma_resv_add_fence() might hit the
"BUG_ON(fobj->num_fences >= fobj->max_fences)" check.

I915 hit above nested dma_resv case in ttm_bo_handle_move_mem() with
async unbind:

dma_resv_reserve_fences() from --> ttm_bo_handle_move_mem()
 dma_resv_reserve_fences() from --> i915_vma_unbind_async()
 dma_resv_add_fence() from --> i915_vma_unbind_async()
dma_resv_add_fence() from -->ttm_bo_move_accel_cleanup()

Resolve this by adding an extra fence in i915_vma_unbind_async().

Suggested-by: Thomas Hellström 
Signed-off-by: Nirmoy Das 

Reviewed-by: Matthew Auld 

Does this need a fixes tag?

Fixes: 2f6b90da9192 ("drm/i915: Use vma resources for async unbinding")
Cc:  # v5.18+

I can add when pushing.



Yes, please add that.


Thanks,

Nirmoy




---
  drivers/gpu/drm/i915/i915_vma.c | 2 +-
  1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/i915_vma.c b/drivers/gpu/drm/i915/i915_vma.c
index 7d044888ac33..5ac4c1c2403c 100644
--- a/drivers/gpu/drm/i915/i915_vma.c
+++ b/drivers/gpu/drm/i915/i915_vma.c
@@ -2149,7 +2149,7 @@ int i915_vma_unbind_async(struct i915_vma *vma, bool 
trylock_vm)
 if (!obj->mm.rsgt)
 return -EBUSY;

-   err = dma_resv_reserve_fences(obj->base.resv, 1);
+   err = dma_resv_reserve_fences(obj->base.resv, 2);
 if (err)
 return -EBUSY;

--
2.38.0

Re: [Intel-gfx] [PATCH] drm/i915: Reserve enough fence slot for i915_vma_unbind_async

[Matthew Auld]

On Fri, 23 Dec 2022 at 09:20, Nirmoy Das  wrote:
>
> A nested dma_resv_reserve_fences(1) will not reserve slot from the
> 2nd call onwards and folowing dma_resv_add_fence() might hit the
> "BUG_ON(fobj->num_fences >= fobj->max_fences)" check.
>
> I915 hit above nested dma_resv case in ttm_bo_handle_move_mem() with
> async unbind:
>
> dma_resv_reserve_fences() from --> ttm_bo_handle_move_mem()
> dma_resv_reserve_fences() from --> i915_vma_unbind_async()
> dma_resv_add_fence() from --> i915_vma_unbind_async()
> dma_resv_add_fence() from -->ttm_bo_move_accel_cleanup()
>
> Resolve this by adding an extra fence in i915_vma_unbind_async().
>
> Suggested-by: Thomas Hellström 
> Signed-off-by: Nirmoy Das 
Reviewed-by: Matthew Auld 

Does this need a fixes tag?

Fixes: 2f6b90da9192 ("drm/i915: Use vma resources for async unbinding")
Cc:  # v5.18+

I can add when pushing.

> ---
>  drivers/gpu/drm/i915/i915_vma.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_vma.c b/drivers/gpu/drm/i915/i915_vma.c
> index 7d044888ac33..5ac4c1c2403c 100644
> --- a/drivers/gpu/drm/i915/i915_vma.c
> +++ b/drivers/gpu/drm/i915/i915_vma.c
> @@ -2149,7 +2149,7 @@ int i915_vma_unbind_async(struct i915_vma *vma, bool 
> trylock_vm)
> if (!obj->mm.rsgt)
> return -EBUSY;
>
> -   err = dma_resv_reserve_fences(obj->base.resv, 1);
> +   err = dma_resv_reserve_fences(obj->base.resv, 2);
> if (err)
> return -EBUSY;
>
> --
> 2.38.0
>

[Intel-gfx] [PATCH] drm/i915: Reserve enough fence slot for i915_vma_unbind_async

[Nirmoy Das]

A nested dma_resv_reserve_fences(1) will not reserve slot from the
2nd call onwards and folowing dma_resv_add_fence() might hit the
"BUG_ON(fobj->num_fences >= fobj->max_fences)" check.

I915 hit above nested dma_resv case in ttm_bo_handle_move_mem() with
async unbind:

dma_resv_reserve_fences() from --> ttm_bo_handle_move_mem()
dma_resv_reserve_fences() from --> i915_vma_unbind_async()
dma_resv_add_fence() from --> i915_vma_unbind_async()
dma_resv_add_fence() from -->ttm_bo_move_accel_cleanup()

Resolve this by adding an extra fence in i915_vma_unbind_async().

Suggested-by: Thomas Hellström 
Signed-off-by: Nirmoy Das 
---
 drivers/gpu/drm/i915/i915_vma.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/i915_vma.c b/drivers/gpu/drm/i915/i915_vma.c
index 7d044888ac33..5ac4c1c2403c 100644
--- a/drivers/gpu/drm/i915/i915_vma.c
+++ b/drivers/gpu/drm/i915/i915_vma.c
@@ -2149,7 +2149,7 @@ int i915_vma_unbind_async(struct i915_vma *vma, bool 
trylock_vm)
if (!obj->mm.rsgt)
return -EBUSY;
 
-   err = dma_resv_reserve_fences(obj->base.resv, 1);
+   err = dma_resv_reserve_fences(obj->base.resv, 2);
if (err)
return -EBUSY;
 
-- 
2.38.0