[PATCH v2] drm/xe/guc: Add devm release action to safely tear down CT

[Satyanarayana K V P]

When a buffer object (BO) is allocated with the XE_BO_FLAG_GGTT_INVALIDATE
flag, the driver initiates TLB invalidation requests via the CTB mechanism
while releasing the BO. However a premature release of the CTB BO can lead
to system crashes, as observed in:

Oops: Oops: 0000 [#1] SMP NOPTI
RIP: 0010:h2g_write+0x2f3/0x7c0 [xe]
Call Trace:
 guc_ct_send_locked+0x8b/0x670 [xe]
 xe_guc_ct_send_locked+0x19/0x60 [xe]
 send_tlb_invalidation+0xb4/0x460 [xe]
 xe_gt_tlb_invalidation_ggtt+0x15e/0x2e0 [xe]
 ggtt_invalidate_gt_tlb.part.0+0x16/0x90 [xe]
 ggtt_node_remove+0x110/0x140 [xe]
 xe_ggtt_node_remove+0x40/0xa0 [xe]
 xe_ggtt_remove_bo+0x87/0x250 [xe]

Introduce a devm-managed release action during xe_guc_ct_init() to ensure
proper CTB disablement before resource deallocation, preventing the
use-after-free scenario.

Signed-off-by: Satyanarayana K V P <satyanarayana.k.v.p at intel.com>
Cc: Michal Wajdeczko <michal.wajdeczko at intel.com>
Cc: Matthew Brost <matthew.brost at intel.com>
Cc: Matthew Auld <matthew.auld at intel.com>
Cc: Summers Stuart <stuart.summers at intel.com>
Reviewed-by: Matthew Brost <matthew.brost at intel.com>

---
V1 -> V2:
- Fixed review comments (Michal & Matt B).
---
 drivers/gpu/drm/xe/xe_guc.c    | 21 ++++++++++++++++-----
 drivers/gpu/drm/xe/xe_guc_ct.c | 22 +++++++++++++++++++++-
 drivers/gpu/drm/xe/xe_guc_ct.h |  2 ++
 3 files changed, 39 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/xe/xe_guc.c b/drivers/gpu/drm/xe/xe_guc.c
index 433abc787f7b..5a6840d890f1 100644
--- a/drivers/gpu/drm/xe/xe_guc.c
+++ b/drivers/gpu/drm/xe/xe_guc.c
@@ -680,6 +680,21 @@ void xe_guc_comm_init_early(struct xe_guc *guc)
 		guc->notify_reg = GUC_HOST_INTERRUPT;
 }
 
+static int guc_realloc_ctb_vram(struct xe_guc *guc)
+{
+	struct xe_tile *tile = gt_to_tile(guc_to_gt(guc));
+	struct xe_device *xe = guc_to_xe(guc);
+	int ret;
+
+	ret = xe_managed_bo_reinit_in_vram(xe, tile, &guc->ct.bo);
+	if (ret)
+		return ret;
+
+	ret = xe_guc_action_disable_ct(&guc->ct);
+
+	return ret;
+}
+
 static int xe_guc_realloc_post_hwconfig(struct xe_guc *guc)
 {
 	struct xe_tile *tile = gt_to_tile(guc_to_gt(guc));
@@ -701,11 +716,7 @@ static int xe_guc_realloc_post_hwconfig(struct xe_guc *guc)
 	if (ret)
 		return ret;
 
-	ret = xe_managed_bo_reinit_in_vram(xe, tile, &guc->ct.bo);
-	if (ret)
-		return ret;
-
-	return 0;
+	return guc_realloc_ctb_vram(guc);
 }
 
 static int vf_guc_init_noalloc(struct xe_guc *guc)
diff --git a/drivers/gpu/drm/xe/xe_guc_ct.c b/drivers/gpu/drm/xe/xe_guc_ct.c
index 3f4e6a46ff16..fe844cfedd24 100644
--- a/drivers/gpu/drm/xe/xe_guc_ct.c
+++ b/drivers/gpu/drm/xe/xe_guc_ct.c
@@ -39,6 +39,8 @@ static void receive_g2h(struct xe_guc_ct *ct);
 static void g2h_worker_func(struct work_struct *w);
 static void safe_mode_worker_func(struct work_struct *w);
 static void ct_exit_safe_mode(struct xe_guc_ct *ct);
+static void guc_ct_change_state(struct xe_guc_ct *ct,
+				enum xe_guc_ct_state state);
 
 #if IS_ENABLED(CONFIG_DRM_XE_DEBUG)
 enum {
@@ -252,6 +254,23 @@ int xe_guc_ct_init_noalloc(struct xe_guc_ct *ct)
 }
 ALLOW_ERROR_INJECTION(xe_guc_ct_init_noalloc, ERRNO); /* See xe_pci_probe() */
 
+static void guc_action_disable_ct(void *arg)
+{
+	struct xe_guc_ct *ct = arg;
+
+	guc_ct_change_state(ct, XE_GUC_CT_STATE_DISABLED);
+}
+
+int xe_guc_action_disable_ct(struct xe_guc_ct *ct)
+{
+	struct xe_device *xe = ct_to_xe(ct);
+
+	if (devm_is_action_added(xe->drm.dev, guc_action_disable_ct, ct))
+		devm_release_action(xe->drm.dev, guc_action_disable_ct, ct);
+
+	return devm_add_action_or_reset(xe->drm.dev, guc_action_disable_ct, ct);
+}
+
 int xe_guc_ct_init(struct xe_guc_ct *ct)
 {
 	struct xe_device *xe = ct_to_xe(ct);
@@ -268,7 +287,8 @@ int xe_guc_ct_init(struct xe_guc_ct *ct)
 		return PTR_ERR(bo);
 
 	ct->bo = bo;
-	return 0;
+
+	return xe_guc_action_disable_ct(ct);
 }
 ALLOW_ERROR_INJECTION(xe_guc_ct_init, ERRNO); /* See xe_pci_probe() */
 
diff --git a/drivers/gpu/drm/xe/xe_guc_ct.h b/drivers/gpu/drm/xe/xe_guc_ct.h
index 18d4225e6502..6be5c3bc5562 100644
--- a/drivers/gpu/drm/xe/xe_guc_ct.h
+++ b/drivers/gpu/drm/xe/xe_guc_ct.h
@@ -73,4 +73,6 @@ xe_guc_ct_send_block_no_fail(struct xe_guc_ct *ct, const u32 *action, u32 len)
 
 long xe_guc_ct_queue_proc_time_jiffies(struct xe_guc_ct *ct);
 
+int xe_guc_action_disable_ct(struct xe_guc_ct *ct);
+
 #endif
-- 
2.43.0