Commit eff8cbf0 authored by Philip Yang's avatar Philip Yang Committed by Alex Deucher
Browse files

drm/amdkfd: AIP mGPUs best prefetch location for xnack on 



For xnack on, if range ACCESS or ACCESS_IN_PLACE (AIP) by single GPU, or
range is ACCESS_IN_PLACE by mGPUs and all mGPUs connection on XGMI same
hive, the best prefetch location is prefetch_loc GPU. Otherwise, the best
prefetch location is always CPU because GPU does not have coherent
mapping VRAM of other GPUs even with large-BAR PCIe connection.

Signed-off-by: default avatarPhilip Yang <Philip.Yang@amd.com>
Reviewed-by: default avatarFelix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: default avatarAlex Deucher <alexander.deucher@amd.com>
parent f5bd5239

drivers/gpu/drm/amd/amdkfd/kfd_svm.c

+19 −16
Original line number Diff line number Diff line
@@ -2675,22 +2675,26 @@ svm_range_add(struct kfd_process *p, uint64_t start, uint64_t size, 
	return 0;

}



/* svm_range_best_prefetch_location - decide the best prefetch location

/**

 * svm_range_best_prefetch_location - decide the best prefetch location

 * @prange: svm range structure

 *

 * For xnack off:

 * If range map to single GPU, the best acutal location is prefetch loc, which

 * If range map to single GPU, the best prefetch location is prefetch_loc, which

 * can be CPU or GPU.

 *

 * If range map to multiple GPUs, only if mGPU connection on xgmi same hive,

 * the best actual location could be prefetch_loc GPU. If mGPU connection on

 * PCIe, the best actual location is always CPU, because GPU cannot access vram

 * of other GPUs, assuming PCIe small bar (large bar support is not upstream).

 * If range is ACCESS or ACCESS_IN_PLACE by mGPUs, only if mGPU connection on

 * XGMI same hive, the best prefetch location is prefetch_loc GPU, othervise

 * the best prefetch location is always CPU, because GPU can not have coherent

 * mapping VRAM of other GPUs even with large-BAR PCIe connection.

 *

 * For xnack on:

 * The best actual location is prefetch location. If mGPU connection on xgmi

 * same hive, range map to multiple GPUs. Otherwise, the range only map to

 * actual location GPU. Other GPU access vm fault will trigger migration.

 * If range is not ACCESS_IN_PLACE by mGPUs, the best prefetch location is

 * prefetch_loc, other GPU access will generate vm fault and trigger migration.

 *

 * If range is ACCESS_IN_PLACE by mGPUs, only if mGPU connection on XGMI same

 * hive, the best prefetch location is prefetch_loc GPU, otherwise the best

 * prefetch location is always CPU.

 *

 * Context: Process context

 *
@@ -2710,11 +2714,6 @@ svm_range_best_prefetch_location(struct svm_range *prange) 


	p = container_of(prange->svms, struct kfd_process, svms);



	/* xnack on */

	if (p->xnack_enabled)

		goto out;



	/* xnack off */

	if (!best_loc || best_loc == KFD_IOCTL_SVM_LOCATION_UNDEFINED)

		goto out;
@@ -2724,6 +2723,10 @@ svm_range_best_prefetch_location(struct svm_range *prange) 
		best_loc = 0;

		goto out;

	}



	if (p->xnack_enabled)

		bitmap_copy(bitmap, prange->bitmap_aip, MAX_GPU_INSTANCE);

	else

		bitmap_or(bitmap, prange->bitmap_access, prange->bitmap_aip,

			  MAX_GPU_INSTANCE);