[PATCH qemu 05/11] [ot] target/riscv: add custom mtvec CSR management

[~lexbaileylowrisc]

From: Emmanuel Blot <eb...@rivosinc.com>

Signed-off-by: Emmanuel Blot <eb...@rivosinc.com>
---
 target/riscv/ibex_csr.c | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/target/riscv/ibex_csr.c b/target/riscv/ibex_csr.c
index d62638bbfb..a6e815e782 100644
--- a/target/riscv/ibex_csr.c
+++ b/target/riscv/ibex_csr.c
@@ -69,7 +69,37 @@ static RISCVException any(CPURISCVState *env, int csrno)
     return RISCV_EXCP_NONE;
 }
 
+static RISCVException read_mtvec(CPURISCVState *env, int csrno,
+                                 target_ulong *val)
+{
+    *val = env->mtvec;
+
+    return RISCV_EXCP_NONE;
+}
+
+static RISCVException write_mtvec(CPURISCVState *env, int csrno,
+                                  target_ulong val, uintptr_t a)
+{
+    /* bits [1:0] encode mode; Ibex only supports 1 = vectored */
+    if ((val & 3u) != 1u) {
+        qemu_log_mask(LOG_UNIMP,
+            "CSR_MTVEC: reserved mode not supported 0x" TARGET_FMT_lx "\n",
+            val);
+        /* WARL */
+        return RISCV_EXCP_NONE;
+    }
+
+    /* bits [7:2] are always 0, address should be aligned in 256 bytes */
+    env->mtvec = val & ~0xFCu;
+
+    return RISCV_EXCP_NONE;
+}
+
 const RISCVCSR ibex_csr_list[] = {
+    {
+        .csrno = CSR_MTVEC,
+        .csr_ops = { "mtvec", any, &read_mtvec, &write_mtvec },
+    },
     {
         .csrno = CSR_CPUCTRLSTS,
         .csr_ops = { "cpuctrlsts", any, &read_cpuctrlsts, &write_cpuctrlsts },
-- 
2.49.1