On Wed, Apr 25, 2018 at 5:08 PM Michael Clark <m...@sifive.com> wrote:
> Vectored traps for asynchrounous interrupts are optional.
> The mtvec/stvec mode field is WARL and hence does not trap
> if an illegal value is written. Illegal values are ignored.
> Later we can add RISCV_FEATURE_VECTORED_TRAPS however
> until then the correct behavior for WARL (Write Any, Read
> Legal) fields is to drop writes to unsupported bits.
> Cc: Sagar Karandikar <sag...@eecs.berkeley.edu>
> Cc: Bastian Koppelmann <kbast...@mail.uni-paderborn.de>
> Cc: Palmer Dabbelt <pal...@sifive.com>
> Cc: Alistair Francis <alistair.fran...@wdc.com>
> Signed-off-by: Michael Clark <m...@sifive.com>
> ---
> target/riscv/op_helper.c | 14 ++++++--------
> 1 file changed, 6 insertions(+), 8 deletions(-)
> diff --git a/target/riscv/op_helper.c b/target/riscv/op_helper.c
> index 101dac1..828f20c 100644
> --- a/target/riscv/op_helper.c
> +++ b/target/riscv/op_helper.c
> @@ -276,11 +276,10 @@ void csr_write_helper(CPURISCVState *env,
target_ulong val_to_write,
> env->sepc = val_to_write;
> break;
> case CSR_STVEC:
> - if (val_to_write & 1) {
> - qemu_log_mask(LOG_UNIMP, "CSR_STVEC: vectored traps not
supported");
Should the unimplemented log be removed?
Alistair
> - goto do_illegal;
> + /* we do not support vectored traps for asynchrounous interrupts
*/
> + if ((val_to_write & 3) == 0) {
> + env->stvec = val_to_write >> 2 << 2;
> }
> - env->stvec = val_to_write >> 2 << 2;
> break;
> case CSR_SCOUNTEREN:
> env->scounteren = val_to_write;
> @@ -298,11 +297,10 @@ void csr_write_helper(CPURISCVState *env,
target_ulong val_to_write,
> env->mepc = val_to_write;
> break;
> case CSR_MTVEC:
> - if (val_to_write & 1) {
> - qemu_log_mask(LOG_UNIMP, "CSR_MTVEC: vectored traps not
supported");
> - goto do_illegal;
> + /* we do not support vectored traps for asynchrounous interrupts
*/
> + if ((val_to_write & 3) == 0) {
> + env->mtvec = val_to_write >> 2 << 2;
> }
> - env->mtvec = val_to_write >> 2 << 2;
> break;
> case CSR_MCOUNTEREN:
> env->mcounteren = val_to_write;
> --
> 2.7.0
