1 files changed, 22 insertions, 0 deletions
diff --git a/kernel/main.c b/kernel/main.c
index 458ba36..6902b48 100644
--- a/kernel/main.c
+++ b/kernel/main.c
@@ -907,6 +907,28 @@ static ssize_t nv_vgpu_vfio_dev_write(struct vfio_device *vdev, const char __use
 
 		if (copy_from_user(vgpu->bars[1].vaddr + bar1_off, buf, count))
 			return -EFAULT;
+		/*
+		 * SESSION 154 r1506: the X screen (VA 0x120400000, 900 pages)
+		 * is the BAR1 FB shadow at 0x200000. Guest CPU writes into
+		 * that range are either the X server's own fills (expected)
+		 * or another client's BAR1 upload that overlaps the screen
+		 * allocation (the shader-cache collision). Name them so the
+		 * owner of the pollution is measured, not inferred.
+		 */
+		{
+			static u32 bar1_scr_log;
+
+			if (bar1_off >= 0x200000u && bar1_off < 0x600000u &&
+			    bar1_scr_log < 64u && count <= 8) {
+				u64 v = 0;
+
+				memcpy(&v, vgpu->bars[1].vaddr + bar1_off,
+				       count);
+				pr_info("vgsp: BAR1-SCREEN-WRITE off=0x%llx size=%zu val=0x%llx (screen range 0x200000-0x584000)\n",
+					bar1_off, count, v);
+				bar1_scr_log++;
+			}
+		}
 		*ppos += count;
 		return count;
 	}