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

["Yadav, Arvind" <arvind.yadav@intel.com>]

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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

>
> 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
>>

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