[PATCH v2 11/32] drm/xe/svm: Add function to determine if range needs VRAM migration

[Ghimiray, Himal Prasad]

On 17-04-2025 08:35, Matthew Brost wrote:
> On Mon, Apr 07, 2025 at 03:46:58PM +0530, Himal Prasad Ghimiray wrote:
>> xe_svm_range_needs_migrate_to_vram() determines whether range needs
>> migration to vram or not, for pagefault try at least once.
>>
> 
> So I pulled this patch into requested series to minimally enable atomic
> on the existing upstream code here [1]. I suspect we will get my series
> in first, perhaps even in the 6.15 cycle as I think it could reasonably
> justified as a fixes series as the compute UMD doesn't really work
> without it. Just a heads up.

I will build upon the [1] so irrespective of which series lands first, 
there wont be any impact on another one.

[1] https://patchwork.freedesktop.org/patch/649010/?series=147846&rev=2

> 
> [1] https://patchwork.freedesktop.org/patch/647159/?series=146290&rev=4
> 
>> Signed-off-by: Himal Prasad Ghimiray <himal.prasad.ghimiray at intel.com>
>> ---
>>   drivers/gpu/drm/xe/xe_svm.c | 49 +++++++++++++++++++++++++++++++++++--
>>   drivers/gpu/drm/xe/xe_svm.h | 10 ++++++++
>>   2 files changed, 57 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/xe/xe_svm.c b/drivers/gpu/drm/xe/xe_svm.c
>> index 8cd35553a927..f4ae3feaf9d3 100644
>> --- a/drivers/gpu/drm/xe/xe_svm.c
>> +++ b/drivers/gpu/drm/xe/xe_svm.c
>> @@ -709,6 +709,51 @@ int xe_svm_alloc_vram(struct xe_vm *vm, struct xe_tile *tile,
>>   }
>>   #endif
>>   
>> +static bool supports_4K_migration(struct xe_device *xe)
>> +{
>> +	if (xe->info.platform == XE_BATTLEMAGE)
>> +		return true;
>> +
>> +	return false;
> 
> 	if (xe->info.vram_flags & XE_VRAM_FLAGS_NEED64K)
> 		return false;
> 
> 	return true;
> 
>> +}
>> +
>> +/**
>> + * xe_svm_range_needs_migrate_to_vram() - SVM range needs migrate to VRAM or not
>> + * @range: SVM range for which migration needs to be decided
>> + * @vma: vma which has range
>> + * @region: default placement for range
>> + *
>> + * Return: True for range needing migration and migration is supported else false
>> + */
>> +bool xe_svm_range_needs_migrate_to_vram(struct xe_svm_range *range, struct xe_vma *vma,
>> +					u32 region)
>> +{
>> +	struct xe_vm *vm = range_to_vm(&range->base);
>> +	u64 range_size = xe_svm_range_size(range);
>> +	bool needs_migrate = false;
>> +
>> +	if (!range->base.flags.migrate_devmem)
>> +		return false;
>> +
>> +	needs_migrate = region;
>> +
>> +	if (needs_migrate && !IS_DGFX(vm->xe)) {
>> +		drm_warn(&vm->xe->drm, "Platform doesn't support VRAM\n");
>> +		return false;
>> +	}
> 
> I'm not sure if this warrents a drm_warn, I think an assert would be
> better here as it shouldn't happen unless we have an internal
> programming error.

Sure.

> 
> Matt
> 
>> +
>> +	if (needs_migrate && xe_svm_range_in_vram(range)) {
>> +		drm_info(&vm->xe->drm, "Range is already in VRAM\n");
>> +		return false;
>> +	}
>> +
>> +	if (needs_migrate && range_size <= SZ_64K && !supports_4K_migration(vm->xe)) {
>> +		drm_warn(&vm->xe->drm, "Platform doesn't support SZ_4K range migration\n");
>> +		return false;
>> +	}
>> +
>> +	return needs_migrate;
>> +}
>>   
>>   /**
>>    * xe_svm_handle_pagefault() - SVM handle page fault
>> @@ -763,8 +808,8 @@ int xe_svm_handle_pagefault(struct xe_vm *vm, struct xe_vma *vma,
>>   	range_debug(range, "PAGE FAULT");
>>   
>>   	/* XXX: Add migration policy, for now migrate range once */
>> -	if (!range->skip_migrate && range->base.flags.migrate_devmem &&
>> -	    xe_svm_range_size(range) >= SZ_64K) {
>> +	if (!range->skip_migrate &&
>> +	    xe_svm_range_needs_migrate_to_vram(range, vma, IS_DGFX(vm->xe))) {
> 
> A little odd to pass IS_DGFX(vm->xe) as the region...

OK.

> 
>>   		range->skip_migrate = true;
>>   
>>   		err = xe_svm_alloc_vram(vm, tile, range, &ctx);
>> diff --git a/drivers/gpu/drm/xe/xe_svm.h b/drivers/gpu/drm/xe/xe_svm.h
>> index 9c4c3aeacc6c..d5be8229ca7e 100644
>> --- a/drivers/gpu/drm/xe/xe_svm.h
>> +++ b/drivers/gpu/drm/xe/xe_svm.h
>> @@ -95,6 +95,9 @@ struct xe_svm_range *xe_svm_range_find_or_insert(struct xe_vm *vm, u64 addr,
>>   int xe_svm_range_get_pages(struct xe_vm *vm, struct xe_svm_range *range,
>>   			   struct drm_gpusvm_ctx *ctx);
>>   
>> +bool xe_svm_range_needs_migrate_to_vram(struct xe_svm_range *range, struct xe_vma *vma,
>> +					u32 region);
>> +
>>   /**
>>    * xe_svm_range_has_dma_mapping() - SVM range has DMA mapping
>>    * @range: SVM range
>> @@ -281,6 +284,13 @@ static inline unsigned long xe_svm_range_size(struct xe_svm_range *range)
>>   	return 0;
>>   }
>>   
>> +static inline
>> +bool xe_svm_range_needs_migrate_to_vram(struct xe_svm_range *range, struct xe_vma *vma,
>> +					u32 region)
>> +{
>> +	return false;
>> +}
>> +
>>   #define xe_svm_assert_in_notifier(...) do {} while (0)
>>   #define xe_svm_range_has_dma_mapping(...) false
>>   
>> -- 
>> 2.34.1
>>