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Sashiko AI review found 1 potential issue(s) to consider: > > - [Medium] Unnecessary allocation of page table roots and scratch structures for secondary tiles when PT mirroring is disabled. > > Looks valid. > I'd didn't really want to over engineer this one and this wastes 4k of memory. Matt > > -- > > > > commit 34b539e899a7643dc15dedad6a3cd229e0c0f4d5 > > Author: Matthew Brost > > > > drm/xe: Add device flag to enable PT mirroring across tiles > > > > This commit introduces a device flag to toggle page-table mirroring across > > tiles for memory bandwidth considerations. It updates the VM creation, > > rebind, and page table update paths to check this flag and fall back to the > > primary tile's root page table when mirroring is disabled. > > > > Link: https://patch.msgid.link/20260228013501.106680-18-matthew.brost@intel.com > > > > > diff --git a/drivers/gpu/drm/xe/xe_vm.c b/drivers/gpu/drm/xe/xe_vm.c > > > --- a/drivers/gpu/drm/xe/xe_vm.c > > > +++ b/drivers/gpu/drm/xe/xe_vm.c > > > > [ ... ] > > > > > @@ -1738,7 +1748,8 @@ struct xe_vm *xe_vm_create(struct xe_device *xe, u32 flags, struct xe_file *xef) > > > for_each_tile(tile, xe, id) { > > > if (flags & XE_VM_FLAG_MIGRATION && > > > - tile->id != XE_VM_FLAG_TILE_ID(flags)) > > > + tile->id != XE_VM_FLAG_TILE_ID(flags) && > > > + (vm->xe->info.has_pt_mirror || id)) > > > continue; > > > vm->pt_root[id] = xe_pt_create(vm, tile, xe->info.vm_max_level, > > > > [Severity: Medium] > > Does this code unnecessarily allocate page table roots and scratch structures > > for secondary tiles when PT mirroring is disabled? > > > > For standard user VMs, XE_VM_FLAG_MIGRATION is unset, meaning this if > > condition evaluates to false and we proceed to allocate pt_root[id] for all > > tiles. > > > > However, when vm->xe->info.has_pt_mirror is false, xe_vm_pt_root() > > unconditionally returns pt_root[0]. This means the allocated pt_root[id] > > (and associated scratch page tables up to vm_max_level) for id > 0 will never > > be used, permanently wasting VRAM for the lifetime of every VM. > > > > Should there be an explicit check to skip secondary tile allocations when > > has_pt_mirror is false, regardless of whether it is a migration VM? > > >