releases/6.17.5/drm-amdgpu-handle-wrap-around-in-reemit-handling.patch

From 7729492571a4fb27da7663df270df132b9e169d0 Mon Sep 17 00:00:00 2001
From: Sasha Levin <sashal@kernel.org>
Date: Mon, 15 Sep 2025 12:37:32 -0400
Subject: drm/amdgpu: handle wrap around in reemit handling
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

From: Alex Deucher <alexander.deucher@amd.com>

[ Upstream commit 1f22fcb88bfef26a966e9eb242c692c6bf253d47 ]

Compare the sequence numbers directly.

Fixes: 77cc0da39c7c ("drm/amdgpu: track ring state associated with a fence")
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c
index 9e7506965cab2..bb17af79c24a6 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c
@@ -791,14 +791,19 @@ void amdgpu_ring_backup_unprocessed_commands(struct amdgpu_ring *ring,
 	struct dma_fence *unprocessed;
 	struct dma_fence __rcu **ptr;
 	struct amdgpu_fence *fence;
-	u64 wptr, i, seqno;
+	u64 wptr;
+	u32 seq, last_seq;
 
-	seqno = amdgpu_fence_read(ring);
+	last_seq = amdgpu_fence_read(ring) & ring->fence_drv.num_fences_mask;
+	seq = ring->fence_drv.sync_seq & ring->fence_drv.num_fences_mask;
 	wptr = ring->fence_drv.signalled_wptr;
 	ring->ring_backup_entries_to_copy = 0;
 
-	for (i = seqno + 1; i <= ring->fence_drv.sync_seq; ++i) {
-		ptr = &ring->fence_drv.fences[i & ring->fence_drv.num_fences_mask];
+	do {
+		last_seq++;
+		last_seq &= ring->fence_drv.num_fences_mask;
+
+		ptr = &ring->fence_drv.fences[last_seq];
 		rcu_read_lock();
 		unprocessed = rcu_dereference(*ptr);
 
@@ -814,7 +819,7 @@ void amdgpu_ring_backup_unprocessed_commands(struct amdgpu_ring *ring,
 			wptr = fence->wptr;
 		}
 		rcu_read_unlock();
-	}
+	} while (last_seq != seq);
 }
 
 /*
-- 
2.51.0