Re: [PATCH] drm/xe: Return -ENOBUFS if a kmalloc fails which is tied to an array of binds

["Ghimiray, Himal Prasad" <himal.prasad.ghimiray@intel.com>]

On 19-07-2024 22:53, Matthew Brost wrote:
> The size of an array of binds is directly tied to several kmalloc in the
> KMD, thus making these kmalloc more likely to fail. Return -ENOBUFS in
> the case of these failures.
> 
> The expected UMD behavior upon returning -ENOBUFS is to split an array
> of binds into a series of single binds.

Would it be appropriate to have some doc/guidelines in the form of 
drm_err or kernel doc regarding expected behavior from UMD if the ioctl 
returns a -ENOBUFS error ?

> 
> Cc: Paulo Zanoni <paulo.r.zanoni@intel.com>
> Signed-off-by: Matthew Brost <matthew.brost@intel.com>
> ---
>   drivers/gpu/drm/xe/xe_vm.c | 12 ++++++------
>   1 file changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/gpu/drm/xe/xe_vm.c b/drivers/gpu/drm/xe/xe_vm.c
> index 3fde2c8292ad..b715883f40d8 100644
> --- a/drivers/gpu/drm/xe/xe_vm.c
> +++ b/drivers/gpu/drm/xe/xe_vm.c
> @@ -718,7 +718,7 @@ int xe_vm_userptr_check_repin(struct xe_vm *vm)
>   		list_empty_careful(&vm->userptr.invalidated)) ? 0 : -EAGAIN;
>   }
>   
> -static int xe_vma_ops_alloc(struct xe_vma_ops *vops)
> +static int xe_vma_ops_alloc(struct xe_vma_ops *vops, bool array_of_binds)
>   {
>   	int i;
>   
> @@ -731,7 +731,7 @@ static int xe_vma_ops_alloc(struct xe_vma_ops *vops)
>   				      sizeof(*vops->pt_update_ops[i].ops),
>   				      GFP_KERNEL);
>   		if (!vops->pt_update_ops[i].ops)
> -			return -ENOMEM;
> +			return array_of_binds ? -ENOBUFS : -ENOMEM;
>   	}
>   
>   	return 0;
> @@ -824,7 +824,7 @@ int xe_vm_rebind(struct xe_vm *vm, bool rebind_worker)
>   			goto free_ops;
>   	}
>   
> -	err = xe_vma_ops_alloc(&vops);
> +	err = xe_vma_ops_alloc(&vops, false);
>   	if (err)
>   		goto free_ops;
>   
> @@ -871,7 +871,7 @@ struct dma_fence *xe_vma_rebind(struct xe_vm *vm, struct xe_vma *vma, u8 tile_ma
>   	if (err)
>   		return ERR_PTR(err);
>   
> -	err = xe_vma_ops_alloc(&vops);
> +	err = xe_vma_ops_alloc(&vops, false);
>   	if (err) {
>   		fence = ERR_PTR(err);
>   		goto free_ops;
> @@ -2765,7 +2765,7 @@ static int vm_bind_ioctl_check_args(struct xe_device *xe,
>   					   sizeof(struct drm_xe_vm_bind_op),
>   					   GFP_KERNEL | __GFP_ACCOUNT);
>   		if (!*bind_ops)
> -			return -ENOMEM;
> +			return args->num_binds > 1 ? -ENOBUFS : -ENOMEM;
>   
>   		err = __copy_from_user(*bind_ops, bind_user,
>   				       sizeof(struct drm_xe_vm_bind_op) *
> @@ -3104,7 +3104,7 @@ int xe_vm_bind_ioctl(struct drm_device *dev, void *data, struct drm_file *file)
>   		goto unwind_ops;
>   	}
>   
> -	err = xe_vma_ops_alloc(&vops);
> +	err = xe_vma_ops_alloc(&vops, args->num_binds > 1);
>   	if (err)
>   		goto unwind_ops;
>