From: Satyanarayana K V P <satyanarayana.k.v.p@intel.com>

The migrate VM builds the CCS metadata save/restore batch buffer (BB) in
advance and retains it so the GuC can submit it directly when saving a
VM’s state.

Had to read the "migrate VM" part multiple times to understand it. Also maybe my idea on English is wrong, but 'retains' does not convey 'updates' for me. Maybe:

---
A VF driver with VM migration capability builds the CCS metadata save/restore batch buffer (BB) in
advance and keeps its content up to date so the GuC can submit it directly when saving a
VM’s state.

---
-Tomasz

When a VM migrates between VFs, the GGTT base can change. Any GGTT-based
addresses embedded in the BB would then have to be parsed and patched.

Use PPGTT addresses in the BB (including for TLB invalidation) so the BB
remains GGTT-agnostic and requires no address fixups during migration.

Signed-off-by: Satyanarayana K V P <satyanarayana.k.v.p@intel.com>
Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
---
 drivers/gpu/drm/xe/xe_migrate.c | 28 ++++++++++++++++++++--------
 1 file changed, 20 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/drm/xe/xe_migrate.c b/drivers/gpu/drm/xe/xe_migrate.c
index 1d667fa36cf3..ad03afb5145f 100644
--- a/drivers/gpu/drm/xe/xe_migrate.c
+++ b/drivers/gpu/drm/xe/xe_migrate.c
@@ -980,15 +980,27 @@ struct xe_lrc *xe_migrate_lrc(struct xe_migrate *migrate)
 	return migrate->q->lrc[0];
 }
 
-static int emit_flush_invalidate(struct xe_exec_queue *q, u32 *dw, int i,
-				 u32 flags)
+static u64 migrate_vm_ppgtt_addr_tlb_inval(void)
 {
-	struct xe_lrc *lrc = xe_exec_queue_lrc(q);
+	/*
+	 * The migrate VM is self-referential so it can modify its own PTEs (see
+	 * pte_update_size() or emit_pte() functions). We reserve NUM_KERNEL_PDE
+	 * entries for kernel operations (copies, clears, CCS migrate), and
+	 * suballocate the rest to user operations (binds/unbinds). With
+	 * NUM_KERNEL_PDE = 15, NUM_KERNEL_PDE - 1 is already used for PTE updates,
+	 * so assign NUM_KERNEL_PDE - 2 for TLB invalidation.
+	 */
+	return (NUM_KERNEL_PDE - 2) * XE_PAGE_SIZE;
+}
+
+static int emit_flush_invalidate(u32 *dw, int i, u32 flags)
+{
+	u64 addr = migrate_vm_ppgtt_addr_tlb_inval();
+
 	dw[i++] = MI_FLUSH_DW | MI_INVALIDATE_TLB | MI_FLUSH_DW_OP_STOREDW |
 		  MI_FLUSH_IMM_DW | flags;
-	dw[i++] = lower_32_bits(xe_lrc_start_seqno_ggtt_addr(lrc)) |
-		  MI_FLUSH_DW_USE_GTT;
-	dw[i++] = upper_32_bits(xe_lrc_start_seqno_ggtt_addr(lrc));
+	dw[i++] = lower_32_bits(addr);
+	dw[i++] = upper_32_bits(addr);
 	dw[i++] = MI_NOOP;
 	dw[i++] = MI_NOOP;
 
@@ -1101,11 +1113,11 @@ int xe_migrate_ccs_rw_copy(struct xe_tile *tile, struct xe_exec_queue *q,
 
 		emit_pte(m, bb, ccs_pt, false, false, &ccs_it, ccs_size, src);
 
-		bb->len = emit_flush_invalidate(q, bb->cs, bb->len, flush_flags);
+		bb->len = emit_flush_invalidate(bb->cs, bb->len, flush_flags);
 		flush_flags = xe_migrate_ccs_copy(m, bb, src_L0_ofs, src_is_pltt,
 						  src_L0_ofs, dst_is_pltt,
 						  src_L0, ccs_ofs, true);
-		bb->len = emit_flush_invalidate(q, bb->cs, bb->len, flush_flags);
+		bb->len = emit_flush_invalidate(bb->cs, bb->len, flush_flags);
 
 		size -= src_L0;
 	}