[Intel-xe] [PATCH] drm/xe: Decrement fault mode counts in xe_vm_close_and_put

[Maarten Lankhorst]

Reviewed-by: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>

On 2023-03-21 17:08, Matthew Brost wrote:
> Rather waiting for the VM to be destroyed (all refs to VM go to zero),
> drop the fault mode counts when the VM is closed in xe_vm_close_and_put.
> This avoids a window where user space can create a faulting VM, close
> it, and a subsequent creation of a non-faulting VM fails.
>
> v2 (Lucas): Drop VLK reference in commit message
>
> Suggested-by: Niranjana Vishwanathapura <niranjana.vishwanathapura at intel.com>
> Signed-off-by: Matthew Brost <matthew.brost at intel.com>
> ---
>   drivers/gpu/drm/xe/xe_vm.c | 15 +++++++--------
>   1 file changed, 7 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/gpu/drm/xe/xe_vm.c b/drivers/gpu/drm/xe/xe_vm.c
> index 68ab51f84bed..ab036a51d17e 100644
> --- a/drivers/gpu/drm/xe/xe_vm.c
> +++ b/drivers/gpu/drm/xe/xe_vm.c
> @@ -1349,6 +1349,13 @@ void xe_vm_close_and_put(struct xe_vm *vm)
>   	XE_WARN_ON(!list_empty(&vm->extobj.list));
>   	up_write(&vm->lock);
>   
> +	mutex_lock(&xe->usm.lock);
> +	if (vm->flags & XE_VM_FLAG_FAULT_MODE)
> +		xe->usm.num_vm_in_fault_mode--;
> +	else if (!(vm->flags & XE_VM_FLAG_MIGRATION))
> +		xe->usm.num_vm_in_non_fault_mode--;
> +	mutex_unlock(&xe->usm.lock);
> +
>   	xe_vm_put(vm);
>   }
>   
> @@ -1393,18 +1400,10 @@ static void vm_destroy_work_func(struct work_struct *w)
>   
>   	drm_gpuva_manager_destroy(&vm->mgr);
>   
> -	mutex_lock(&xe->usm.lock);
> -	if (vm->flags & XE_VM_FLAG_FAULT_MODE)
> -		xe->usm.num_vm_in_fault_mode--;
> -	else if (!(vm->flags & XE_VM_FLAG_MIGRATION))
> -		xe->usm.num_vm_in_non_fault_mode--;
> -	mutex_unlock(&xe->usm.lock);
> -
>   	trace_xe_vm_free(vm);
>   	dma_fence_put(vm->rebind_fence);
>   	dma_resv_fini(&vm->resv);
>   	kfree(vm);
> -
>   }
>   
>   void xe_vm_free(struct kref *ref)