[PATCH v3 17/25] drm/xe: Add device flag to enable PT mirroring across tiles

Matthew Brost
2026-02-28T01:35:33Z

Some multi-tile devices may want to mirror page tables across tiles for
memory-bandwidth reasons, while others may not. Add a device flag that
allows enabling or disabling page-table mirroring across tiles.

Setting the flag to true (the existing behavior) on PVC, but both modes
have been tested and are working on PVC.

Signed-off-by: Matthew Brost <matthew.brost@intel.com>
---
drivers/gpu/drm/xe/xe_device_types.h | 2 ++
drivers/gpu/drm/xe/xe_migrate.c | 5 ++--
drivers/gpu/drm/xe/xe_pci.c | 2 ++
drivers/gpu/drm/xe/xe_pci_types.h | 1 +
drivers/gpu/drm/xe/xe_pt.c | 38 ++++++++++++++++++++++++++--
drivers/gpu/drm/xe/xe_vm.c | 37 ++++++++++++++++++++++++---
drivers/gpu/drm/xe/xe_vm.h | 3 +++
7 files changed, 80 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/drm/xe/xe_device_types.h b/drivers/gpu/drm/xe/xe_device_types.h
index 776e9e190320..b3737dfcc45c 100644
--- a/drivers/gpu/drm/xe/xe_device_types.h
+++ b/drivers/gpu/drm/xe/xe_device_types.h
@@ -208,6 +208,8 @@ struct xe_device {
u8 has_usm:1;
/** @info.has_64bit_timestamp: Device supports 64-bit timestamps */
u8 has_64bit_timestamp:1;
+ /** @info.has_pt_mirror: Device has PT mirroring across tiles */
+ u8 has_pt_mirror:1;
/** @info.is_dgfx: is discrete device */
u8 is_dgfx:1;
/** @info.needs_scratch: needs scratch page for oob prefetch to work */
diff --git a/drivers/gpu/drm/xe/xe_migrate.c b/drivers/gpu/drm/xe/xe_migrate.c
index b5d4fc4d4c62..c9ee6325ec9d 100644
--- a/drivers/gpu/drm/xe/xe_migrate.c
+++ b/drivers/gpu/drm/xe/xe_migrate.c
@@ -183,7 +183,8 @@ static int xe_migrate_prepare_vm(struct xe_tile *tile, struct xe_migrate *m,
struct xe_device *xe = tile_to_xe(tile);
u16 pat_index = xe->pat.idx[XE_CACHE_WB];
u8 id = tile->id;
- u32 num_entries = NUM_PT_SLOTS, num_level = vm->pt_root[id]->level;
+ u32 num_entries = NUM_PT_SLOTS, num_level =
+ xe_vm_pt_root(vm, id)->level;
#define VRAM_IDENTITY_MAP_COUNT 2
u32 num_setup = num_level + VRAM_IDENTITY_MAP_COUNT;
#undef VRAM_IDENTITY_MAP_COUNT
@@ -210,7 +211,7 @@ static int xe_migrate_prepare_vm(struct xe_tile *tile, struct xe_migrate *m,
/* PT30 & PT31 reserved for 2M identity map */
pt29_ofs = xe_bo_size(bo) - 3 * XE_PAGE_SIZE;
entry = vm->pt_ops->pde_encode_bo(bo, pt29_ofs);
- xe_pt_write(xe, &vm->pt_root[id]->bo->vmap, 0, entry);
+ xe_pt_write(xe, &xe_vm_pt_root(vm, id)->bo->vmap, 0, entry);

map_ofs = (num_entries - num_setup) * XE_PAGE_SIZE;

