[PATCH 1/2] drm/xe/oa: Disallow OA from being enabled on active exec_queue's

[Ashutosh Dixit]

Enabling OA on an exec_queue toggles the OAC_CONTEXT_ENABLE bit in
CTXT_SR_CTL register. Toggling this bit changes the size and layout of the
underlying HW context image. Therefore, enabling OA on an already active
exec_queue (as currently implemented in xe) is an invalid operation and can
cause hangs. Therefore, disallow OA from being enabled on active
exec_queue's (here by active we mean a context on which submissions have
previously happened).

Transition from 1 -> 0 for this bit was disallowed in
'0c8650b09a36 ("drm/xe/oa: Don't reset OAC_CONTEXT_ENABLE on OA stream
close")'. Here we disallow the 0 -> 1 transition on active contexts.

Bspec: 60314
Fixes: 2f4a730fcd2d ("drm/xe/oa: Add OAR support")
Cc: stable at vger.kernel.org
Signed-off-by: Ashutosh Dixit <ashutosh.dixit at intel.com>
---
 drivers/gpu/drm/xe/xe_guc_submit.c |  2 +-
 drivers/gpu/drm/xe/xe_guc_submit.h |  1 +
 drivers/gpu/drm/xe/xe_oa.c         | 11 +++++++++++
 3 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/xe/xe_guc_submit.c b/drivers/gpu/drm/xe/xe_guc_submit.c
index 9e0f86f3778b2..5c285d966fd5c 100644
--- a/drivers/gpu/drm/xe/xe_guc_submit.c
+++ b/drivers/gpu/drm/xe/xe_guc_submit.c
@@ -83,7 +83,7 @@ static void clear_exec_queue_registered(struct xe_exec_queue *q)
 	atomic_and(~EXEC_QUEUE_STATE_REGISTERED, &q->guc->state);
 }
 
-static bool exec_queue_enabled(struct xe_exec_queue *q)
+bool exec_queue_enabled(struct xe_exec_queue *q)
 {
 	return atomic_read(&q->guc->state) & EXEC_QUEUE_STATE_ENABLED;
 }
diff --git a/drivers/gpu/drm/xe/xe_guc_submit.h b/drivers/gpu/drm/xe/xe_guc_submit.h
index 9b71a986c6ca6..a3bde061dd53c 100644
--- a/drivers/gpu/drm/xe/xe_guc_submit.h
+++ b/drivers/gpu/drm/xe/xe_guc_submit.h
@@ -12,6 +12,7 @@ struct drm_printer;
 struct xe_exec_queue;
 struct xe_guc;
 
+bool exec_queue_enabled(struct xe_exec_queue *q);
 int xe_guc_submit_init(struct xe_guc *guc, unsigned int num_ids);
 
 int xe_guc_submit_reset_prepare(struct xe_guc *guc);
diff --git a/drivers/gpu/drm/xe/xe_oa.c b/drivers/gpu/drm/xe/xe_oa.c
index fd2ffe8df1561..b0692b8ca0a3d 100644
--- a/drivers/gpu/drm/xe/xe_oa.c
+++ b/drivers/gpu/drm/xe/xe_oa.c
@@ -28,6 +28,7 @@
 #include "xe_gt_mcr.h"
 #include "xe_gt_printk.h"
 #include "xe_guc_pc.h"
+#include "xe_guc_submit.h"
 #include "xe_lrc.h"
 #include "xe_macros.h"
 #include "xe_mmio.h"
@@ -2064,6 +2065,16 @@ int xe_oa_stream_open_ioctl(struct drm_device *dev, u64 data, struct drm_file *f
 		if (XE_IOCTL_DBG(oa->xe, !param.exec_q))
 			return -ENOENT;
 
+		/*
+		 * Disallow OA from being enabled on active exec_queue's. Enabling OA toggles
+		 * the OAC_CONTEXT_ENABLE bit in CTXT_SR_CTL register, which changes the size
+		 * and layout of the underlying HW context image and can cause hangs.
+		 */
+		if (XE_IOCTL_DBG(oa->xe, exec_queue_enabled(param.exec_q))) {
+			ret = -EADDRINUSE;
+			goto err_exec_q;
+		}
+
 		if (param.exec_q->width > 1)
 			drm_dbg(&oa->xe->drm, "exec_q->width > 1, programming only exec_q->lrc[0]\n");
 	}
-- 
2.41.0