On 5/29/2026 2:57 PM, Brian Cain wrote:
> From: Brian Cain <[email protected]>
>
> The hardware-assisted scheduler helps manage tasks on the run queue
> and interrupt steering.
>
> Signed-off-by: Brian Cain <[email protected]>
> ---
> target/hexagon/op_helper.c | 77 ++++++++++++++++++++++++++++++++++++++
> 1 file changed, 77 insertions(+)
>
> diff --git a/target/hexagon/op_helper.c b/target/hexagon/op_helper.c
> index 64f1fb2043f..82062a2f802 100644
> --- a/target/hexagon/op_helper.c
> +++ b/target/hexagon/op_helper.c
> @@ -1589,6 +1589,64 @@ static void hexagon_wait_thread(CPUHexagonState *env,
> uint32_t PC)
> cpu_interrupt(cs, CPU_INTERRUPT_HALT);
> }
>
> +static inline QEMU_ALWAYS_INLINE void resched(CPUHexagonState *env)
> +{
> + uint32_t schedcfg;
> + uint32_t schedcfg_en;
> + int int_number;
> + CPUState *cs;
> + uint32_t lowest_th_prio = 0; /* 0 is highest prio */
> + uint32_t bestwait_reg;
> + uint32_t best_prio;
> + HexagonCPU *cpu;
> +
> + BQL_LOCK_GUARD();
> + qemu_log_mask(CPU_LOG_INT, "%s: check resched\n", __func__);
> + cpu = env_archcpu(env);
> + schedcfg = cpu->globalregs ?
> + hexagon_globalreg_read(cpu->globalregs, HEX_SREG_SCHEDCFG,
> + env->threadId) : 0;
> + schedcfg_en = GET_FIELD(SCHEDCFG_EN, schedcfg);
> + int_number = GET_FIELD(SCHEDCFG_INTNO, schedcfg);
> +
> + if (!schedcfg_en) {
> + return;
> + }
> +
Is that really a noop in this case?
Or should it trigger an exception if sched is not enabled?
> + CPU_FOREACH(cs) {
> + HexagonCPU *thread = HEXAGON_CPU(cs);
> + CPUHexagonState *thread_env = &(thread->env);
> + uint32_t th_prio = GET_FIELD(
> + STID_PRIO, thread_env->t_sreg[HEX_SREG_STID]);
> + if (!hexagon_thread_is_enabled(thread_env)) {
> + continue;
> + }
> +
> + lowest_th_prio = (lowest_th_prio > th_prio)
> + ? lowest_th_prio
> + : th_prio;
> + }
> +
> + bestwait_reg = cpu->globalregs ?
> + hexagon_globalreg_read(cpu->globalregs, HEX_SREG_BESTWAIT,
> + env->threadId) : 0;
> + best_prio = GET_FIELD(BESTWAIT_PRIO, bestwait_reg);
> +
> + /*
> + * If the lowest priority thread is lower priority than the
> + * value in the BESTWAIT register, we must raise the reschedule
> + * interrupt on the lowest priority thread.
> + */
> + if (lowest_th_prio > best_prio) {
> + qemu_log_mask(CPU_LOG_INT,
> + "%s: raising resched int %u,"
> + " cur PC 0x%" PRIx32 "\n",
> + __func__, (unsigned)int_number, env->gpr[HEX_REG_PC]);
> + SET_SYSTEM_FIELD(env, HEX_SREG_BESTWAIT, BESTWAIT_PRIO, ~0);
> + hex_raise_interrupts(env, 1 << int_number, CPU_INTERRUPT_SWI);
> + }
> +}
> +
> void HELPER(wait)(CPUHexagonState *env, uint32_t PC)
> {
> BQL_LOCK_GUARD();
> @@ -1697,8 +1755,27 @@ uint64_t HELPER(greg_read_pair)(CPUHexagonState *env,
> uint32_t reg)
> g_assert_not_reached();
> }
>
> +/*
> + * setprio/resched - hardware-assisted scheduler helpers for managing
> + * the run queue and interrupt steering.
> + */
> void HELPER(setprio)(CPUHexagonState *env, uint32_t thread, uint32_t prio)
> {
> + CPUState *cs;
> +
> + BQL_LOCK_GUARD();
> + CPU_FOREACH(cs) {
> + HexagonCPU *found_cpu = HEXAGON_CPU(cs);
> + CPUHexagonState *found_env = &found_cpu->env;
> + if (thread == found_env->threadId) {
> + SET_SYSTEM_FIELD(found_env, HEX_SREG_STID, STID_PRIO, prio);
> + qemu_log_mask(CPU_LOG_INT,
> + "%s: tid %" PRIu32 " prio = 0x%" PRIx32 "\n",
> + __func__, found_env->threadId, prio);
> + resched(env);
> + return;
> + }
> + }
> g_assert_not_reached();
> }
>
