On 8/15/2021 10:38 AM, Christoph Hellwig wrote:
On Fri, Aug 13, 2021 at 01:31:42AM -0500, Alex Sierra wrote:
migrate.vma = vma; migrate.start = start; migrate.end = end;
- migrate.flags = MIGRATE_VMA_SELECT_DEVICE_PRIVATE; migrate.pgmap_owner = SVM_ADEV_PGMAP_OWNER(adev);
- if (adev->gmc.xgmi.connected_to_cpu)
migrate.flags = MIGRATE_VMA_SELECT_SYSTEM;- else
migrate.flags = MIGRATE_VMA_SELECT_DEVICE_PRIVATE;It's been a while since I touched this migrate code, but doesn't this mean that if the range already contains system memory the migration now won't do anything? for the connected_to_cpu case?
For above’s condition equal to connected_to_cpu , we’re explicitly migrating from device memory to system memory with device generic type. In this type, device PTEs are present in CPU page table.
During migrate_vma_collect_pmd walk op at migrate_vma_setup call, there’s a condition for present pte that require migrate->flags be set for MIGRATE_VMA_SELECT_SYSTEM. Otherwise, the migration for this entry will be ignored.
Regards, Alex S.