target/riscv: rvk: add CSR support for Zkr

 - add SEED CSR which must be accessed with a read-write instruction:
   A read-only instruction such as CSRRS/CSRRC with rs1=x0 or CSRRSI/CSRRCI
with uimm=0 will raise an illegal instruction exception.
 - add USEED, SSEED fields for MSECCFG CSR

Co-authored-by: Ruibo Lu <luruibo2000@163.com>
Co-authored-by: Zewen Ye <lustrew@foxmail.com>
Signed-off-by: Weiwei Li <liweiwei@iscas.ac.cn>
Signed-off-by: Junqiang Wang <wangjunqiang@iscas.ac.cn>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-Id: <20220423023510.30794-13-liweiwei@iscas.ac.cn>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>

1 files changed, 9 insertions, 0 deletions

diff --git a/target/riscv/op_helper.c b/target/riscv/op_helper.c
index df35736883..09f1f5185d 100644
--- a/target/riscv/op_helper.c
+++ b/target/riscv/op_helper.c
@@ -39,6 +39,15 @@ void helper_raise_exception(CPURISCVState *env, uint32_t exception)
 
 target_ulong helper_csrr(CPURISCVState *env, int csr)
 {
+    /*
+     * The seed CSR must be accessed with a read-write instruction. A
+     * read-only instruction such as CSRRS/CSRRC with rs1=x0 or CSRRSI/
+     * CSRRCI with uimm=0 will raise an illegal instruction exception.
+     */
+    if (csr == CSR_SEED) {
+        riscv_raise_exception(env, RISCV_EXCP_ILLEGAL_INST, GETPC());
+    }
+
     target_ulong val = 0;
     RISCVException ret = riscv_csrrw(env, csr, &val, 0, 0);