Unverified Commit b8643bd6 authored by Michael Clark's avatar Michael Clark
Browse files

RISC-V: No traps on writes to misa,minstret,mcycle 



These fields are marked WARL (Write Any Values, Reads
Legal Values) in the RISC-V Privileged Architecture
Specification so instead of raising exceptions,
illegal writes are silently dropped.

Cc: Sagar Karandikar <sagark@eecs.berkeley.edu>
Cc: Bastian Koppelmann <kbastian@mail.uni-paderborn.de>
Cc: Palmer Dabbelt <palmer@sifive.com>
Cc: Alistair Francis <Alistair.Francis@wdc.com>
Signed-off-by: default avatarMichael Clark <mjc@sifive.com>
parent 1d1ee552

target/riscv/op_helper.c

+13 −12
Original line number Diff line number Diff line
@@ -213,17 +213,19 @@ void csr_write_helper(CPURISCVState *env, target_ulong val_to_write, 
        break;

    }

    case CSR_MINSTRET:

        qemu_log_mask(LOG_UNIMP, "CSR_MINSTRET: write not implemented");

        goto do_illegal;

        /* minstret is WARL so unsupported writes are ignored */

        break;

    case CSR_MCYCLE:

        qemu_log_mask(LOG_UNIMP, "CSR_MCYCLE: write not implemented");

        goto do_illegal;

        /* mcycle is WARL so unsupported writes are ignored */

        break;

#if defined(TARGET_RISCV32)

    case CSR_MINSTRETH:

        qemu_log_mask(LOG_UNIMP, "CSR_MINSTRETH: write not implemented");

        goto do_illegal;

        /* minstreth is WARL so unsupported writes are ignored */

        break;

    case CSR_MCYCLEH:

        qemu_log_mask(LOG_UNIMP, "CSR_MCYCLEH: write not implemented");

        goto do_illegal;

        /* mcycleh is WARL so unsupported writes are ignored */

        break;

#endif

    case CSR_MUCOUNTEREN:

        if (env->priv_ver <= PRIV_VERSION_1_09_1) {

            env->scounteren = val_to_write;
@@ -337,10 +339,9 @@ void csr_write_helper(CPURISCVState *env, target_ulong val_to_write, 
    case CSR_MBADADDR:

        env->mbadaddr = val_to_write;

        break;

    case CSR_MISA: {

        qemu_log_mask(LOG_UNIMP, "CSR_MISA: misa writes not supported");

        goto do_illegal;

    }

    case CSR_MISA:

        /* misa is WARL so unsupported writes are ignored */

        break;

    case CSR_PMPCFG0:

    case CSR_PMPCFG1:

    case CSR_PMPCFG2: