Re: [PATCH] drm/xe: Use vmalloc for array of bind allocation in bind IOCTL

["Thomas Hellström" <thomas.hellstrom@linux.intel.com>]

Hi, Matt
On Fri, 2024-02-23 at 11:37 -0800, Matthew Brost wrote:
> Use vmalloc in effort to allow a user pass in a large number of binds
> in
> an IOCTL (mesa use case). Also use array allocations rather open
> coding
> the size calculation.

I still think allowing a large number of binds like this is a bit
dangerous, because to avoid out-of-memory DOSes we will need to
restrict the number of binds in some way. And if the UMDs can't
gracefully handle the OOMS and retry with a smaller number of binds
they will break. And we're not allowed to break the.....

Did we end up keeping a max number of binds that we guarantee for
forseeable future?

/Thomas


> 
> Fixes: dd08ebf6c352 ("drm/xe: Introduce a new DRM driver for Intel
> GPUs")
> Signed-off-by: Matthew Brost <matthew.brost@intel.com>
> ---
>  drivers/gpu/drm/xe/xe_vm.c | 23 ++++++++++++-----------
>  1 file changed, 12 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/gpu/drm/xe/xe_vm.c b/drivers/gpu/drm/xe/xe_vm.c
> index e3bde897f6e8..45a12207ebf5 100644
> --- a/drivers/gpu/drm/xe/xe_vm.c
> +++ b/drivers/gpu/drm/xe/xe_vm.c
> @@ -2778,8 +2778,9 @@ static int vm_bind_ioctl_check_args(struct
> xe_device *xe,
>  		u64 __user *bind_user =
>  			u64_to_user_ptr(args->vector_of_binds);
>  
> -		*bind_ops = kmalloc(sizeof(struct drm_xe_vm_bind_op)
> *
> -				    args->num_binds, GFP_KERNEL);
> +		*bind_ops = kvmalloc_array(args->num_binds,
> +					   sizeof(struct
> drm_xe_vm_bind_op),
> +					   GFP_KERNEL);
>  		if (!*bind_ops)
>  			return -ENOMEM;
>  
> @@ -2869,7 +2870,7 @@ static int vm_bind_ioctl_check_args(struct
> xe_device *xe,
>  
>  free_bind_ops:
>  	if (args->num_binds > 1)
> -		kfree(*bind_ops);
> +		kvfree(*bind_ops);
>  	return err;
>  }
>  
> @@ -2957,13 +2958,13 @@ int xe_vm_bind_ioctl(struct drm_device *dev,
> void *data, struct drm_file *file)
>  	}
>  
>  	if (args->num_binds) {
> -		bos = kcalloc(args->num_binds, sizeof(*bos),
> GFP_KERNEL);
> +		bos = kvcalloc(args->num_binds, sizeof(*bos),
> GFP_KERNEL);
>  		if (!bos) {
>  			err = -ENOMEM;
>  			goto release_vm_lock;
>  		}
>  
> -		ops = kcalloc(args->num_binds, sizeof(*ops),
> GFP_KERNEL);
> +		ops = kvcalloc(args->num_binds, sizeof(*ops),
> GFP_KERNEL);
>  		if (!ops) {
>  			err = -ENOMEM;
>  			goto release_vm_lock;
> @@ -3104,10 +3105,10 @@ int xe_vm_bind_ioctl(struct drm_device *dev,
> void *data, struct drm_file *file)
>  	for (i = 0; bos && i < args->num_binds; ++i)
>  		xe_bo_put(bos[i]);
>  
> -	kfree(bos);
> -	kfree(ops);
> +	kvfree(bos);
> +	kvfree(ops);
>  	if (args->num_binds > 1)
> -		kfree(bind_ops);
> +		kvfree(bind_ops);
>  
>  	return err;
>  
> @@ -3131,10 +3132,10 @@ int xe_vm_bind_ioctl(struct drm_device *dev,
> void *data, struct drm_file *file)
>  	if (q)
>  		xe_exec_queue_put(q);
>  free_objs:
> -	kfree(bos);
> -	kfree(ops);
> +	kvfree(bos);
> +	kvfree(ops);
>  	if (args->num_binds > 1)
> -		kfree(bind_ops);
> +		kvfree(bind_ops);
>  	return err;
>  }
>