diff --git a/drivers/gpu/drm/xe/xe_pci.c b/drivers/gpu/drm/xe/xe_pci.c
index 3ac99472d6dd..b8c8953833a5 100644
--- a/drivers/gpu/drm/xe/xe_pci.c
+++ b/drivers/gpu/drm/xe/xe_pci.c
@@ -352,6 +352,7 @@ static const __maybe_unused struct xe_device_desc pvc_desc = {
.dma_mask_size = 52,
.has_display = false,
.has_gsc_nvm = 1,
+ .has_pt_mirror = 1,
.has_heci_gscfi = 1,
.max_gt_per_tile = 1,
.max_remote_tiles = 1,
@@ -761,6 +762,7 @@ static int xe_info_init_early(struct xe_device *xe,
xe->info.has_soc_remapper_telem = desc->has_soc_remapper_telem;
xe->info.has_sriov = xe_configfs_primary_gt_allowed(to_pci_dev(xe->drm.dev)) &&
desc->has_sriov;
+ xe->info.has_pt_mirror = desc->has_pt_mirror;
xe->info.skip_guc_pc = desc->skip_guc_pc;
xe->info.skip_mtcfg = desc->skip_mtcfg;
xe->info.skip_pcode = desc->skip_pcode;
diff --git a/drivers/gpu/drm/xe/xe_pci_types.h b/drivers/gpu/drm/xe/xe_pci_types.h
index 47e8a1552c2b..14b688fbb4c1 100644
--- a/drivers/gpu/drm/xe/xe_pci_types.h
+++ b/drivers/gpu/drm/xe/xe_pci_types.h
@@ -57,6 +57,7 @@ struct xe_device_desc {
u8 has_soc_remapper_sysctrl:1;
u8 has_soc_remapper_telem:1;
u8 has_sriov:1;
+ u8 has_pt_mirror:1;
u8 needs_scratch:1;
u8 skip_guc_pc:1;
u8 skip_mtcfg:1;
diff --git a/drivers/gpu/drm/xe/xe_pt.c b/drivers/gpu/drm/xe/xe_pt.c
index d91d80c92957..ef34fbfc14f0 100644
--- a/drivers/gpu/drm/xe/xe_pt.c
+++ b/drivers/gpu/drm/xe/xe_pt.c
@@ -734,7 +734,7 @@ xe_pt_stage_bind(struct xe_tile *tile, struct xe_vma *vma,
.wupd.entries = entries,
.clear_pt = clear_pt,
};
- struct xe_pt *pt = vm->pt_root[tile->id];
+ struct xe_pt *pt = xe_vm_pt_root(vm, tile->id);
int ret;

if (range) {
@@ -895,6 +895,11 @@ static int xe_pt_zap_ptes_entry(struct xe_ptw *parent, pgoff_t offset,
return 0;
}

+static bool pt_mirroring_disabled_for_tile(struct xe_vm *vm, u8 tile_id)
+{
+ return xe_vm_pt_root(vm, tile_id) != vm->pt_root[tile_id];
+}
+
static const struct xe_pt_walk_ops xe_pt_zap_ptes_ops = {
.pt_entry = xe_pt_zap_ptes_entry,
};
@@ -936,6 +941,9 @@ bool xe_pt_zap_ptes(struct xe_tile *tile, struct xe_vma *vma)
if (!(pt_mask & BIT(tile->id)))
return false;

+ if (pt_mirroring_disabled_for_tile(xe_vma_vm(vma), tile->id))
+ return true;
+
(void)xe_pt_walk_shared(&pt->base, pt->level, xe_vma_start(vma),
xe_vma_end(vma), &xe_walk.base);

@@ -988,6 +996,9 @@ bool xe_pt_zap_ptes_range(struct xe_tile *tile, struct xe_vm *vm,
if (!(pt_mask & BIT(tile->id)))
return false;

+ if (pt_mirroring_disabled_for_tile(vm, tile->id))
+ return true;
+
(void)xe_pt_walk_shared(&pt->base, pt->level, xe_svm_range_start(range),
xe_svm_range_end(range), &xe_walk.base);

@@ -1803,7 +1814,7 @@ static unsigned int xe_pt_stage_unbind(struct xe_tile *tile,
.wupd.entries = entries,
.prl = pt_update_op->prl,
};
- struct xe_pt *pt = vm->pt_root[tile->id];
+ struct xe_pt *pt = xe_vm_pt_root(vm, tile->id);

(void)xe_pt_walk_shared(&pt->base, pt->level, start, end,
&xe_walk.base);
@@ -2341,9 +2352,20 @@ int xe_pt_update_ops_prepare(struct xe_device *xe, struct xe_vma_ops *vops)
int id, err;

for_each_tile(tile, xe, id) {
+ struct xe_vm_pgtable_update_ops *pt_update_ops =
+ &vops->pt_update_ops[id];
+
if (!vops->pt_update_ops[id].num_ops)
continue;

+ if (pt_mirroring_disabled_for_tile(vops->vm, id)) {
+ struct xe_page_reclaim_list *prl = &pt_update_ops->prl;
+
+ /* Transfer root PT update ops PRL to current */
+ *prl = vops->pt_update_ops[0].prl;
+ continue;
+ }
+
err = __xe_pt_update_ops_prepare(tile, vops);
if (err)
return err;
@@ -2635,6 +2657,12 @@ xe_pt_update_ops_run(struct xe_device *xe, struct xe_vma_ops *vops)
struct xe_vm_pgtable_update_ops *pt_update_ops =
&vops->pt_update_ops[j];

+ if (pt_mirroring_disabled_for_tile(vm, j)) {
+ xe_tile_assert(tile, !get_current_op(pt_update_ops));
+ tile_mask |= BIT(tile->id);
+ continue;
+ }
+
for (i = 0; i < get_current_op(pt_update_ops); ++i) {
struct xe_vm_pgtable_update_op *pt_op =
to_pt_op(pt_update_ops, i);
@@ -2724,6 +2752,9 @@ void xe_pt_update_ops_fini(struct xe_device *xe, struct xe_vma_ops *vops)
if (!pt_update_ops->num_ops)
continue;

