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target/riscv: fix wfi exception behavior 

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 <josemartins90@gmail.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-id: 20210420213656.85148-1-josemartins90@gmail.com
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>
This commit is contained in:
Jose Martins 2021-04-20 22:36:56 +01:00 committed by Alistair Francis
parent 143897b501
commit 719f0f603c
2 changed files with 9 additions and 3 deletions
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1
target/riscv/cpu_bits.h
View File

@ -390,6 +390,7 @@
#define HSTATUS_HU 0x00000200
#define HSTATUS_VGEIN 0x0003F000
#define HSTATUS_VTVM 0x00100000
#define HSTATUS_VTW 0x00200000
#define HSTATUS_VTSR 0x00400000
#define HSTATUS_VSXL 0x300000000

11
target/riscv/op_helper.c
View File

@ -177,10 +177,15 @@ 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;