Re: [PATCH v4 5/8] drm/xe/vm: Prevent binding of purged buffer objects

Yadav, Arvind
2026-01-30T08:18:16Z

On 23-01-2026 18:07, Thomas Hellström wrote:
> On Fri, 2026-01-23 at 11:11 +0530, Yadav, Arvind wrote:
>> On 20-01-2026 22:57, Matthew Brost wrote:
>>> On Tue, Jan 20, 2026 at 11:38:51AM +0530, Arvind Yadav wrote:
>>>> Add check_purged parameter to vma_lock_and_validate() to block
>>>> new mapping operations on purged BOs while allowing cleanup
>>>> operations to proceed.
>>>>
>>>> Purged BOs have their backing pages freed by the kernel. New
>>>> mapping operations (MAP, PREFETCH, REMAP) must be rejected with
>>>> -EINVAL to prevent GPU access to invalid memory. Cleanup
>>>> operations (UNMAP) must be allowed so applications can release
>>>> resources after detecting purge via the retained field.
>>>>
>>>> REMAP operations require mixed handling - reject new prev/next
>>>> VMAs if the BO is purged, but allow the unmap portion to proceed
>>>> for cleanup.
>>>>
>>>> The check_purged parameter distinguishes between these cases:
>>>> true for new mappings (must reject), false for cleanup (allow).
>>>>
>>>> v2:
>>>>    - Clarify that purged BOs are permanently invalid (i915
>>>> semantics)
>>>>    - Remove incorrect claim about madvise(WILLNEED) restoring
>>>> purged BOs
>>>>
>>>> v3:
>>>>    - Move xe_bo_is_purged check under vma_lock_and_validate
>>>> (Matthew Brost)
>>>>    - Add check_purged parameter to distinguish new mappings from
>>>> cleanup
>>>>    - Allow UNMAP operations to prevent resource leaks
>>>>    - Handle REMAP operation's dual nature (cleanup + new
>>>> mappings)
>>>>
>>>> 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_vm.c | 20 +++++++++++++-------
>>>>   1 file changed, 13 insertions(+), 7 deletions(-)
>>>>
>>>> diff --git a/drivers/gpu/drm/xe/xe_vm.c
>>>> b/drivers/gpu/drm/xe/xe_vm.c
>>>> index c3a5fe76ff96..f250daae3012 100644
>>>> --- a/drivers/gpu/drm/xe/xe_vm.c
>>>> +++ b/drivers/gpu/drm/xe/xe_vm.c
>>>> @@ -2883,7 +2883,7 @@ static void vm_bind_ioctl_ops_unwind(struct
>>>> xe_vm *vm,
>>>>   }
>>>>
>>>>   static int vma_lock_and_validate(struct drm_exec *exec, struct
>>>> xe_vma *vma,
>>>> - bool res_evict, bool validate)
>>>> + bool res_evict, bool validate,
>>>> bool check_purged)
>>> It probably time to add something like this to avoid transposing
>>> arguments.
>>>
>>> struct lock_and_validate_flags {
>>> bool res_evict;
>>> bool validate;
>>> bool check_purged;
>>> };
>>>
>>> Logic in the patch looks correct though.
>>
>> Noted, I will add "struct xe_lock_and_validate_flags" Thanks, Arvind
> Note that if you follow the pattern of struct xe_bo_shink_flags,
> passing the struct as a const and using
>
> struct lock_and_validate_flags {
> u32 res_evict : 1;
> u32 validate : 1;
> u32 check_purged : 1;
> };
>
> This will be more or less equivalent to passing a bit-field with type-
> checking.
>
> Some reviewers frown on using "bool" in compound types although we
> accept that in the xe driver.

Noted, I will do the changes as per suggestion..

Thanks,
Arvind

> Otherwise patch LGTM as well.
>
> /Thomas
>
>
>>> Matt
>>>
>>>>   {
>>>>    struct xe_bo *bo = xe_vma_bo(vma);
>>>>    struct xe_vm *vm = xe_vma_vm(vma);
>>>> @@ -2892,6 +2892,11 @@ static int vma_lock_and_validate(struct
>>>> drm_exec *exec, struct xe_vma *vma,
>>>>    if (bo) {
>>>>    if (!bo->vm)
>>>>    err = drm_exec_lock_obj(exec, &bo-
>>>>> ttm.base);
>>>> +
>>>> + /* Reject new mappings to purged BOs; allow
>>>> cleanup operations */
>>>> + if (!err && check_purged && xe_bo_is_purged(bo))
>>>> + err = -EINVAL;
>>>> +
>>>>    if (!err && validate)
>>>>    err = xe_bo_validate(bo, vm,
>>>>
>>>> !xe_vm_in_preempt_fence_mode(vm) &&
>>>> @@ -2990,7 +2995,8 @@ static int op_lock_and_prep(struct drm_exec
>>>> *exec, struct xe_vm *vm,
>>>>    err = vma_lock_and_validate(exec, op-
>>>>> map.vma,
>>>>        res_evict,
>>>>
>>>> !xe_vm_in_fault_mode(vm) ||
>>>> -     op-
>>>>> map.immediate);
>>>> +     op-
>>>>> map.immediate,
>>>> +     true);
>>>>    break;
>>>>    case DRM_GPUVA_OP_REMAP:
>>>>    err = check_ufence(gpuva_to_vma(op-
>>>>> base.remap.unmap->va));
>>>> @@ -2999,13 +3005,13 @@ static int op_lock_and_prep(struct
>>>> drm_exec *exec, struct xe_vm *vm,
>>>>
>>>>    err = vma_lock_and_validate(exec,
>>>>        gpuva_to_vma(op-
>>>>> base.remap.unmap->va),
>>>> -     res_evict, false);
>>>> +     res_evict, false,
>>>> false);
>>>>    if (!err && op->remap.prev)
>>>>    err = vma_lock_and_validate(exec, op-
>>>>> remap.prev,
>>>> -     res_evict,
>>>> true);
>>>> +     res_evict,
>>>> true, true);
>>>>    if (!err && op->remap.next)
>>>>    err = vma_lock_and_validate(exec, op-
>>>>> remap.next,
>>>> -     res_evict,
>>>> true);
>>>> +     res_evict,
>>>> true, true);
>>>>    break;
>>>>    case DRM_GPUVA_OP_UNMAP:
>>>>    err = check_ufence(gpuva_to_vma(op-
>>>>> base.unmap.va));
>>>> @@ -3014,7 +3020,7 @@ static int op_lock_and_prep(struct drm_exec
>>>> *exec, struct xe_vm *vm,
>>>>
>>>>    err = vma_lock_and_validate(exec,
>>>>        gpuva_to_vma(op-
>>>>> base.unmap.va),
>>>> -     res_evict, false);
>>>> +     res_evict, false,
>>>> false);
>>>>    break;
>>>>    case DRM_GPUVA_OP_PREFETCH:
>>>>    {
>>>> @@ -3029,7 +3035,7 @@ static int op_lock_and_prep(struct drm_exec
>>>> *exec, struct xe_vm *vm,
>>>>
>>>>    err = vma_lock_and_validate(exec,
>>>>        gpuva_to_vma(op-
>>>>> base.prefetch.va),
>>>> -     res_evict, false);
>>>> +     res_evict, false,
>>>> true);
>>>>    if (!err && !xe_vma_has_no_bo(vma))
>>>>    err = xe_bo_migrate(xe_vma_bo(vma),
>>>>
>>>> region_to_mem_type[region],
>>>> --
>>>> 2.43.0