+ if (pt_mirroring_disabled_for_tile(vops->vm, id))
+ continue;
+
xe_page_reclaim_entries_put(pt_update_ops->prl.entries);
}
}
@@ -2748,6 +2779,9 @@ void xe_pt_update_ops_abort(struct xe_device *xe, struct xe_vma_ops *vops)
&vops->pt_update_ops[id];
int i;

+ if (pt_mirroring_disabled_for_tile(vops->vm, id))
+ continue;
+
for (i = pt_update_ops->num_ops - 1; i >= 0; --i) {
struct xe_vm_pgtable_update_op *pt_op =
to_pt_op(pt_update_ops, i);
diff --git a/drivers/gpu/drm/xe/xe_vm.c b/drivers/gpu/drm/xe/xe_vm.c
index b3928e05b70a..d4629e953b01 100644
--- a/drivers/gpu/drm/xe/xe_vm.c
+++ b/drivers/gpu/drm/xe/xe_vm.c
@@ -738,6 +738,14 @@ int xe_vm_rebind(struct xe_vm *vm, bool rebind_worker)
return err;
}

+static u8 adjust_rebind_tile_mask(struct xe_vm *vm, u8 tile_mask)
+{
+ if (vm->xe->info.has_pt_mirror)
+ return tile_mask;
+
+ return (0x1 << vm->xe->info.max_gt_per_tile) - 1;
+}
+
struct dma_fence *xe_vma_rebind(struct xe_vm *vm, struct xe_vma *vma, u8 tile_mask)
{
struct dma_fence *fence = NULL;
@@ -754,7 +762,8 @@ struct dma_fence *xe_vma_rebind(struct xe_vm *vm, struct xe_vma *vma, u8 tile_ma
vops.flags |= XE_VMA_OPS_FLAG_SKIP_TLB_WAIT |
XE_VMA_OPS_FLAG_WAIT_VM_BOOKKEEP;

- err = xe_vm_ops_add_rebind(&vops, vma, tile_mask);
+ err = xe_vm_ops_add_rebind(&vops, vma,
+ adjust_rebind_tile_mask(vm, tile_mask));
if (err)
return ERR_PTR(err);

@@ -840,7 +849,8 @@ struct dma_fence *xe_vm_range_rebind(struct xe_vm *vm,
vops.flags |= XE_VMA_OPS_FLAG_SKIP_TLB_WAIT |
XE_VMA_OPS_FLAG_WAIT_VM_BOOKKEEP;

- err = xe_vm_ops_add_range_rebind(&vops, vma, range, tile_mask);
+ err = xe_vm_ops_add_range_rebind(&vops, vma, range,
+ adjust_rebind_tile_mask(vm, tile_mask));
if (err)
return ERR_PTR(err);

@@ -1578,7 +1588,8 @@ 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,
@@ -1887,7 +1898,7 @@ struct xe_vm *xe_vm_lookup(struct xe_file *xef, u32 id)

u64 xe_vm_pdp4_descriptor(struct xe_vm *vm, struct xe_tile *tile)
{
- return vm->pt_ops->pde_encode_bo(vm->pt_root[tile->id]->bo, 0);
+ return vm->pt_ops->pde_encode_bo(xe_vm_pt_root(vm, tile->id)->bo, 0);
}

static struct xe_exec_queue *
@@ -4583,3 +4594,21 @@ void xe_vm_remove_exec_queue(struct xe_vm *vm, struct xe_exec_queue *q)
}
up_write(&vm->exec_queues.lock);
}
+
+/**
+ * xe_vm_pt_root() - Retrieve VM page-table root
+ * @vm: The VM.
+ * @tile_id: Tile ID
+ *
+ * Retrieve VM page-table root for a tile ID, used to abstract if PT mirroring is
+ * enabled across tiles.
+ *
+ * Return: VM page-table root for a tile ID
+ */
+struct xe_pt *xe_vm_pt_root(struct xe_vm *vm, u8 tile_id)
+{
+ if (vm->xe->info.has_pt_mirror)
+ return vm->pt_root[tile_id];
+
+ return vm->pt_root[0];
+}
diff --git a/drivers/gpu/drm/xe/xe_vm.h b/drivers/gpu/drm/xe/xe_vm.h
index f849e369432b..5a22f74ff332 100644
--- a/drivers/gpu/drm/xe/xe_vm.h
+++ b/drivers/gpu/drm/xe/xe_vm.h
@@ -425,4 +425,7 @@ static inline struct drm_exec *xe_vm_validation_exec(struct xe_vm *vm)
((READ_ONCE(tile_present) & ~READ_ONCE(tile_invalidated)) & BIT((tile)->id))

void xe_vma_mem_attr_copy(struct xe_vma_mem_attr *to, struct xe_vma_mem_attr *from);
+
+struct xe_pt *xe_vm_pt_root(struct xe_vm *vm, u8 tile_id);
+
#endif
--
2.34.1