On Wed, Sep 25, 2024 at 9:58 PM Clément Léger <cle...@rivosinc.com> wrote:
>
> When the Ssdbltrp extension is enabled, SSTATUS.SDT field is cleared
> when executing sret. When executing mret/mnret, SSTATUS.SDT is cleared
> when returning to U, VS or VU and VSSTATUS.SDT is cleared when returning
> to VU from HS.
I don't see mret being mentioned in the spec. Where do you see that
V/SSTATUS.SDT should be cleared?
Alistair
>
> Signed-off-by: Clément Léger <cle...@rivosinc.com>
> ---
> target/riscv/op_helper.c | 35 ++++++++++++++++++++++++++++++++++-
> 1 file changed, 34 insertions(+), 1 deletion(-)
>
> diff --git a/target/riscv/op_helper.c b/target/riscv/op_helper.c
> index 6895c7596b..00b6f75102 100644
> --- a/target/riscv/op_helper.c
> +++ b/target/riscv/op_helper.c
> @@ -287,6 +287,18 @@ target_ulong helper_sret(CPURISCVState *env)
> get_field(mstatus, MSTATUS_SPIE));
> mstatus = set_field(mstatus, MSTATUS_SPIE, 1);
> mstatus = set_field(mstatus, MSTATUS_SPP, PRV_U);
> +
> + if (riscv_cpu_cfg(env)->ext_ssdbltrp) {
> + if (riscv_has_ext(env, RVH)) {
> + target_ulong prev_vu = get_field(env->hstatus, HSTATUS_SPV) &&
> + prev_priv == PRV_U;
> + /* Returning to VU from HS, vsstatus.sdt = 0 */
> + if (!env->virt_enabled && prev_vu) {
> + env->vsstatus = set_field(env->vsstatus, MSTATUS_SDT, 0);
> + }
> + }
> + mstatus = set_field(mstatus, MSTATUS_SDT, 0);
> + }
> if (env->priv_ver >= PRIV_VERSION_1_12_0) {
> mstatus = set_field(mstatus, MSTATUS_MPRV, 0);
> }
> @@ -297,7 +309,6 @@ target_ulong helper_sret(CPURISCVState *env)
> target_ulong hstatus = env->hstatus;
>
> prev_virt = get_field(hstatus, HSTATUS_SPV);
> -
> hstatus = set_field(hstatus, HSTATUS_SPV, 0);
>
> env->hstatus = hstatus;
> @@ -328,6 +339,22 @@ static void check_ret_from_m_mode(CPURISCVState *env,
> target_ulong retpc,
> riscv_raise_exception(env, RISCV_EXCP_INST_ACCESS_FAULT, GETPC());
> }
> }
> +static target_ulong ssdbltrp_mxret(CPURISCVState *env, target_ulong mstatus,
> + target_ulong prev_priv,
> + target_ulong prev_virt)
> +{
> + /* If returning to U, VS or VU, sstatus.sdt = 0 */
> + if (prev_priv == PRV_U || (prev_virt &&
> + (prev_priv == PRV_S || prev_priv == PRV_U))) {
> + mstatus = set_field(mstatus, MSTATUS_SDT, 0);
> + /* If returning to VU, vsstatus.sdt = 0 */
> + if (prev_virt && prev_priv == PRV_U) {
> + env->vsstatus = set_field(env->vsstatus, MSTATUS_SDT, 0);
> + }
> + }
> +
> + return mstatus;
> +}
>
> target_ulong helper_mret(CPURISCVState *env)
> {
> @@ -345,6 +372,9 @@ target_ulong helper_mret(CPURISCVState *env)
> mstatus = set_field(mstatus, MSTATUS_MPP,
> riscv_has_ext(env, RVU) ? PRV_U : PRV_M);
> mstatus = set_field(mstatus, MSTATUS_MPV, 0);
> + if (riscv_cpu_cfg(env)->ext_ssdbltrp) {
> + mstatus = ssdbltrp_mxret(env, mstatus, prev_priv, prev_virt);
> + }
> if ((env->priv_ver >= PRIV_VERSION_1_12_0) && (prev_priv != PRV_M)) {
> mstatus = set_field(mstatus, MSTATUS_MPRV, 0);
> }
> @@ -382,6 +412,9 @@ target_ulong helper_mnret(CPURISCVState *env)
> if (prev_priv < PRV_M) {
> env->mstatus = set_field(env->mstatus, MSTATUS_MPRV, false);
> }
> + if (riscv_cpu_cfg(env)->ext_ssdbltrp) {
> + env->mstatus = ssdbltrp_mxret(env, env->mstatus, prev_priv,
> prev_virt);
> + }
>
> if (riscv_has_ext(env, RVH) && prev_virt) {
> riscv_cpu_swap_hypervisor_regs(env);
> --
> 2.45.2
>
>
