Re: [PATCH v6 09/12] drm/xe/dma_buf: Block export of DONTNEED/purged BOs

Yadav, Arvind
2026-03-18T13:02:35Z

On 10-03-2026 15:49, Thomas Hellström wrote:
> On Tue, 2026-03-03 at 20:50 +0530, Arvind Yadav wrote:
>> Don't allow exporting BOs marked DONTNEED or PURGED as dma-bufs.
>> DONTNEED BOs can have their contents discarded at any time, making
>> the exported dma-buf unusable for external devices. PURGED BOs have
>> no backing store and are permanently invalid.
>>
>> Return -EBUSY for DONTNEED BOs (temporary purgeable state) and
>> -EINVAL for purged BOs (permanent, no backing store).
>>
>> The export path now checks the BO's purgeable state before creating
>> the dma-buf, preventing external devices from accessing memory that
>> may be purged at any time.
>>
>> v6:
>> - Split DONTNEED → -EBUSY and PURGED → -EINVAL for consistency
>>   with the rest of the series (Thomas, Matt)
>>
>> Cc: Matthew Brost <matthew.brost@intel.com>
>> Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
>> Cc: Himal Prasad Ghimiray <himal.prasad.ghimiray@intel.com>
>> Signed-off-by: Arvind Yadav <arvind.yadav@intel.com>
>> ---
>>  drivers/gpu/drm/xe/xe_dma_buf.c | 21 +++++++++++++++++++++
>>  1 file changed, 21 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/xe/xe_dma_buf.c
>> b/drivers/gpu/drm/xe/xe_dma_buf.c
>> index ea370cd373e9..aba6b9696030 100644
>> --- a/drivers/gpu/drm/xe/xe_dma_buf.c
>> +++ b/drivers/gpu/drm/xe/xe_dma_buf.c
>> @@ -223,6 +223,23 @@ struct dma_buf *xe_gem_prime_export(struct
>> drm_gem_object *obj, int flags)
>>   if (bo->vm)
>>   return ERR_PTR(-EPERM);
>>
>> + /*
>> + * Reject exporting purgeable BOs. DONTNEED BOs can be
>> purged
>> + * at any time, making the exported dma-buf unusable. Purged
>> BOs
>> + * have no backing store and are permanently invalid.
>> + */
>> + xe_bo_lock(bo, false);
> Interruptible lock.

Noted,

~Arvind

>
> /Thomas
>
>
>> + if (xe_bo_madv_is_dontneed(bo)) {
>> + ret = -EBUSY;
>> + goto out_unlock;
>> + }
>> +
>> + if (xe_bo_is_purged(bo)) {
>> + ret = -EINVAL;
>> + goto out_unlock;
>> + }
>> + xe_bo_unlock(bo);
>> +
>>   ret = ttm_bo_setup_export(&bo->ttm, &ctx);
>>   if (ret)
>>   return ERR_PTR(ret);
>> @@ -232,6 +249,10 @@ struct dma_buf *xe_gem_prime_export(struct
>> drm_gem_object *obj, int flags)
>>   buf->ops = &xe_dmabuf_ops;
>>
>>   return buf;
>> +
>> +out_unlock:
>> + xe_bo_unlock(bo);
>> + return ERR_PTR(ret);
>>  }
>>
>>  static struct drm_gem_object *