CSR: sstatus.fs should be read-only zero

NutShell does not have F/D extensions. FS is read-only zero.
OSCPU · May 14, 2024 · b9fef3a · b9fef3a
1 parent 7810deb
commit b9fef3a
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diff --git a/ready-to-run/riscv64-nemu-interpreter-so b/ready-to-run/riscv64-nemu-interpreter-so
diff --git a/src/main/scala/nutcore/backend/fu/CSR.scala b/src/main/scala/nutcore/backend/fu/CSR.scala
@@ -336,7 +336,13 @@ class CSR(implicit val p: NutCoreConfig) extends NutCoreModule with HasCSRConst{
   // Superviser-Level CSRs
 
   // val sstatus = RegInit(UInt(XLEN.W), "h00000000".U)
-  val sstatusWmask = "hc6122".U(64.W)
+  val sstatusWmask = (~ZeroExt((
+    GenMask(63, 20)  | // SD, WPRI, UXL, WPRI
+    GenMask(17, 9)   | // WPRI, XS, FS, WPRI, VS
+    GenMask(7, 6)    | // WPRI, UBE
+    GenMask(4, 2)    | // WPRI
+    GenMask(0)         // WPRI
+  ), 64)).asUInt
   // Sstatus Write Mask
   // -------------------------------------------------------
   //    19           9   5     2