Re: [RFC v2 2/9] drm/xe/bo: Add purgeable bo state tracking and field madv to xe_bo

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

On 02-12-2025 04:32, Matthew Brost wrote:
> On Mon, Dec 01, 2025 at 11:20:12AM +0530, Arvind Yadav wrote:
>> Add infrastructure for tracking purgeable state of buffer objects.
>> This includes:
>>
>> Introduce enum xe_madv_purgeable_state with three states:
>>     - XE_MADV_PURGEABLE_WILLNEED (0): BO is needed and should not be
>>       purged. This is the default state for all BOs.
>>
>>     - XE_MADV_PURGEABLE_DONTNEED (1): BO is not currently needed and
>>       can be purged by the kernel under memory pressure to reclaim
>>       resources. Only non-shared BOs can be marked as DONTNEED.
>>
>>     - XE_MADV_PURGEABLE_PURGED (2): BO has been purged by the kernel.
>>       Accessing a purged BO results in error. Follows i915 semantics
>>       where once purged, the BO remains permanently invalid ("once
>>       purged, always purged").
>>
>> Add atomic_t madv field to struct xe_bo for state tracking
>>    of purgeable state across concurrent access paths
>>
>> v2: Add xe_bo_is_purged() helper, improve state documentation
>>
>> 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_bo.h       | 27 +++++++++++++++++++++++++++
>>   drivers/gpu/drm/xe/xe_bo_types.h |  3 +++
>>   2 files changed, 30 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/xe/xe_bo.h b/drivers/gpu/drm/xe/xe_bo.h
>> index 911d5b90461a..b0a31c77e612 100644
>> --- a/drivers/gpu/drm/xe/xe_bo.h
>> +++ b/drivers/gpu/drm/xe/xe_bo.h
>> @@ -85,6 +85,28 @@
>>   
>>   #define XE_PCI_BARRIER_MMAP_OFFSET	(0x50 << XE_PTE_SHIFT)
>>   
>> +/**
>> + * enum xe_madv_purgeable_state - Buffer object purgeable state enumeration
>> + *
>> + * This enum defines the possible purgeable states for a buffer object,
>> + * allowing userspace to provide memory usage hints to the kernel for
>> + * better memory management under pressure.
>> + *
>> + * @XE_MADV_PURGEABLE_WILLNEED: The buffer object is needed and should not be purged.
>> + * This is the default state.
>> + * @XE_MADV_PURGEABLE_DONTNEED: The buffer object is not currently needed and can be
>> + * purged by the kernel under memory pressure.
>> + * @XE_MADV_PURGEABLE_PURGED: The buffer object has been purged by the kernel.
>> + *
>> + * Accessing a purged buffer will result in an error. Per i915 semantics,
>> + * once purged, a BO remains permanently invalid and must be destroyed and recreated.
>> + */
>> +enum xe_madv_purgeable_state {
>> +	XE_MADV_PURGEABLE_WILLNEED,
>> +	XE_MADV_PURGEABLE_DONTNEED,
>> +	XE_MADV_PURGEABLE_PURGED,
>> +};
>> +
>>   struct sg_table;
>>   
>>   struct xe_bo *xe_bo_alloc(void);
>> @@ -213,6 +235,11 @@ static inline bool xe_bo_is_protected(const struct xe_bo *bo)
>>   	return bo->pxp_key_instance;
>>   }
>>   
> Kernel doc.

Noted.

~Arvind

>
> Matt
>
>> +static inline bool xe_bo_is_purged(struct xe_bo *bo)
>> +{
>> +	return atomic_read(&bo->madv_purgeable) == XE_MADV_PURGEABLE_PURGED;
>> +}
>> +
>>   static inline void xe_bo_unpin_map_no_vm(struct xe_bo *bo)
>>   {
>>   	if (likely(bo)) {
>> diff --git a/drivers/gpu/drm/xe/xe_bo_types.h b/drivers/gpu/drm/xe/xe_bo_types.h
>> index d4fe3c8dca5b..57b4dc7012e2 100644
>> --- a/drivers/gpu/drm/xe/xe_bo_types.h
>> +++ b/drivers/gpu/drm/xe/xe_bo_types.h
>> @@ -108,6 +108,9 @@ struct xe_bo {
>>   	 * from default
>>   	 */
>>   	u64 min_align;
>> +
>> +	/** @madv_purgeable: user space advise on BO purgeability */
>> +	atomic_t madv_purgeable;
>>   };
>>   
>>   #endif
>> -- 
>> 2.43.0
>>