Re: [PATCH v3 08/19] drm/xe/svm: Add xe_svm_ranges_zap_ptes_in_range() for PTE zapping

["Ghimiray, Himal Prasad" <himal.prasad.ghimiray@intel.com>]

On 29-05-2025 04:45, Matthew Brost wrote:
> On Tue, May 27, 2025 at 10:09:52PM +0530, Himal Prasad Ghimiray wrote:
>> Introduce xe_svm_ranges_zap_ptes_in_range(), a function to zap page table
>> entries (PTEs) for all SVM ranges within a user-specified address range.
>>
>> Signed-off-by: Himal Prasad Ghimiray <himal.prasad.ghimiray@intel.com>
>> ---
>>   drivers/gpu/drm/xe/xe_svm.c | 43 +++++++++++++++++++++++++++++++++++++
>>   drivers/gpu/drm/xe/xe_svm.h |  7 ++++++
>>   2 files changed, 50 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/xe/xe_svm.c b/drivers/gpu/drm/xe/xe_svm.c
>> index 59e73187114d..a4d53c24fcbc 100644
>> --- a/drivers/gpu/drm/xe/xe_svm.c
>> +++ b/drivers/gpu/drm/xe/xe_svm.c
>> @@ -1006,6 +1006,49 @@ int xe_svm_range_get_pages(struct xe_vm *vm, struct xe_svm_range *range,
>>   	return err;
>>   }
>>   
>> +/**
>> + * xe_svm_ranges_zap_ptes_in_range - clear ptes of svm ranges in input range
>> + * @vm: Pointer to the xe_vm structure
>> + * @start: Start of the input range
>> + * @end: End of the input range
>> + *
>> + * This function removes the page table entries (PTEs) associated
>> + * with the svm ranges within the given input start amnd end
>> + *
>> + * Return: tile_mask for which gt's need to be tlb invalidated.
>> + */
>> +u8 xe_svm_ranges_zap_ptes_in_range(struct xe_vm *vm, u64 start, u64 end)
>> +{
>> +	struct drm_gpusvm_notifier *notifier;
>> +	struct xe_svm_range *range;
>> +	u64 adj_start, adj_end;
>> +	struct xe_tile *tile;
>> +	u8 tile_mask = 0;
>> +	u8 id;
>> +
>> +	down_write(&vm->svm.gpusvm.notifier_lock);
> 
> xe_svm_notifier_lock

xe_pt_zap_ptes_range needs write_lock, whereas 
xe_svm_notifier_lock/unlock provides read lock.
  >
>> +
>> +	drm_gpusvm_for_each_notifier(notifier, &vm->svm.gpusvm, start, end) {
>> +		struct drm_gpusvm_range *r = NULL;
>> +
>> +		adj_start = max(start, notifier->itree.start);
>> +		adj_end = min(end, notifier->itree.last + 1);
>> +		drm_gpusvm_for_each_range(r, notifier, adj_start, adj_end) {
>> +			range = to_xe_range(r);
>> +			for_each_tile(tile, vm->xe, id) {
>> +				if (xe_pt_zap_ptes_range(tile, vm, range)) {
>> +					tile_mask |= BIT(id);
>> +					range->tile_invalidated |= BIT(id);
>> +				}
>> +			}
>> +		}
>> +	}
>> +
>> +	up_write(&vm->svm.gpusvm.notifier_lock);
>> +
> 
> xe_svm_notifier_unlock
> 
> Matt
> 
>> +	return tile_mask;
>> +}
>> +
>>   #if IS_ENABLED(CONFIG_DRM_XE_DEVMEM_MIRROR)
>>   
>>   static struct drm_pagemap_device_addr
>> diff --git a/drivers/gpu/drm/xe/xe_svm.h b/drivers/gpu/drm/xe/xe_svm.h
>> index 19ce4f2754a7..af8f285b6caa 100644
>> --- a/drivers/gpu/drm/xe/xe_svm.h
>> +++ b/drivers/gpu/drm/xe/xe_svm.h
>> @@ -91,6 +91,7 @@ bool xe_svm_range_validate(struct xe_vm *vm,
>>   
>>   u64 xe_svm_find_vma_start(struct xe_vm *vm, u64 addr, u64 end,  struct xe_vma *vma);
>>   
>> +u8 xe_svm_ranges_zap_ptes_in_range(struct xe_vm *vm, u64 start, u64 end);
>>   /**
>>    * xe_svm_range_has_dma_mapping() - SVM range has DMA mapping
>>    * @range: SVM range
>> @@ -305,6 +306,12 @@ u64 xe_svm_find_vma_start(struct xe_vm *vm, u64 addr, u64 end, struct xe_vma *vm
>>   	return ULONG_MAX;
>>   }
>>   
>> +static inline
>> +u8 xe_svm_ranges_zap_ptes_in_range(struct xe_vm *vm, u64 start, u64 end)
>> +{
>> +	return 0;
>> +}
>> +
>>   #define xe_svm_assert_in_notifier(...) do {} while (0)
>>   #define xe_svm_range_has_dma_mapping(...) false
>>   
>> -- 
>> 2.34.1
>>