On Wed, Apr 21, 2021 at 7:37 AM Jose Martins <[email protected]> wrote: > > The wfi exception trigger behavior should take into account user mode, > hstatus.vtw, and the fact the an wfi might raise different types of > exceptions depending on various factors: > > If supervisor mode is not present: > > - an illegal instruction exception should be generated if user mode > executes and wfi instruction and mstatus.tw = 1. > > If supervisor mode is present: > > - when a wfi instruction is executed, an illegal exception should be triggered > if either the current mode is user or the mode is supervisor and mstatus.tw is > set. > > Plus, if the hypervisor extensions are enabled: > > - a virtual instruction exception should be raised when a wfi is executed from > virtual-user or virtual-supervisor and hstatus.vtw is set. > > Signed-off-by: Jose Martins <[email protected]>
Reviewed-by: Alistair Francis <[email protected]> Alistair > --- > Alistair, I hope you've agreed with my argumentis for the previous version > of the patch. As promised, I submit this version which takes into account M/U > only harts. It checks for the presence of the RVS extension. If it is > not present mstatus.tw takes effect over the exection of wfi in user > mode. > > target/riscv/cpu_bits.h | 1 + > target/riscv/op_helper.c | 11 ++++++++--- > 2 files changed, 9 insertions(+), 3 deletions(-) > > diff --git a/target/riscv/cpu_bits.h b/target/riscv/cpu_bits.h > index 24b24c69c5..ed8b97c788 100644 > --- a/target/riscv/cpu_bits.h > +++ b/target/riscv/cpu_bits.h > @@ -436,6 +436,7 @@ > #define HSTATUS_HU 0x00000200 > #define HSTATUS_VGEIN 0x0003F000 > #define HSTATUS_VTVM 0x00100000 > +#define HSTATUS_VTW 0x00200000 > #define HSTATUS_VTSR 0x00400000 > #if defined(TARGET_RISCV64) > #define HSTATUS_VSXL 0x300000000 > diff --git a/target/riscv/op_helper.c b/target/riscv/op_helper.c > index d55def76cf..15982a7a33 100644 > --- a/target/riscv/op_helper.c > +++ b/target/riscv/op_helper.c > @@ -173,10 +173,15 @@ target_ulong helper_mret(CPURISCVState *env, > target_ulong cpu_pc_deb) > void helper_wfi(CPURISCVState *env) > { > CPUState *cs = env_cpu(env); > + bool rvs = riscv_has_ext(env, RVS); > + bool prv_u = env->priv == PRV_U; > + bool prv_s = env->priv == PRV_S; > > - if ((env->priv == PRV_S && > - get_field(env->mstatus, MSTATUS_TW)) || > - riscv_cpu_virt_enabled(env)) { > + if (((prv_s || (!rvs && prv_u)) && get_field(env->mstatus, MSTATUS_TW)) > || > + (rvs && prv_u && !riscv_cpu_virt_enabled(env))) { > + riscv_raise_exception(env, RISCV_EXCP_ILLEGAL_INST, GETPC()); > + } else if (riscv_cpu_virt_enabled(env) && (prv_u || > + (prv_s && get_field(env->hstatus, HSTATUS_VTW)))) { > riscv_raise_exception(env, RISCV_EXCP_VIRT_INSTRUCTION_FAULT, > GETPC()); > } else { > cs->halted = 1; > -- > 2.25.1 > >
