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

Yadav, Arvind
2026-01-23T05:42:01Z

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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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