diff options
Diffstat (limited to 'target/riscv/csr.c')
| -rw-r--r-- | target/riscv/csr.c | 54 |
1 files changed, 53 insertions, 1 deletions
diff --git a/target/riscv/csr.c b/target/riscv/csr.c index e2bd374..e72fcf1 100644 --- a/target/riscv/csr.c +++ b/target/riscv/csr.c @@ -332,6 +332,58 @@ static int read_misa(CPURISCVState *env, int csrno, target_ulong *val) return 0; } +static int write_misa(CPURISCVState *env, int csrno, target_ulong val) +{ + if (!riscv_feature(env, RISCV_FEATURE_MISA)) { + /* drop write to misa */ + return 0; + } + + /* 'I' or 'E' must be present */ + if (!(val & (RVI | RVE))) { + /* It is not, drop write to misa */ + return 0; + } + + /* 'E' excludes all other extensions */ + if (val & RVE) { + /* when we support 'E' we can do "val = RVE;" however + * for now we just drop writes if 'E' is present. + */ + return 0; + } + + /* Mask extensions that are not supported by this hart */ + val &= env->misa_mask; + + /* Mask extensions that are not supported by QEMU */ + val &= (RVI | RVE | RVM | RVA | RVF | RVD | RVC | RVS | RVU); + + /* 'D' depends on 'F', so clear 'D' if 'F' is not present */ + if ((val & RVD) && !(val & RVF)) { + val &= ~RVD; + } + + /* Suppress 'C' if next instruction is not aligned + * TODO: this should check next_pc + */ + if ((val & RVC) && (GETPC() & ~3) != 0) { + val &= ~RVC; + } + + /* misa.MXL writes are not supported by QEMU */ + val = (env->misa & MISA_MXL) | (val & ~MISA_MXL); + + /* flush translation cache */ + if (val != env->misa) { + tb_flush(CPU(riscv_env_get_cpu(env))); + } + + env->misa = val; + + return 0; +} + static int read_medeleg(CPURISCVState *env, int csrno, target_ulong *val) { *val = env->medeleg; @@ -810,7 +862,7 @@ static riscv_csr_operations csr_ops[CSR_TABLE_SIZE] = { /* Machine Trap Setup */ [CSR_MSTATUS] = { any, read_mstatus, write_mstatus }, - [CSR_MISA] = { any, read_misa }, + [CSR_MISA] = { any, read_misa, write_misa }, [CSR_MIDELEG] = { any, read_mideleg, write_mideleg }, [CSR_MEDELEG] = { any, read_medeleg, write_medeleg }, [CSR_MIE] = { any, read_mie, write_mie }, |