1 files changed, 79 insertions, 0 deletions
diff --git a/target/riscv/th_csr.c b/target/riscv/th_csr.c
new file mode 100644
index 0000000000..6c970d4e81
--- /dev/null
+++ b/target/riscv/th_csr.c
@@ -0,0 +1,79 @@
+/*
+ * T-Head-specific CSRs.
+ *
+ * Copyright (c) 2024 VRULL GmbH
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2 or later, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "qemu/osdep.h"
+#include "cpu.h"
+#include "cpu_vendorid.h"
+
+#define CSR_TH_SXSTATUS 0x5c0
+
+/* TH_SXSTATUS bits */
+#define TH_SXSTATUS_UCME        BIT(16)
+#define TH_SXSTATUS_MAEE        BIT(21)
+#define TH_SXSTATUS_THEADISAEE  BIT(22)
+
+typedef struct {
+    int csrno;
+    int (*insertion_test)(RISCVCPU *cpu);
+    riscv_csr_operations csr_ops;
+} riscv_csr;
+
+static RISCVException smode(CPURISCVState *env, int csrno)
+{
+    if (riscv_has_ext(env, RVS)) {
+        return RISCV_EXCP_NONE;
+    }
+
+    return RISCV_EXCP_ILLEGAL_INST;
+}
+
+static int test_thead_mvendorid(RISCVCPU *cpu)
+{
+    if (cpu->cfg.mvendorid != THEAD_VENDOR_ID) {
+        return -1;
+    }
+
+    return 0;
+}
+
+static RISCVException read_th_sxstatus(CPURISCVState *env, int csrno,
+                                       target_ulong *val)
+{
+    /* We don't set MAEE here, because QEMU does not implement MAEE. */
+    *val = TH_SXSTATUS_UCME | TH_SXSTATUS_THEADISAEE;
+    return RISCV_EXCP_NONE;
+}
+
+static riscv_csr th_csr_list[] = {
+    {
+        .csrno = CSR_TH_SXSTATUS,
+        .insertion_test = test_thead_mvendorid,
+        .csr_ops = { "th.sxstatus", smode, read_th_sxstatus }
+    }
+};
+
+void th_register_custom_csrs(RISCVCPU *cpu)
+{
+    for (size_t i = 0; i < ARRAY_SIZE(th_csr_list); i++) {
+        int csrno = th_csr_list[i].csrno;
+        riscv_csr_operations *csr_ops = &th_csr_list[i].csr_ops;
+        if (!th_csr_list[i].insertion_test(cpu)) {
+            riscv_set_csr_ops(csrno, csr_ops);
+        }
+    }
+}